This PDF file contains the front matter associated with SPIE Proceedings Volume 7720, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We have explored the possibility to extend the data transmission rate for standard 850-nm GaAs-based VCSELs beyond the 10 Gbit/s limit of today's commercially available directly-modulated devices. By sophisticated tailoring of the design for high-speed performance we demonstrate that 10 Gb/s is far from the upper limit. For example, the thermal conductivity of the bottom mirror is improved by the use of binary compounds, and the electrical parasitics are kept at a minimum by incorporating a large diameter double layered oxide aperture in the design. We also show that the intrinsic high speed performance is significantly improved by replacing the traditional GaAs QWs with strained InGaAs QWs in the active region. The best overall performance is achieved for a device with a 9 μm diameter oxide aperture, having in a threshold current of 0.6 mA, a maximum output power of 9 mW, a thermal resistance of 1.9 °C/mW, and a differential resistance of 80 Ω. The measured 3dB bandwidth exceeds 20 GHz, and we experimentally demonstrate that the device is capable of error-free transmission (BER<10^-12) under direct modulation at a record-high bit-rate of 32 Gb/s over 50 m of OM3 fiber at room temperature, and at 25 Gb/s over 100 m of OM3 fiber at 85 °C. We also demonstrate transmission at 40 Gb/s over 200 m of OM3+ fiber at room temperature using a subcarrier multiplexing scheme with a spectrally efficient 16 QAM modulation format. All transmission results were obtained with the VCSEL biased at current densities between 11-14 kA/cm², which is close to the 10 kA/cm² industry benchmark for reliability. Finally, we show that by a further reduction of the oxide capacitance and by reducing the photon lifetime using a shallow surface etch, a record bandwidth of 23 GHz for 850 nm VCSELs can be reached.

VCSELs continue to be widely deployed in data communication networks. The total bandwidth requirements continue to grow, resulting in higher data rates and utilization of both spatial and wavelength multiplexing. This paper will discuss recent results on VCSELs operating at aggregate speeds up to 1000Gbps as well as the prospects and results on extending to higher serial data rates.

Spatial transverse modes and polarization states are experimentally studied in single vertical cavity surface emitting lasers (VCSELs) and phased-locked VCSEL arrays emitting at 1.3μm wavelength. Analysis of the polarization-resolved near fields, far fields and emission spectra permit the observation of the competition between the different modes. Possible ways for increasing single mode power and spectral purity are discussed.

Vertical-cavity surface-emitting lasers (VCSELs) emitting at 894.6 nm wavelength have been fabricated for Cs-based atomic clock applications. For polarization control, a previously developed technique relying on the integration of a semiconducting surface grating in the top Bragg mirror of the VCSEL structure is employed. More specifically, we use a so-called inverted grating. The VCSELs are polarized orthogonal to the grating lines with no far-field diffraction side-lobes for sub-wavelength grating periods. Orthogonal polarization suppression ratios exceed 20 dB. The polarization stability has been investigated at different elevated substrate temperatures up to 80 °C, where the VCSEL remains polarization-stable even well above thermal roll-over. For the purpose of integration with the atomic clock microsystem, flip-chip-bondable VCSEL chips have been realized. Sub-mA threshold currents and sufficient output powers in the milliwatt range are achieved. The required modulation bandwidth of more than 5 GHz is reached at only 0.5mA bias. Maximum bandwidths above 10 GHz have been measured even at elevated temperatures up to 80 °C. Modulation current efficiency factors larger than 12 GHz/√mA are achieved at room temperature. Moreover, the intrinsic modulation characteristics of the VCSELs are investigated by precise curve fitting of measured small-signal modulation response curves and relative intensity noise spectra. A K-factor of less than 0.4 ns and a maximum 3 dB bandwidth exceeding 22 GHz are obtained.

The dynamics of a broad-area vertical-cavity surface-emitting laser (VCSEL) with frequency-selective feedback supporting bistable spatial solitons is analyzed experimentally and theoretically. The transient dynamics of a switch-on of a soliton induced by an external optical pulse shows strong self-pulsing at the external-cavity round-trip time with at least ten modes excited. The numerical analysis indicates an even broader bandwidth and a transient sweep of the center frequency. It is argued that mode-locking of spatial solitons is an interesting and viable way to achieve three-dimensional, spatio-temporal self-localization and that the transients observed are preliminary indications of a transient cavity light bullet in the dynamics, though on a non negligible background.

Auger recombination plays an important role in lasers operating in the long-wavelength regime (> 1 μm). Indeed, the Auger recombination time decreases exponentially with the inverse of the band gap energy and with temperature. A frequently used technique to estimate the Auger coefficient is the turn-on delay experiment, in which the time delay between the current pulse and the laser light pulse is evaluated. We reviewed the theory behind this experiment and found a discrepancy of the standard formulae used in the literature. This discrepancy occurs due to the assumption that the differential recombination time is independent of the carrier density, which is generally not justified. In particular, for short-wavelength lasers, it is expected that bimolecular recombination dominates, whereas for long-wavelength lasers, Auger recombination dominates. These two contributions can lead to additional linear and quadratic dependences of the differential recombination time on the carrier density. A general formula for the turn-on delay is thus derived, which explicitly includes capture, radiative and Auger recombination mechanisms. Analytical details for using this formula are given and it is shown how it reduces when a particular recombination process dominates. Estimations for the different recombination coefficients are found by fitting experimental data with the formula derived. This procedure is then applied to the case of long-wavelength vertical-cavity surface-emitting lasers (VCSELs) that incorporate InAlGaAs/InP systems in their active region.

A self-consistent pulse-operation model of an InP-based 1300-nm AlInGaAs vertical-cavity surface-emitting diode laser with filled-photonic-crystal is presented. It is shown that low threshold characteristics and strong transverse-mode discrimination can be simultaneously achieved for optimized photonic crystal structure for broad optical apertures.

We present the monolithic design, fabrication and properties of 850nm wavelength AlGaAs-GaAs-based transceiver chips with a stacked layer structure of a VCSEL and a PIN photodetector. Bidirectional data transmission via a single, two-side butt-coupled multimode fiber (MMF) is thus enabled. The approach aims at a miniaturization of transceiver chips in order to ensure compatibility with standard MMFs with core diameters of 50 and 62.5μm used predominantly in premises networks. These chips are supposed to be well suited for low-cost and compact half- and full-duplex interconnection at Gbit/s data rates over distances of a few hundred meters.

Optically-injected semiconductor lasers have been investigated for many years. The attention has nowadays shifted towards multi-section lasers as they provide new kinds of applications. Recently, an improved travelling-wave (TW) method for simulation of multi-section lasers was presented in which spatio-temporal effects were included. An automated analysis tool was presented for the simulated data to distinguish between different states of dynamics outside the locking bandwidth as this was not possible before. Here, a three-section tunable laser, with and without optical injection, is simulated with the improved TW method and two new results are found. Firstly, the penetration depth of the optical power inside the DBR section of a solitary three-section laser strongly depends on its position on the tuning characteristic curve. It is shown that even with a small variation of the carrier density in the tuning region a large variation of the penetration depth can be observed and, hence, the optical power emitted out of the grating section changes significantly. Secondly, the dynamics of an optically-injected tunable laser for middle and high injection strengths are presented and it is demonstrated that the locking bandwidth becomes symmetric around zero detuning and new regions of higher-order instabilities appear outside the locking region.

