This PDF file contains the front matter associated with SPIE Proceedings Volume 9357, including the Title Page, Copyright information, Table of Contents, Introduction, Authors, and Conference Committee listing.

Chaotic Lidar systems (CLIDAR) are used for high-resolution ranging. They are based on the correlation of a chaotic signal waveform with the signal that is reflected back from the target. We report a novel CLIDAR system based on the autocorrelation of the signal obtained by the superposition of the chaotic signal waveform and the signal that is reflected from the target. A simplified set-up with just one detector is required in contrast to the two detectors used in standard CLIDAR systems. Our experimental results are obtained with a 1550-nm vertical-cavity surface-emitting laser (VCSEL) with chaotic dynamics due to optical feedback. Our CLIDAR system provides an autocorrelation function with several sharp minima. The position of the target is obtained from the location of those minima. A theoretical analysis of the CLIDAR system is also presented. A rate equation model for the polarization of a VCSEL subject to optical feedback is the basis for the simulation of the CLIDAR system. A comparison between our theoretical and experimental results is performed, resulting in a good agreement in the chaotic signal but in a different sign of the CLIDAR signal.

In recent years quantum dot lasers (QDLs) and optically injected QDLs in particular, have provided a new arena for the demonstration of many intriguing non-linear phenomena. We show here that slow optothermal relaxations may significantly affect the output dynamics in QDLs for both the free running and the external injection configurations. In particular, square-wave intensity drop-outs and pulsations can be obtained reminiscent of Fitzhugh-Nagumo excitable dynamics.

In actively modulated laser systems such as the time-lens source, quadratic temporal phase modulation was naturally considered as the “ideal” modulation. However, it is unknown that whether a quadratic temporal phase modulation (equivalently, a linear chirp) translates into a quadratic spectral phase modulation, which can be easily eliminated using compressors. Here we study this phase transfer both analytically and numerically. Our results indicate that non-quadratic spectral phase aberration arises even if the temporal phase modulation is quadratic. Consequently, there is observable difference between the compressed pulses with a flat spectral phase and with quadratic spectral phase compensation only. However, as quadratic temporal phase modulation increases, non-quadratic spectral phase modulation decreases, and pulse compression with quadratic spectral phase tends to that with a flat spectral phase.

In order to understand the response of conductive materials to high-frequency electrical or optical excitations, the interplay between carrier transport and electrodynamics must be captured. We present our recent work on developing EMC/FDTD/MD, a self-consistent coupled simulation of semiclassical carrier transport, described by ensemble Monte Carlo (EMC), with full-wave electrodynamics, described by the finite-difference time-domain (FDTD) technique and molecular dynamics (MD) for sub-grid-cell interactions. Examples of room-temperature terahertz-frequency transport simulation of doped silicon and back-gated graphene are shown.

We design and experimentally investigate various large-area gate-tunable terahertz plasmonic metasurfaces employing different types of graphene based structures, i.e. arrays of graphene ribbons, square-lattice graphene anti-dots and hexagonal-lattice graphene anti-dots. Distinct gate-tunable resonances in the terahertz frequency range arising from excitations of plasmonic resonance modes associated with different structures are observed in their transmission spectra. Carrier density dependent tuning of the resonance frequency exhibits excellent agreement with the theoretical prediction and the numerical simulation. The demonstrated graphene based terahertz plasmonic metasurfaces can be employed to realize more complex devices and functionalities such as tunable plasmonic waveguide and transformation optics.