We study quantum dot mode locked lasers (QD MLL) under optical injection. For the experimental study we use slave lasers two-section monolithic InAs/GaAs QD devices with a repetition rate of about 9.4 GHz, emitting at 1.3 μm. A frequency resolved Mach-Zehnder gating (FRMZG) technique was utilised for the experimental study of the pulse intensity, phase and chirp. For numerical simulations we use a modified delay-differential model. We show experimentally improvement of the laser performance under injection and provide numerical locking ranges obtained with DDEBIFTOOL package.

We report an experimental and theoretical investigation of the effect of optical injection on the characteristics of optical pulses generated by gain-switching a 1550 nm single transverse mode vertical-cavity surface-emitting laser (VCSEL). Under continuous wave operation the VCSEL emits in a linear polarization along the whole current range. The experimental analysis of the effect of external optical injection on the timing jitter, maximum power, and pulse width of optical pulses generated by gain-switching the single mode VCSEL is performed for several repetition rates and for different values of the detuning between the frequency of the optical injection and the VCSEL. Experimental results show that for 1 GHz repetition frequency, jitter reductions greater than 70 % can be obtained over a 47 GHz frequency detuning range with a slight increase of 22% in pulse width with respect to the solitary case. A clear anticorrelation between the maximum power and pulse width is also obtained. A theoretical study is also performed by using a model that incorporates both spatial dependence of carrier density and optical field profiles. The two polarization modes are also taken into account in the model. The theoretical results are in good agreement with the experimental results.

The effectiveness of semiconductor optical amplifiers (SOAs) in restoring the power loss in the transmission in Optical Chaos Communications Systems has been experimentally studied. In-line optical amplification is shown to be effective in restoring the received optical power to enable successful message extraction at an authorised receiver. However, the in-line optical amplification can not totally compensate for the deterioration of the quality of the chaos synchronization and decoded message, which eavesdropper alert can be achieved by measuring the cross correlation coefficient.

We present an analysis of a semiconductor laser subject to filtered optical feedback from two filtering elements (2FOF). The motivation for this study comes from applications where two filters are used to control and stabilise the laser output. Compared to a laser with a single filtered optical feedback loop, the introduction of the second filter significantly influences the structure of the basic continuous-wave solutions, which are also known as external filtered modes (EFMs). We compute and represent the EFMs of the underlying delay differential equation model as surfaces in the space of frequency ω_s and inversion level N_s of the laser, and feedback phase difference dC_p. The quantity dC_p is a key parameter since it is associated with interference between the two filter fields and, hence, controls the effective feedback strength. We further show how the EFM surface in (ω_s, dC_p, N_s)-space changes upon variation of other filter parameters, in particular, the two delay times. Overall, the investigation of the EFM-surface provides a geometric approach to the multi-parameter analysis of the 2FOF laser, which allows for comprehensive insight into the solution structure and dynamics of the system.

We present an architecture tailored for the multiplexing of multiple optical chaotic carriers generated by semiconductor lasers with external optical cavities. Our setup can discriminate multiple chaotic signals with high spectral overlap. The various emitters are mutually globally coupled thanks to a shared optical feedback, which creates a multiplexed optical field. This field is then coherently and unidirectionally injected in the decoupled receivers, and allows each of them to synchronize on their respective emitter. Using this setup, it would be possible to transmit several messages and make a better use of the wide chaotic spectrum. In this paper, we demonstrate theoretically and numerically the possibility to synchronize two optical chaotic fields as a premise for the transmission of two messages. We also study the robustness of synchronization to parameter mismatch and noise, which are important issues in real field experiments.

We investigate both theoretically and experimentally the noise-induced transitions between the counter-rotating lasing modes of a semiconductor ring laser (SRL). Our experiments reveal that the residence time distribution (RTD) cannot be described by a simple one-parameter Arrhenius exponential law, due to the presence of two well-separated time scales in the process. Time-series of the mode-resolved power reveal an intricate mode-hopping dynamics and the connection between the time scales in the RTD and different mode-hopping scenarios. A theoretical approach is proposed in order to elucidate the origin of the two time scales, as well as the features of the mode-hopping events. We argue that the presence of two time-scales in the system is due to the finiteness of the noise intensity in the system which allows for diffusion between different folds of the invariant manifolds. Our approach is based on a double asymptotic reduction which is valid in the limit of slow dynamics and low noise-intensity. The theoretical predictions agree well with the results of numerical simulations and the experiments.

Phase-locked operation of an array of ten diode lasers is demonstrated in an extended-cavity using the Talbot self-imaging effect. An output power up to 1.7 W has been obtained. The extracavity coherent conversion of the multilobed array supermode into a Gaussian mode is investigated theoretically based on a binary phase grating. The best configuration results in a conversion efficiency of 83%. Experimentally, the conversion efficiency reaches 50% and is limited by the imperfect coherence of the laser array. We conclude that the conversion setup provides an actual measurement of the power in the selected array supermode.

This work presents a theoretical and experimental investigation on the improvement of complex low quality pulses obtained from a pulsed diode laser Gain-Switched (GS) optical sources by using a Highly Nonlinear Optical Loop Mirror (HNOLM) directly coupled to the diode laser source without any previous conditioning of the pulses. First, a design of the HNOLM device is evaluated. The proposed HNOLM is compact, containing 20 m of optical fiber and does not require any intermediate stage to process the pulses. The device is based on the use of a Microstructured Optical Fiber and a Highly Nonlinear Semiconductor Optical Amplifier. An experimental study of the achieved improvement of the quality of GS pulses is presented. The pulses have been characterized through the evaluation of their autocorrelation traces and a study using a Temporal Information Via Intensity (TIVI) algorithm. Results show that HNOLM provides direct compression and pulse shaping for picosecond complex pulses obtained from a DFB COTS laser operating within the 1550 nm window. The experimental observations are contrasted with a theoretical modeling of the system, and an excellent agreement is observed.

A monolithic device for the generation of tunable narrow linewidth millimeter-wave signal for wireless applications has been fabricated and characterized. The device consists of three mutually injected DFB lasers that are phase locked by Four Wave Mixing, and generate a beating signal at frequencies of 100-300 GHz.