A comparative study of the gain achievement is performed in a waveguide optical amplifier whose active layer is constituted by a silica matrix containing silicon nanograins acting as sensitizer of either neodymium ions (Nd³⁺) or erbium ions (Er³⁺). Due to the large difference between population levels characteristic times (ms) and finite-difference time step (10⁻¹⁷s), the conventional auxiliary differential equation and finite-difference time-domain (ADE-FDTD) method is not appropriate to treat such systems. Consequently, a new two loops algorithm based on ADE-FDTD method is presented in order to model this waveguide optical amplifier. We investigate the steady states regime of both rare earth ions and silicon nanograins levels populations as well as the electromagnetic field for different pumping powers ranging from 1 to 10⁴ mW/mm² . Furthermore, the three dimensional distribution of achievable gain per unit length has been estimated in this pumping range. The Nd³⁺ doped waveguide shows a higher gross gain per unit length at 1064 nm (up to 30 dB/cm^-1) than the one with Er³⁺ doped active layer at 1532 nm (up to 2 dB/cm^-1). Considering the experimental background losses found on those waveguides we demonstrate that a significant positive net gain can only be achieved with the Nd³⁺ doped waveguide. The developed algorithm is stable and applicable to optical gain materials with emitters having a wide range of characteristic lifetimes.

We present a detailed analysis of wave function localization effects in In_xGa_1−xN alloys and quantum wells. Our work is based on density functional theory to analyze the impact of isolated and clustered In atoms on the wave function localization characteristics in In_xGa_1−xN alloys. We address the electronic structure of In_0.25Ga_0.25N/GaN quantum wells by means of an atomistic tight-binding model. Random alloy fluctuations in the quantum well region and well-width fluctuations are explicitly taken into account. The tight-binding model includes strain and built-in field fluctuations arising from the random In distribution. Our density functional theory study reveals increasing hole wave function localization effects when an increasing number of In atoms share the same N atom. We find that these effects are less pronounced for the electrons. Our tight-binding analysis of In_0.25Ga_0.27N/GaN quantum wells also reflects this behavior, revealing strong hole localization effects arising from the random In atom distribution. We also show that the excited hole states are strongly localized over an energy range of approximately 50 meV from the top of the valence band. For the quantum wells considered here we observe that well-width fluctuations lead to electron wave function localization effects.

Incorporation of N into GaInAs results in N-localized-states close to the conduction band minimum. Such strong alloy band edge N-localized-states can locally capture carriers, thus lasing directly occurs from them, leading to dualwavelength emission.

A one-dimensional (1D) collisional relativistic particle-in-cell (PIC) code with ionization processes has been developed to investigate the key semiconductor manufacturing device, i.e., the extreme ultraviolet (EUV) light source from laserproduced plasmas (LPP). Unlike hydrodynamic approach, the kinetic model describes laser heating, energy transport and ultrafast electron dynamics with least approximations. The two major numerical effects of PIC simulations, i.e., numerical self-heating and numerical thermalization, are also studied and mitigated in the collisional PIC model. The integrated numerical model is achieved by simulating the dense plasma using collisional PIC model and estimating EUV emission and mean opacities according to the respective weighted oscillator strengths of tin ions with charged states varying from 5+ to 13+.

We address the behavior of mid-infrared localized plasmon resonances in elongated germanium antennas integrated on silicon substrates. Calculations based on Mie theory and on the experimentally retrieved dielectric constant allow us to study the tunability and the figures of merit of plasmon resonances in heavily-doped germanium and to preliminarily compare them with those of the most established plasmonic material, gold.

The absorption and reflection characteristics of multilayered nanoplasmonic gratings with sub wavelength sizes are analyzed in details by using an efficient finite element method. The multilayered structures are composed by several layers of nanoparticles of metals such as Silver, Gold and Aluminum embedded in dielectric such as amorphous silicon over a metallic substrate. The propagations characteristics for several geometrical configurations are obtained and a broadband reflection or absorption covering the near infrared wavelengths has been observed. The proposed nanoplasmonic structures have a great potential for applications in photovoltaic cells or polarizers by improving their reflection or absorption efficiency. Peaks of reflection or absorption larger than 80% were obtained and their performance over the near infrared can be improved by adequately tuning their geometrical parameters, the refractive index and thickness of the layers as well as the nanoparticles shape and size.

In recent years, experimental work has shown that significant luminescence enhancement can be obtained from quantum-well (QW) light-emitting diodes (LEDs) by using metallic grating, which diffracts efficiently optical modes and resonances trapped in these structures and converts surface plasmon (SP) modes into radiative modes. We employ a powerful simulation tool to provide a deep insight into the physics of plasmonic enhancement and present guidelines on how to optimize light-extraction in III-nitride LED structures incorporating an emitting InGaN QW located in the vicinity of a grated silver surface. The model uses first-principle theory, coupling the dyadic Green’s function formalism for solving Maxwell’s equations to fluctuational electrodynamics, and employs a recursive and transparent solution method allowing the fields to be written in a closed form. We demonstrate the significant effect of the type of the periodic grating and layer structure on light-extraction efficiency by simulating various structures with different grating shapes and dimensions. Careful optimization of the grating features shows that the maximum enhancement can reach a factor of around 8 as compared to the flat semiconductor structure and that the plasmonic losses can be significantly reduced.

We study InGaAs QD laser operating simultaneously at ground (GS) and excited (ES) states under 30ns pulsed-pumping and distinguish three regimes of operation depending on the pump current and the carrier relaxation pathways. An increased current leads to an increase in ES intensity and to a decrease in GS intensity (or saturation) for low pump range, as typical for the cascade-like pathway. Both the GS and ES intensities are steadily increased for high current ranges, which prove the dominance of the direct capture pathway. The relaxation oscillations are not pronounced for these ranges. For the mediate currents, the interplay between the both pathways leads to the damped large amplitude relaxation oscillations with significant deviation of the relaxation oscillation frequency from the initial value during the pulse.

This work theoretically studies the impacts of the inhomogeneous broadening on the modulation dynamics of quantum dot lasers using a multi-population rate equation model. The modulation dynamics shows two distinct regimes depending on the energy separation between the GS and the ES. For broadenings smaller than the GS-ES separation, the K-factor increases while the damping factor offset, the differential gain and the gain compression factor decrease with the inhomogeneous broadening. For broadenings larger than the GS-ES separation, the damping factor offset keeps almost constant while the K-factor, the differential gain and the gain compression factor increases with the inhomogeneous broadening.

The unique carrier processes in quantum dot lasers mean that lasing can be achieved at the ground state (GS) transition wavelength or at the excited state (ES) transmission wavelength or indeed simultaneously at both wavelengths. The details depend on the device characteristics and control parameters such as the pumping current and temperature. When the lasing is from the ES only one can induce all-optical switching between the two states via optical injection into the GS. The high damping of the relaxation oscillations in these devices allows for very fast switching times, with sub-nanosecond transitions easily obtained. Such ultrafast switching times are vastly superior to those obtained with conventional semiconductor lasers and make these devices very attractive for all-optical switching applications. The interplay of the two states leads to a new dynamic regime. Near the boundary of stable locking for the injected GS, deep GS intensity dropouts are observed. Further, each dropout in the GS coincides with a burst in the ES output.

We present a semiclassical theory of an optically pumped quantum dot phonon laser, based on a system of N quantum dots coupled to a high-Q acoustic phonon cavity. Based on a theory developed earlier [J. Kabuss, A. Carmele, and A. Knorr, Phys. Rev. B 88, 064305 (2013)], that was limited to the single emitter limit, a set of phonon laser equations is generalized to the many emitter regime and solved analytically. Similar to the optical laser it is possible to overcome the adverse effect of a phonon cavity loss with respect to entering the phonon laser regime by the number of quantum dots, that are coupled to the phonon resonator mode. Especially in the case of the proposed quantum dot phonon laser, which exhibits self-quenching, a shift of the laser threshold to lower pump powers and an inhibition of the self-quenching can be essential for entering the phonon lasing regime in the first place.

We propose a scheme to achieve cavity-assisted strong coupling between the internal degrees of a Rydberg superatom to a moving membrane in the single photon and phonon limit. Our set-up allows for efficient transfer between electronic excitation and single phonons by combining the collective enhancement effect of the superatom Rabi frequency with typical cavity-optomechanics schemes in the strong coupling limit.