Photonic transmission of microwave signals from a central office to remote base stations is a key functionality in broadband radio-over-fiber access networks. Because of chromatic dispersion, a strong fluctuation of the microwave power along fiber transmission happens to microwave-modulated optical carriers with double-sideband features. Therefore, optical single-sideband modulation characteristics are preferred. Direct modulation of a semiconductor laser is the simplest scheme for photonic microwave generation and transmission. However, the symmetric property of the laser in the modulation sideband intensity makes the scheme unattractive for radio-over-fiber applications. In this study, we apply the injection locking technique to the laser for optical single-sideband generation. Proper optical injection can drive the laser to the stable-locking dynamical state before entering the Hopf bifurcation. The field-carrier coupling of the injected laser is radically modified due to the dynamical interaction between the injection-shifted cavity resonance and the injection-imposed oscillation. Therefore, the relaxation resonance sidebands of the injected laser are considerably shifted in frequency and asymmetrically modified in intensity, the extent of which depends strongly on the injection condition. Under the range of our study, direct modulation of the injected laser can thus generate microwave signals that are broadly tunable up to 4 times its free-funning relaxation resonance frequency and are highly asymmetric up to 20 dB in modulation sidebands. The microwave frequency can be tuned over a broad range while keeping a similar level of modulation sideband asymmetry, or different levels of modulation sideband asymmetry can be obtained while keeping a similar microwave frequency. This adds the flexibility and re-configurability to the proposed system. No optical phase-locking electronics, no high driving voltages, and no narrow-bandwidth optical filters are necessary as in many other systems.

Semiconductor quantum-dots have been recently showing great promise for the generation of ultrashort pulses, forming the basis of very compact and efficient ultrafast laser sources. In this paper we discuss how the unique properties of quantum-dot materials can be exploited in novel and versatile mode-locking regimes in InAs/GaAs quantum-dot edge-emitting lasers, both in monolithic and external cavity configurations. We present the current status of our research on ultrashort pulse generation involving ground (1260nm) and excited-state (1180nm) transitions, as well as the recent progress in external-cavity broadband tunable quantum-dot lasers.

We analyze the dynamics of a mode-locked quantum-dot edge-emitting semiconductor laser consisting of reversely biased saturable absorber and forward biased amplifying sections. To describe spatial non-uniformity of laser parameters, optical fields and carrier distributions we use the traveling wave model, which takes into account carrier exchange processes between wetting layer and quantum dots. A comprehensive parameter study and an optical mode analysis of operation regimes are presented.

Hybrid mode-locking in monolithic quantum dot lasers is studied experimentally and theoretically. A strong asymmetry of the locking range with respect to the passive mode locking frequency is observed. The width of this range increases linearly with the modulation amplitude for all operating parameters. Maximum locking range found is 30 MHz. The results of a numerical analysis performed using a set of five delay-differential equations taking into account carrier exchange between quantum dots and wetting layer are in agreement with experiments and indicate that a spectral filtering element could improve locking characteristics. Asymptotic analysis of the dependence of the locking range on the laser parameters is performed with the help of a more simple laser model consisting of three delay differential equations.

Quantum-dot mode-locked lasers are injection-locked by coherent two-tone master sources. With optical injection the slave laser optical spectrum becomes narrowed and tunable via the master wavelength. Frequency-resolved Mach-Zehnder gating measurements performed to characterize slave laser pulses showed significantly improved pulse time-bandwidth product (TBP) with optical injection. Measurements of the modal optical linewidths of the injected laser demonstrated phase locking of all the slave laser modes to the master laser, which improved significantly the device timing jitter. Integrated over a 20 kHz-80 MHz range timing jitter values of 210 fs were achieved for small injection powers, close to the best reported results for the hybrid mode-locking of similar QD-MLLs.

Based on frequency resolved optical gating, a pulse shape and phase characterization of a monolithic-two-section, quantum-dot mode-locked laser (QD-MLL) at 1.3 μm, at a repetition rate of 40 GHz, is presented. The dynamics of the absorber and the gain section are investigated in detail. Increasing the gain current leads to an increase of mostly linear chirp inducing significant pulse broadening. The absorber dynamics, namely the sweep out time of the carriers of the QDs, is enhanced at larger reverse biases. The quantum confined stark effect (QCSE) however reduces the absorber efficiency. Thus the shortest pulse width occurs for medium voltages. Pulses generated by hybrid mode locking are compared to passive mode-locked ones. Only a slight suppression of the trailing part of the pulses is found. Simulations as well as experiments demonstrate that the linear part of the chirp can be easily compensated leading to pulse compression. A pulse width of 700 fs is achieved almost independent of operating conditions. Temperature changes of 8°C leads to pulse broadening of a few hundred femtoseconds. Pulse combs up to 160 Gbit/s are generated using optical time division multiplexing (OTDM). Eye diagrams and autocorrelation measurements prove the suitability of our approach.

In this contribution reverse emission state transition of a two-section quantum dot laser at a saturable absorber bias of zero volt (short circuit) is presented where lasing and mode-locking starts first on the energetically higher first excited-state (ES) and then, with increasing gain current, additional lasing and mode-locking on the energetically lower ground-state (GS) takes place. A huge coexistence regime as well as temporal simultaneity of both GS and ES mode-locking is experimentally confirmed. At the onset of two-state mode-locking shorter pulse widths are found for the GS as compared to the ES at the same gain current. A considerable shortening of the ES pulse widths is observed when GS mode-locking starts. These state-resolved emission dynamics are confirmed by time-domain travelling-wave equation modeling. Finally, by electrically shortening the saturable absorber via an external variable resistor, a resistor Self-Electro-Optical Devices (SEED) configuration is exploited and tailored emission state control is achieved.

In this paper the investigation of thermal properties of the optically pumped vertical external cavity surface emitting lasers (VECSEL) is reported. The experimental technique used is thermoreflectance. The original achievements of the paper include design and construction of experimental setups allowing the measurement of the temperature distributions on the surface of the operating VECSEL with and without heatspreader. The temperature increase in case of the VECSEL with SiC heatspreader is reduced by the factor of almost 10 in comparison to the VECSEL without the heatspreader. Additionally, the lowering of the temperature of lasing VECSEL was observed experimentally.

The layer structure of the gain element in an optically pumped semiconductor disk laser (OP-SDL) was designed for wide tunability. This was achieved by a parametric optimization of the structure, which in effect balanced the spectrally varying influence of the gain of the quantum wells, the longitudinal distribution of the standing wave lasing field in the structure, and the degree of resonance in the subcavity formed between the distributed Bragg reflector at the bottom and the air-semiconductor interface at the top. The quality measure in the optimization was the spectral reflectance of the gain element for light incident from the external cavity at low power. This unsaturated reflectance was compared to its target function, which was constant at a specified value larger than unity over a wide, prescribed wavelength range. The fabricated gain element was used in a linear OP-SDL with a rotatable intra-cavity birefringent filter for wavelength tuning. The design principles for achieving wide tunability were experimentally validated by the strong agreement between measurements and simulations of the spectral threshold pump intensity. Furthermore, tuning experiments at high pump powers were performed showing that the lasing wavelength could be tuned from 967 nm to 1010 nm with a maximum output power of 2.6 W.