We propose to use a time-delayed quantum-coherent feedback mechanism to increase and control the entanglement of photon pairs emitted by a quantum dot biexciton cascade. The quantum dot biexciton cascade is a well-known source of entangled photons on demand, however excitonic fine-structure splitting decreases the achievable polarization entanglement. We demonstrate that feedback can change the spectrum of the emitted photons in a way that the entanglement is either strongly increased or decreased, depending on the feedback time and phase. We analyze the dependence on parameters such as the delay time and the robustness of the proposed mechanism.

Ultralarge output apertures of semiconductor gain chips facilitate novel applications that require efficient feedback of the reflected laser light. Thick (10-30 μm) and ultrabroad (>1000 μm) waveguides are suitable for coherent coupling through both near-field of the neighboring stripes in a laser bar and by applying external cavities. As a result direct laser diodes may become suitable as high-power high-brightness coherent light sources. Passive cavity laser is based on the idea of placing the active media outside of the main waveguide, for example in the cladding layers attached to the waveguide, or, as in the case of the Tilted Wave Laser (TWL) in a thin waveguide coupled to the neighboring thick waveguide wherein most of the field intensity is localized in the broad waveguide. Multimode or a single vertical mode lasing is possible depending on the coupling efficiency. We demonstrate that 1060 nm GaAs/GaAlAs–based Tilted Wave Lasers (TWL) show wall-plug efficiency up to ~55% with the power concentrated in the two symmetric vertical beams having a full width at half maximum (FWHM) of 2 degrees each. Bars with pitch sizes in the range of 25–400 μm are studied and coherent operation of the bars is manifested with the lateral far field lobes as narrow as 0.1° FWHM. As the near field of such lasers in the vertical direction represents a strongly modulated highly periodic pattern of intensity maxima such lasers or laser arrays generate Bessel-type beams. These beams are focusable similar to the case of Gaussian beams. However, opposite to the Gaussian beams, such beams are self-healing and quasi non-divergent. Previously Bessel beams were generated using Gaussian beams in combination with an axicon lens or a Fresnel biprism. A new approach does not involve such complexity and a novel generation of laser diodes evolves.

Non-degenerate four-wave mixing effects are investigated in an injection-locked InAs/InP nanostructure Fabry-Perot laser. Locking a longitudinal mode at various wavelengths within the gain spectrum and using the locked mode as the pump for the wave mixing shows different levels of asymmetry between up- and down-conversion. Experiments reveal that the normalized conversion efficiency is less asymmetric when the pump is locked at wavelengths below that of the gain peak. The values of nonlinear conversion efficiencies are maintained above -60 dB for pump-probe frequency detunings up to 3.5 THz. The role of the linewidth enhancement factor on the asymmetry is discussed and the value of the nonlinear susceptibility is compared to similar InAs/InP nanostructure semiconductor optical amplifiers. From an end-user viewpoint, data transmission experiments have also confirmed the possibility to propagate up-converted signals over 100 km at a 5 Gb/s bit rate under an OOK modulation format.

We analyse the dynamical behaviour of a Fourier domain mode locked laser experimentally and theoretically. Heterodyne measurements of laser dynamics allows some insight into the frequency behaviour of the laser which coupled with theoretical arguments from previous work allow for a clear interpretation of the observations. Direct simulations using a delay differential equation model in full FDML mode display excellent agreement with the experimental results.

In this work we present a multiscale numerical simulation of solid-state Dye and Perovskite Solar Cells where the real morphology of the mesoporous active layer is taken into account. Band alignment and current densities are computed using the drift-diffusion model. In the case of Dye cells, a portion of the real interface is merged between two regions described using the effective medium approximation, casting light on the role of trapped states at the interface between TiO2 / Dye / hole transporting materials. A second case of study is the simulation of Perovskite Solar Cell where the performances of cells based on Alumina and Titania mesoporous layer are compared.