Mid-infrared semiconductor laser are highly attractive sources for environmental monitoring since the spectral fingerprints of many environmentally important gases are located in the 2-3.3 μm wavelength regime accessible by gallium-antimonide technology. Here an electrically-pumped vertical-external-cavity surface-emitting laser (EP-VECSEL) was realized at 2.34 μm wavelength, using a gain mirror based on the GaSb material system. The gain mirror was grown by molecular beam epitaxy on an n-type GaSb substrate and it included a distributed Bragg reflector made of 24-pairs of AlAsSb/GaSb layers, and a gain region with 5 GaInAsSb quantum wells placed in a 3-λ thick micro-cavity. A structured buried tunnel junction (BTJ) with subsequent overgrowth was used in order to obtain efficient current confinement, reduced optical losses and increased electrical conductivity. Different components were tested with aperture sizes varying from 30 μm to 90 μm. Pulsed lasing was obtained with all tested components at 15 °C mount temperature. We obtained a maximum peak power of 1.5 mW at wavelength of 2.34 μm.

We demonstrate a dilute nitride (GaInAsN) based gain mirror capable of meeting the wavelength and linewidth requirements for laser guide stars. The mirror was grown by molecular beam epitaxy on a GaAs(100) substrate. The heat generated during laser operation was extracted from the active region with a wedged intracavity CVD diamond. An intracavity birefringent filter was employed for wavelength selection and a YAG etalon for linewidth narrowing. The laser radiation was intra-cavity frequency doubled to achieve emission at 589 nm. The frequency-doubled semiconductor disk laser emitted a narrow linewidth beam (~20 MHz) at 589 nm. In a free-running mode, the laser emitted more than 6W of yellow-orange light with a maximum conversion efficiency of 15.5%.

We report on the development of monolithic two-section dilute nitride passively mode-locked ridge-waveguide lasers. The dilute nitride material system can cover a wide wavelength range from 1.2 μm to 1.6 μm, while enabling fabrication on low-cost GaAs substrates. The laser structure comprised 3 GaInNAs quantum wells embedded within GaAs waveguide and AlGaAs claddings. To achieve mode-locking at 40 GHz repetition rate the laser chips consisted of a 950 μm long gain section and a 90 μm long reverse biased absorber section with a ridge width of 3.5 μm. The mode-locked laser output exceeded 3 mW per as-cleaved facet with 80 mA current in the gain region and a reverse voltage of 3.8 V applied to the saturable absorber. The corresponding pulse width was 3.4 ps. To study the effect of increasing the number of N-related recombination traps present in the proximity of the quantum wells, we have compared the performance of lasers employing GaAsN or GaAs as quantum well barriers. Time-resolved photoluminescence measurements revealed that the material comprising GaAsN barriers exhibited a photoluminescence lifetime of 12 ps with a reverse bias of 5 V. For similar reverse bias, the photoluminescence lifetime for material comprising GaAs barriers was 108 ps.

Monolithic semiconductor mode-locked lasers (MLLs) are rising considerable interest for such diverse applications as very high speed optical time division multiplexing sources (40-160 GHz), all-optical signal processing, and low noise sampling for signal monitoring of optical networks. In a large number of these applications, MLLs may be subjected to optical feedback generated by unwanted reflections in optical systems which may greatly degrade laser performance. A number of experimental studies have been performed to evaluate the sensitivity of MLLs to optical feedback showing an increase of phase noise [1-5]. Quantum-dash (Qdash) based Fabry Perot lasers have been shown to exhibit an improved tolerance to feedback [6]. In this work, optical feedback tolerance is investigated for a monolithic quantum-dash-based passive mode-locked laser emitting at 1.58 μm. The two-section device generates ~5 ps pulses at a repetition rate of 17 GHz. The onset of the coherence collapse (CC) regime is experimentally determined by measuring the broadening of the longitudinal modes in the optical spectrum. Depending on bias condition, the CC regime is reached for values of feedback ranging from -35 dB to -29 dB at which emitted pulses were slighly broadened. The radio-frequency (RF) linewidth was simultaneously assessed and a drastic reduction of the RF linewidth with increasing feedback strength is evidenced. This indicates a reduction of the phase noise, thus implying a low "high frequency" timing jitter. We in particular observed an RF linewidth narrowing down to a value of less than 1 kHz under optical feedback.

This paper reports the fabrication and the characterisation of a 10 GHz two-section passively mode-locked quantum dash laser emitting at 1.59 μm. The potential of the device's mode-locking is investigated through an analytical model taking into account both the material parameters and the laser geometry. Results show that the combination of a small absorbing section coupled to a high absorption coefficient can lead to an efficient mode-locking. Characterisation shows mode-locking operation though output pulses are found to be strongly chirped. Noise measurements demonstrate that the single side band phase noise does not exceed -80 dBc/Hz at 100 kHz offset leading to an average timing jitter as low as 800 fs. As compared to single QW lasers these results constitute a significant improvement and are of first importance for applications in optical telecommunications.

High-brightness tapered diode lasers (TPLs) are an ideal high-luminance light source for display applications such as pocket projectors, laser TVs, laser shows, and projectors for virtual reality simulators, because TPLs have a high optical output power in the visible range with a nearly diffraction-limited beam. We present results of high-power TPLs emitting between 630 nm and 660 nm. The diode lasers have a nearly diffraction-limited beam quality (M² _1/e2 < 3) and a maximum output power up to 1.55 W. A luminous flux of 84 lm and a luminance of 47 Tcd/m² was achieved with a TPL emitting 0.70 W near 640 nm. Lifetime tests show an operation > 5000 h at a power level of 200 mW.

An interesting aspect of semiconductor quantum dot lasers is their potential for fast dynamical response. Since carrier relaxation is slowed down for discrete energy levels, it is generally agreed that nonequilibrium effects will have strong influence on dynamical behavior in quantum dot lasers. In this paper, we show that, furthermore, many-body effects should be taken into account. The reason is that the interplay of bandgap renormalization, population-hole burning and inhomogeneous broadening is crucial for understanding quantum dot laser dynamics. For example, when operating with a microcavity, the interplay gives rise to modifications of relaxation oscillation behavior that is beyond what can be described by the usual 2-variable rate equation treatment. The theory used in the simulations is based on a semiclassical approach, where the laser field and active medium are described by the Maxwell-semiconductor-Bloch equations. Many-body Coulomb effects are described in the screened Hartree-Fock approximation. Carrier-carrier and carrier-phonon collisions are treated within the effective relaxation rate approximation, with the effective rates estimated from a quantum mechanical approach. Current injection and carrier capture, details of the electronic structure, as well as influences of spectral-hole burning and state-filling in an inhomogeneously broadened quantum dot distribution are taken into account. This theory provides a microscopically consistent description of a quantum dot laser and allows one to perform parametric studies on time scales ranging from subpicosecond to nanoseconds.