Modal properties of disordered optical structures, including a 1D-like multilayer structure and a 2D planar slab, have been numerically simulated in the Mid-IR region. The amount of scattering and the disorder level have been varied. A Finite Element Method solver has been used to show the modal properties of these structures, highlighting the correlation between the spectral behavior and the amount of disorder. The quality factor has also been investigated. A statistical parameter, based on the definition of photons travel distance, has been proposed to give a measure of the disorder according to the modal properties. With the help of a Monte Carlo based software this parameter has been investigated to verify its suitability.

A compact polarization beam splitter (PBS) for silicon-based slot waveguides is proposed based on a multimode interference coupler, where an asymmetrical multimode waveguide (AMW), cut by a right angle at one corner, is employed to efficiently separate the TE and TM modes. With the unique modal properties of the slot waveguides and corresponding optimized designs, the input TE mode can almost pass through the AMW and then enter into the bar port, while a mirror image is formed at the cross port for the input TM mode due to the self-imaging effect. Meanwhile, tapered waveguide structures and S-bend are incorporated into the designed PBS for further enhancing the performance. According to the numerical results, a PBS with an AMW of 2.3 μm in length is achieved, where the extinction ratios are 16.6 and 20.9 dB, respectively, for TE and TM modes, and the insertion losses are 1.37 and 0.81 dB, respectively, at the wavelength of 1.55 μm. For keeping extinction ratios over 15 and 20 dB for TE and TM modes, the bandwidths are around 59 and 73 nm, respectively, both covering the entire C-band. In addition, field evolution along the propagation distance through the PBS is also demonstrated.

Focusing the light onto nanostructures thanks to spherical lenses is a first step to enhance the field, and is widely used in applications, in particular for enhancing non-linear effects like the second harmonic generation. Nonetheless, the electromagnetic response of such nanostructures, which have subwavelength patterns, to a focused beam can not be described by the simple ray tracing formalism. Here, we present a method to compute the response to a focused beam, based on the B-spline modal method. The simulation of a gaussian focused beam is obtained thanks to a truncated decomposition on plane waves computed on a single period, which limits the computation burden.

Two multi-semiconductor-laser (SL) topologies, based on mutually coupled semiconductor lasers - representing a startype and a mesh-type network - are evaluated in terms of their synchrony potential and their sensitivity towards critical SLs' intrinsic and operational parameters. The coupling topology, the coupling conditions and the values of key SL parameters determine the type of dynamics of the emitted optical signals. The number of nodes and the detuning in their fundamental properties have been assessed to be decisive in terms of efficiency and quality of synchronized outputs, as wells as for the overall dynamical map of the network. Our investigation mainly focuses on discrepancies in SL parameter values and their effect on the efficiency of synchronized dynamics. This type of investigation will provide preliminary guidelines on building experimentally large scale networks of coupled SLs under various coupling matrices that could support optical sensing or cryptographic applications.

A novel photonic analog-to-binary converter based on the first-order asynchronous delta-sigma modulation (ADSM) has been theoretically investigated and experimentally demonstrated. A fiber-optic prototype ADSM system is constructed and characterized. Delta-sigma modulation is a straightforward approach to A/D conversion because in this case an external clocking is not required and demodulation can be simply performed via a low-pass filtering process. To improve signal-to-noise ratio and thus system ENOB, a non-interferometric optical implementation has been constructed. The ADSM is comprised of three photonic devices: an inverted output photonic leaky integrator, bistable quantizer, and positive corrective feedback. The photonic integrator which is a recirculating loop performs the oversampling of an analog input using the cross-gain modulation in an SOA. We will show that the photonic ADSM produces an inverted non-return-to-zero (NRZ) pulse-density modulated output describing an input analog signal. This fiber-optic ADSM converts up to 7.6 MHz analog input at about 30 MS/s and effective ENOB of 6.