Quantum well (QW) VCSELs have a tendency to switch their polarization from one linearly polarized (LP) mode to the orthogonal one when changing the operation conditions. As polarization properties of VCSELs are governed by anisotropies, namely stress-induced birefringence and dichroism, the inherent anisotropy of quantum dots (QDs) is expected to influence the polarization properties of QD VCSELs. In this paper we summarize our experimental results on polarization properties of QD VCSELs with the main focus on polarization switching phenomena. Close to threshold the laser emits linearly polarized light which changes to elliptically polarized (EP) at some current. The main axes of these states are not aligned and the angle between them increases with current. As the current is still increased polarization switching accompanied by polarization mode hopping occurs. Distinctive feature of the observed switching is that the two EP states between which switching occurs are nonorthogonal. The angle between their major exes is 40 deg. Polarization mode hopping has been characterized in terms of the dwell time and the current-dependence of this factor examined. Apparently, the dwell time decreases when the pump current is increased which differs from what has been published for QW VCSELs. The average dwell time is 20 ns. Similarly to QW VCSELs the distribution of the dwell time is exponential. The statistics is the same for the two EP states and such symmetric switching is maintained in the whole range of currents at which the light is elliptically polarized. Large-signal modulation experiments show that the frequency at which polarization switching disappears is about 100 MHz. This indicates that the switching is of thermal origin.

We present a numerical model based on a time-domain travelling-wave approach to describe pulse propagation in InAs Quantum-Dot (QD) based Semiconductor Optical Amplifiers (SOA) and Saturable Absorbers (SA). The one-dimensional field propagation equation is solved in the time domain, in the slowly varying envelope approximation and it is coupled to a set of multi-population rate-equations modeling carrier dynamics in the QD layers in each longitudinal section of the waveguide. The optical response of the QD active medium is introduced in the field equation via a proper polarization term described as a set of infinite impulse response numerical filters. The inhomogeneous broadening of the density of states of the QD system induced by the QD size dispersion is properly taken into account. The influence of a static electric field on carrier dynamics in a reversely biased SA is described in the rate equations via bias dependent thermionic escape rates and tunneling processes. Absorption dynamics in a QD SA shows an initial ultrafast, bias independent recovery, followed by a slower recovery strongly dependent on the applied reverse bias. The QD SOA shows instead a dominant ultrafast gain recovery on a subpicosecond time scale at both QD Ground-States (GS) and first Excited-States (ES₁) wavelengths. Direct capture/escape processes between quantum well states and deeply confined QD states slightly influence the gain and absorption dynamics.

In this paper we report the design, fabrication, simulation and characterization of a novel discretely tunable laser based on filtered feedback. This Integrated Filtered-Feedback Tunable Laser (IFF-TL) device combines a simple and robust switching algorithm with good wavelength stability. It consists of a Fabry-Perot laser with deeply-etched broadband DBR mirrors. Single mode operation is achieved by using feedback from an integrated filter. This filter contains an AWG wavelength router and an SOA gate array. A rate equation model predicts that a properly designed device can switch within 1 ns, while characterization measurements show a value of only 4 ns. The fast switching and reduced control complexity makes the device very promising for various advanced applications in optical telecommunication networks.

We simulated the cold-cavity optical modes of coupled defect cavities in photonic crystal (PhC) vertical-cavity surface-emitting lasers (VCSELs). Holes were etched into the top distributed Bragg reflector of the COST benchmark structure in hexagonal pattern, leaving 2×1 or 2×2 positions intact. A lattice constant of 4 μm was selected, the hole diameter-to-lattice-constant ratio was varied from 0.5 to 0.7 outside the defect region and from 0.15 to 0.7 between the cavities. We used finite volume method to discretize the scalar Helmholtz equation, and finite element method to solve the vectorial Helmholtz equation, both in three dimensions. Prism elements were selected that fit the complicated contours of the PhC-VCSEL. In-phase and out-of-phase couplings were specified with different symmetry boundary conditions. The complex eigenvalues and optical field distributions were obtained with an in-house developed iterative algorithm. The real part of the eigenvalue determined the wavelength, its imaginary part was proportional to the cold-cavity modal loss. In-phase and out-of-phase coupled modes possessed almost equal properties when all holes had relatively large diameters, indicating uncoupled behavior. For a narrower hole between the defect cavities, the in-phase coupled mode exhibited slightly larger mode area than its out-of-phase counterpart due to its extending tails, but also showed considerably larger optical loss. This predicted out-of-phase operation. If one etched very small holes into the coupling region of the 2×2 PhC-VCSEL array, an additional lobe appeared between the holes, which resulted in enhanced overlap with the gain region. This confirmed in-phase operation.

A new 5-pin transistor outline (TO-Can) header for conventional coaxial laser package has been proposed and demonstrated by using a three-dimensional full-wave electromagnetic simulation tool. The applicability of the simulation tool was verified by a measurement result of a conventional TO-56 header. By adopting a two-session feed-through via and a bent feed-lead, this TO-Can header has the optimal impedance for high-speed modulation. The reflection loss can be controlled beneath -10-dB before 15-GHz with a 50-Ω termination. The 3-dB modulated bandwidth with a load impedance of 5-Ω and 50-Ω is over 23-GHz and 37-GHz, respectively. This TO-Can header provides a low-cost coaxial laser package solution with widely load impedances from 5-Ω to 50-Ω and may apply in the emerging 100-Gigabits Ethernet (100GbE) and next generation Fiber Channel (20GFC) applications.

In this paper we numerically demonstrate that an optical memory can be based on a two-mode laser diode with optical feedback and injection in the short external cavity regime. For modelling this system we use a two-mode extension of the Lang-Kobayashi rate equations with gain saturation and optical injection. The parameters chosen are consistent with the simultaneous oscillation of the two modes in the free running laser, which is possible for frequency spacings greater than approximately 500 GHz at optical frequencies around 200 THz. For certain values of the system parameters, we have found a hysteresis loop between single-mode equilibrium states for increasing and decreasing feedback strength. Our simulations show that injected optical pulses can switch the system between single mode equilibrium states when the feedback parameters are fixed in this bistable region, demonstrating the function of the optical memory. This system has attractive features such as the absence of a holding beam and the symmetry between the two states of the memory element. These properties along with the external cavity length of 1 cm make the system an interesting candidate for optical integration.

This research investigated the feasibility of applying beam-profile adapted optical feedback to generate single high-order transverse modes in a commercial multi-transverse mode vertical-cavity surface-emitting laser (VCSEL). The beam-profile adaption was achieved by launching the multi-transverse-mode beam profile of the solitary VCSEL into a single-mode fiber. At the fiber's exit, a quasi-Gaussian beam profile was easily obtained. Afterward, the beam was passed through a spatial light modulator (SLM), and was then fed back into the laser's cavity. The SLM was designed to have the intensity pattern of a designated transverse mode. Accordingly, the beam profile of the feedback beam was adapted to be the pattern of a single transverse mode. Conducting by the feedback beam, the VCSEL would lase the designated single transverse mode with a side-mode suppression ratio about 10 dB. More experimental details will be presented. These results will help to expand the application of VCSELs.

We present our evaluation of a compact laser system made of a 795 nm VCSEL locked to the Rubidium absorption line of a micro-fabricated absorption cell. The spectrum of the VCSEL was characterised, including its RIN, FM noise and line-width. We optimised the signal-to-noise ratio and determined the frequency shifts versus the cell temperature and the incident optical power. The frequency stability of the laser (Allan deviation) was measured using a high-resolution wavemeter and an ECDL-based reference. Our results show that a fractional instability of ≤ 10^-9 may be reached at any timescale between 1 and 100'000 s. The MEMS cell was realised by dispensing the Rubidium in a glass-Silicon preform which was then, sealed by anodic bonding. The overall thickness of the reference cell is 1.5 mm. No buffer gas was added. The potential applications of this compact and low-consumption system range from optical interferometers to basic laser spectroscopy. It is particularly attractive for mobile and space instruments where stable and accurate wavelength references are needed.

High power diode lasers are used in a large number of applications. A limiting factor for more widespread use of broad area lasers is the poor beam quality. Gain guided tapered diode lasers are ideal candidates for industrial applications that demands watt level output power with good beam quality. By adapting a bar geometry, the output power could be scaled even up to several tens of watts. Unfortunately, the high divergence which is a characteristic feature of the bar geometry could lead to a degradation of the overall beam quality of the laser bar. However, spectral beam combining is an effective solution for preserving the beam quality of the bar in the range of that of a single emitter and at the same time, enabling the power scaling. We report spectral beam combining applied to a 12 emitter tapered laser bar at 980 nm. The external cavity has been designed for a wavelength separation of 4.0 nm between the emitters. An output power of 9 W has been achieved at an operating current of 30 A. The combined beam had an M² value (1/e²) of 5.3 along the slow axis which is comparable to that of a single tapered emitter on the laser bar. The overall beam combining efficiency was measured to be 63%. The output spectrum of the individual emitters was narrowed considerably. In the free running mode, the individual emitters displayed a broad spectrum of the order of 0.5-1.0 nm while the spectral width has been reduced to 30-100 pm in the spectral beam combining mode.

In this work we report on an experimental investigation of the bistability found in 1550 nm multitransverse-mode VCSELs subject to orthogonal optical injection. The VCSEL emits in two transverse modes that are linearly polarized in a direction referred as parallel. We study the dependence of the bistable behaviour on the detuning between the frequency of the externally injected signal and the frequency of the subsidiary orthogonal linear polarization of the fundamental mode of the VCSEL. Different qualitative behaviors of the power of each polarized transverse mode versus the optically injected power appear depending on the value of the frequency detuning. Bistable regions are very narrow for positive and small negative values of the frequency detuning. However very wide hysteresis cycles are obtained for large and negative values of the frequency detuning. Bistability is found for both the fundamental and the high-order transverse mode. The shape of the hysteresis cycle depends on the transverse mode under consideration. The power of the parallel polarized fundamental transverse mode decreases gradually as the injected power is increased. However the behaviour of the parallel polarized high-order transverse mode is different because its power remains constant as the optical injected power is increased until it suddenly drops to low levels. This kind of behaviour is of interest for obtaining good quality all-optical inversion and all-optical regeneration.

Vertical cavity surface emitting lasers (VCSELs) are low cost and reliable light sources for high-speed local area and storage area network (LAN/SAN) optical fiber data communication systems and all other short-reach high-speed data transfer applications. The intrinsic limitations of copper-based electrical links at data rates exceeding 10 Gbit/s leads to a progressive movement wherein optical communication links replace traditional short-reach (300 m or shorter) copper interconnects. The wavelength of 850 nm is the standard for LAN/SAN applications as well as for several other evolving short-reach application areas including Fibre Channel, InfiniBand, Universal Serial Bus (optical USB), and active optical cables. Here we present our recent results on 850 nm oxide-confined VCSELs operating at data bit rates up to 40 Gbit/s at low current densities of ~10 kA/cm² ensuring device reliability and long-term stability based on conventional industry certification specifications. The relaxation resonance frequencies, damping factors, and parasitic cut-off frequencies are determined for VCSELs with oxide-confined apertures of various diameters. At the highest optical modulation rates the VCSELs' high speed operation is limited by parasitic cut-off frequencies of 24-28 GHz. We believe that by further reducing device parasitics we will produce current modulated VCSELs with optical modulation bandwidths larger than 30 GHz and data bit rates beyond 40 Gbit/s.

We report the design, fabrication and characterization of oxide-confined large-area rectangular-shaped VCSELs that emit a single higher-order transverse mode. The mode selection mechanism is based on an inverted surface relief. In this method, extra losses are induced by a quarter-wavelength-thick antiphase layer, into which a multi-spot pattern is etched in a single step. The main parameters that control the selected mode, such as the threshold gain and the three-dimensional confinement factor, are calculated as a function of the active aperture dimensions for various structures, patterns, and aspect ratios, aiming to achieve single-higher-order transverse mode emission. Based on the design rules, 850 nm wavelength top-emitting GaAs/AlGaAs VCSELs have been fabricated and characterized. Devices with an aperture area of about 6 × 68 μm² show high output powers of 12 mW in the (8, 1) order mode and differential resistances of only 18 ohms. In addition, the asymmetric transverse cavity can be used to achieve oscillation on a single polarization. Optical manipulation of micro-particles is a promising biophotonic application area for the investigated VCSELs. In an optical tweezers setup, a multi-spot VCSEL is positioned under an angle of about 25 degrees with respect to the fluidic flow direction. Lateral all-optical deflection of flowing 10 μm diameter polystyrene particles is achieved, which is of particular interest for non-mechanical sorting in a microfluidic chip. With the multi-spot VCSEL, the distance between the intensity spots is 9 μm, which cannot be easily achieved with conventional linear VCSEL arrays. Trapping and stacking of polystyrene microspheres are also shown.

We theoretically investigate optical injection in semiconductor ring lasers. Starting from a rate-equation model for semiconductor ring lasers, we use numerical simulations and a bifurcation analysis to reveal all the relevant dynamical regimes that will unfold for different parameter values. Our numerical simulations reproduced the saddle-node and Hopf bifurcation observed in other optically injected laser systems, which typically yield the boundaries of the parameter region in which stable locking can occur. Nevertheless, the bifurcation diagram of the optically injected semiconductor ring laser shows differences with the ones of other semiconductor lasers. For low injection power, we not only observe the regular saddle-node locking bifurcation, we also reveal the presence of an additional family of saddle-node bifurcations and a new Hopf bifurcation. These new bifurcations lead to the coexistence of two injection-locked states in two separate parameter regions and a parameter region is revealed in which a frequency-locked limit cycle coexists with an injection-locked solution, providing an additional route to stable locking. Finally, a chaotic regime that extends to low values of the detuning and injection power is revealed.

We discuss how the nonmodal emission regime's farfield of a broad-area vertical-cavity surface-emitting laser (BAVCSEL) can be used for low-speckle laser projection. More specifically we investigate how the farfield of a BA-VCSEL in its nonmodal emission regime can be used for low-speckle laser projection. A microlens beam homogenizer is used to exploit the low spatial coherence of the VCSEL. Speckle contrast values as low as 2.5% are measured without using any additional or mechanically moving components to destroy the coherence of the laser beam. We explore and explain the effect on the speckle contrast of the beam's size on the homogenizer. We successfully modeled the speckle contrast reduction, taking into account all contributing speckle reducing factors.

A high-power single-mode 1.3-μm InGaAs/GaAs vertical-cavity surface-emitting laser (VCSEL) structure employing a novel concept of engineering the optical mode profile to match the gain profile is suggested and demonstrated experimentally and theoretically. In contrast to various singlemode VCSEL approaches reported in the literature so far, based on selective loss or anti-resonant effects to suppress higher order modes, it is due to a novel design to increase the active region size while maintaining single mode emission. The shape of the fundamental mode profile is engineered to be similar to the gain profile which resembles a doughnut shape especially in intra-cavity contacted devices. In this way, the fundamental mode with the best fit to the gain profile can reach the lasing condition earliest and consume all the optical gain, leading to a suppression of higher order modes. Notably, despite this engineered shape of the mode profile, the far field shape remains close to Gaussian. The mode shaping can be achieved by introducing a shallow intracavity patterning before depositing the top mirror. Fabricated device structures consist of a A-Si/SiN/SiO₂ top mirror, modulation-doped current spreading layers, re-grown current confinement layers, three InGaAs/GaAs quantum wells, and a GaAs/AlGaAs bottom mirror. Single mode operation is demonstrated even for devices with active region as large as 10μm.

We analyze the influence of the excited states (ES) on the dynamics of optically injected quantum dot lasers. In our model carriers from the wetting layer are first being captured into the excited state and then relax to the ground state. Our results indicate that the dynamics of optically injected QD lasers are driven by the relaxation time in the sense that it scales the regions where the laser exhibits distinct behaviors. It also influences the size of the locking region. The capture time has minor effect and influences mainly static characteristics. Bifurcation maps are studied with the main focus on self-pulsations. In particular our results show that the dynamics of self-pulsations is consistent with experimental observations of excitable dynamics. To utilize the self-pulsations we propose and investigate properties and limitation of the system used for all-optical signal processing. In our approach the slave laser is switched by the information signal acting as a master laser between the locking region and the region of self-pulsations. The maximum bit rate of such a system has been estimated to be 0.5 GHz. This value can be improved to 1 GHz by applying correction to the detection algorithm. The correction reflects the nature of self-pulsations and is calculated from the distribution of the time the system needs to fire a pulse.

We study the synchronization behavior of Stuart-Landau oscillators coupled with delay, using analytical and numerical methods. We compare the dynamics of one oscillator with delayed feedback, two mutually oscillators coupled with delay, and two delay-coupled elements with feedback. Taking only the phase dynamics into account, no chaotic dynamics has been observed. Moreover, the stability of the symmetric (identical synchronization) solution is the same in each of the three studied networks of delay-coupled elements. When allowing variable oscillation amplitude, the delay can induce amplitude instabilities. We provide analytical proof that, in case of two mutually coupled elements, the onset of an amplitude instability is accompanied by a symmetry breaking, leading to the in lasers observed leader-laggard behavior in the chaotic regime. Adding self-feedback (with the same strength and delay as the coupling), stabilizes the system in transverse direction.

We have performed an experimental investigation of the RIN spectra of multimode 1550 nm VCSELs. Several types of multi-transverse mode VCSELs have been considered. The first one emits in two transverse modes for large values of the bias current. Both modes are linearly polarized and have parallel polarizations. Two resonance peaks appear in the noise spectra of the individual modes and total power of the VCSEL in agreement with previous theoretical studies (A. Valle et al, IEEE J. Quantum Electron, vol. 40, 597, 2004). We have measured the frequencies corresponding to both peaks as a function of the bias current. We have obtained a similar dependence to the one found in the previous work. The second VCSEL type corresponds to a laser emitting at three different transverse modes for large values of the bias current. Similar behaviors are found while the bias current is small. Emission in three transverse modes with different polarizations is accompanied by the appearance of additional peaks in the noise spectra. It is suggested that the VCSEL polarization plays an important role in determining the multi-peaked structure of noise spectra. That is confirmed by measuring with another two-transverse mode VCSEL showing polarization instabilities in both transverse modes. It is shown that large values of the bias current applied to this VCSEL result in a complex dynamics characterized by the appearance of many additional peaks in the noise spectra.

Optical chaos-based cryptosystems hide an information-bearing message within the chaotic dynamics of a laser system. On-off phase-shift keying (OOPSK) is considered to be a particularly efficient encryption technique. It is based on the modulation of the feedback phase of a chaotic external-cavity emitter laser at the rhythm of a digital message. At the receiving end, message values are decrypted by observing the synchronization and de-synchronization of an external-cavity receiver which has a constant feedback phase. This cryptosystem is popular because so far it has been thought to be impossible to find the message by analyzing the chaotic optical field transmitted from the emitter to the receiver laser, thus, it is hitherto thought, providing high security. We demonstrate that the phase modulation produces a displacement of the chaotic attractor which is detectable by analyzing low-dimensional projections or sections of the high-dimensional attractor. This leads to the successful decryption of the message value based on an analysis of the chaotic optical field sent to the receiver only. We show that the bit-error-rate (BER) of the decrypted message varies with the modulation depth and speed. Though small depths and large bit rates lead to an increase of the BER, we find it possible to extract the message for most operating conditions of an on/off phase- shift keying-based cryptosystem.

We present the first demonstration of the generation of single sideband (SSB) modulation using a monolithic integrated electro-absorption modulated laser (EML) device. Suppression of upper or lower sidebands is observed under synchronous dual analog narrow band driving of the laser and the modulator sections. The 10 GHz carrier can transport digital format data for a wide variety of Radio-over-Fiber (RoF) transmission systems. A 50 MBaud/s transmission of a 16-QAM signal has been achieved over 150 km of Standard Single Mode (SMF) fiber. Constellations, eye diagrams and error vector magnitude (EVM) measurements are presented, all of which are temperature independent up to 45°C. This demonstration of SSB modulation capability, which allows for signal transmission with a high spectral efficiency, free of side-band beating and with a uniform signal power over the entire length of the optical fiber, makes the device ideal for use in both optical metropolitan and optical access networks. Our experimental results establish the dual-EML SSB transmitter as a serious candidate for optical-wireless network convergence and future OFDM systems.

Semiconductor Ring Lasers (SRLs) are a novel class of semiconductor lasers whose active cavity is characterized by a circular geometry. SRLs have attracted attention due to the possibility of monolithical integration of thousands of them on the same chip in a cheap and reliable way. SRLs are interesting for applications that rely on the presence of two counter-propagating modes inside the optical cavity. For instance, fully symmetric coupled SRLs have been proposed as candidates for the realisation of small and fast all-optical memories. At the same time, a wealth of nonlinear and stochastic dynamics have been predicted and observed in symmetric SRLs which is a consequence of the underlying Z2-symmetry of the device. However, unavoidable fabrication defects, material roughness and chip-cleaving break the device symmetry in an uncontrolled and unpredictable way, which may result in a deterioration of the device's performance in applications such as all-optical signal-processing. Despite their importance, the effects of symmetry breaking in SRLs remain unaddressed. In this contribution we investigate theoretically and experimentally the stochastic dynamics of SRLs with weakly broken Z2-symmetry . We show how the symmetry of an SRL can be experimentally manipulated using the reflection from a cleaved facet of a multi-mode optical fibre and a control electrode on the bus waveguide. The experiments are performed on an InP-based multi-quantum well SRL operating in single-longitudinal mode regime. The power at the CCW output is collected using a fast photodiode connected to an oscilloscope with a sampling rate of 4.0 ns. For a not-too-weak symmetry breaking, we reveal that SRLs become excitable and therefore can emit large, deterministic power bursts as a response to stochastic fluctuations. The origin of excitability is explained by investigating the topology of the invariant manifolds of an asymptotic two-dimensional phase space model with broken Z2-invariance. The results of the experiments confirm the prediction of the theory.

We present both an experimental and theoretical investigation of multistable states in a single-longitudinal mode and single transverse mode semiconductor ring laser (SRL). Our experiments have been performed on an InP-based multiquantum-well SRL with a racetrack geometry and a free-spectral-range of 53.6 Ghz. The power emitted from the chip is collected with a multimode fiber and detected with a 2.4 GHz photodiode connected to an oscilloscope. We show how the operation of the device can be steered to either monostable, bistable or multistable dynamical regimes in a controlled way. The diverse multistable dynamical regimes are shown to be organized in well reproducible sequences [Gelens et al., Phys. Rev. Lett. 102, 193904 (2009)]. These sequences are demonstrated to match the bifurcation diagrams of an asymptotic two-dimensional Z₂-symmetric model for SRLs. Apart from predicting the different measured multistable time series, we demonstrate how the stochastic transitions between multistable states take place by analyzing the phase space in this model.

Performances of scanning wavelength systems are limited by several factors like the sweeping range, the mode-hop-free tuning of the wavelength and the nonlinearities in the sweeping speed. Nonlinearities are probably the last parameter to control to get the least performances. In our absolute distance interferometer (ADI), we have observed that the processing technique of the fringes in case of a double target system is very sensitive to the type of nonlinearities and the final resolution of the ADI depends strongly on their shape. Although the ideal sweeping speed should be perfectly linear, we have observed that even in the presence of strong sinusoidal nonlinearities in the sweeping speed, unexpected good results were obtained and were explained by the fact that these nonlinearities act like some white noise whose contribution converges to zero as the number of samples of the processed signal increases. In this paper we focus on the symmetry of the spectrum, another consequence of these nonlinearities. We show how it is possible to manipulate the spectrum by changing the sweeping speed. Results of simulations as well as experimental measurements are presented.

A non-destructive method of reliability prediction for PN junction microelectronic devices is presented. Transport and noise characteristic of forward biased semiconductor lasers diodes GaSb based VCSE (Vertical Cavity Surface Emitting) lasers were prepared by Molecular Beam Epitaxy were measured in order to evaluate the new MBE technology.

In this paper we present our recent works on optical injection of Fabry-Perot laser diode for application in access networks. The injection-locked Fabry-Perot laser diode is used as low-cost colorless transmitters for high-speed optical access exploiting wavelength-division-multiplexing technology. The modification of main characteristics of Fabry-Perot laser such as spectral properties, noise and modulation is shown in injection-locking regime. The strong dependence of these properties onto injection parameters is also given. Finally, the operation of injection-locked Fabry-Perot laser diode in a wavelength-division-multiplexed optical access system using a novel multi-wavelength master source based on quantum-dash mode-locked laser is presented and its transmission performances at 2.5 Gb/s are reported.

Thanks to optimized growth techniques, a high density of uniformly sized InAs quantum dots (QD) can be grown on InP(113)B substrates. Low threshold currents obtained at 1.54 μm for broad area lasers are promising for the future. This paper is a review of the recent progress toward the understanding of electronic properties, carrier dynamics and device modelling in this system, taking into account materials and nanostructures properties. A first complete analysis of the carrier dynamics is done by combining time-resolved photoluminescence experiments and a dynamic three-level model, for the QD ground state (GS), the QD excited state (ES) and the wetting layer/barrier (WL). Auger coefficients for the intradot assisted relaxation are determined. GS saturation is also introduced. The observed double laser emission for a particular cavity length is explained by adding photon populations in the cavity with ES and GS resonant energies. Direct carrier injection from the WL to the GS related to the weak carrier confinement in the QD is evidenced. In a final step, this model is extended to QD GS and ES inhomogeneous broadening by adding multipopulation rate equations (MPREM). The model is now able to reproduce the spectral behavior in InAs-InP QD lasers. The almost continuous transition from the GS to the ES as a function of cavity length is then attributed to the large QD GS inhomogeneous broadening comparable to the GS-ES lasing energy difference. Gain compression and Auger effects on the GS transition are also be discussed.

The time evolution of the output of a semiconductor laser subject to optical feedback can exhibit high-dimensional chaotic fluctuations. In this contribution, our aim is to quantify the complexity of the chaotic time-trace generated by a semiconductor laser subject to delayed optical feedback. To that end, we discuss the properties of two recently introduced complexity measures based on information theory, namely the permutation entropy (PE) and the statistical complexity measure (SCM). The PE and SCM are defined as a functional of a symbolic probability distribution, evaluated using the Bandt-Pompe recipe to assign a probability distribution function to the time series generated by the chaotic system. In order to evaluate the performance of these novel complexity quantifiers, we compare them to a more standard chaos quantifier, namely the Kolmogorov-Sinai entropy. Here, we present numerical results showing that the statistical complexity and the permutation entropy, evaluated at the different time-scales involved in the chaotic regime of the laser subject to optical feedback, give valuable information about the complexity of the laser dynamics.

Self-sustained pulsations in the output of an InAs quantum dot laser diode in the MHz range are reported for the first time. The characteristics (shape, range and frequency) are presented for the free running laser and when optical feedback in the Littrow configuration is applied. The frequency resolved optical spectra reveal different envelope shifts between the two cases. This might be related to a change of phase-amplitude coupling across the gain maximum in agreement with the expectation for a two level system. The time scale and bifurcation scenario suggest that these are opto-thermal pulsation like those reported in quantum well amplifiers.