We report the on-chip generation and in-plane transmission of indistinguishable photons from a semiconductor quantum dot embedded in a photonic crystal waveguide. We demonstrate the indistinguishability of the in-plane photons by performing two-photon interference with light collected from the exit of the photonic crystal waveguide. Under continuous wave optical excitation, the interference visibility is measured to be 0.40 ± 0.04, limited by the temporal resolution of our single-photon detectors. Our results are in excellent agreement with our theoretical model, in which all the parameters are determined experimentally.

A comparative study of two different Photonic Integrated Circuits (PICs) structures for continuous-wave generation of millimeter-wave (MMW) signals is presented, each using a different approach. One approach is optical heterodyning, using an integrated dual-wavelength laser source based on Arrayed Waveguide Grating. The other is based on ModeLocked Laser Diodes (MLLDs). A novel building block -Multimode Interference Reflectors (MIRs) – is used to integrate on-chip both structures, without need of cleaved facets to define the laser cavity. This fact enables us to locate any of these structures at any location within the photonic chip. As will be shown, the MLLD structure provides a simple source for low frequencies. Higher frequencies are easier to achieve by optical heterodyne. Both types of structures have been fabricated on a generic foundry in a commercial MPW PIC technology.

In this paper, surface plasmon resonance triangular ring resonator (SPR-TRR) Vernier structure based on InP is simulated for index variation from 1.33 to 1.35. Sensing area of SPR-TRR is achieved to make an ultra-compact SPR mirror by deposition of Au film layer which is designed to deposit on vertex of TRR. The possibility of mass production is shown by a deposition of SPR mirror on the triangular ring resonator (TRR). Also, the sensitivity enhancement of an envelope signal for Vernier effect is confirmed by FDTD simulation compared to SPR-TRR. As simulation results, the sensitivity is enhanced 20 nm / RIU to 480 nm / RIU. Thus, SPR-TRR Vernier structure is used for a biosensor to enhance the sensitivity of biosensor.

In this paper, we proposed novel graphene-based tunable plasmonic metamaterial structures to realize transparency windows. The proposed structures are composed of a graphene layer perforated with a quadrupole slot structure and a dolmen-like slot structure, which could achieve single and multiple transparency windows, respectively. In both complementary structures, the transparency windows could be dynamically manipulated by varying the Fermi energy levels of the graphene layer through electrical gating. The presented complementary graphene-based metamaterial structures with multiple tunable transparency windows could open up new opportunities for potential applications in tunable multi-wavelength slow light devices and optical sensors.

In this paper, we proposed a novel cross-polarization converter that simultaneously works at two frequencies in the reflection mode, which is constructed of an L-shape perforated graphene sheet printed on a dielectric spacer backed by a gold layer. For the normal incidence, the optical rotation at these two working frequencies originates from the simultaneous excitation of both eigenmodes characterized as the localized surface plasmon resonances. In addition, both working frequencies can be tuned within a large frequency range by varying the Fermi energy of the graphene, which opens up tremendous opportunities to develop voltage-controlled tunable devices at mid-IR frequencies.

In this paper, we demonstrate a novel all-fiber current sensor using ordinary silica fiber and the fiber loop architecture that can be used to improve current sensitivity. In order to improve the efficiency of the sensor and reduce cost, we present a multichannel all-fiber current sensor based on the principle of time-division multiplexing. To illustrate the principle, we show the typical dual-channel all-fiber current sensor in our experiment. It shows that the currents at two different points can be measured simultaneously. In addition, we find by measurement that the dual-channel fiber current sensor has good linear responses dependence of the variation of the degree of polarization ∆P on the current intensity I for two channels respectively. Every channel is affected by the current alone, requires a separate calibration.

Monolayer or few-layer molybdenum disulfide (MoS₂) has attracted increasing interests in studying light-induced electronic effect due to its prominent photo-responsivity at visible spectral range, fast photo-switching rate and high channel mobility. However, the atomically thin layers make the interaction between light and matter much weaker than that in bulk state, hampering its application in two-dimensional material optoelectronics. One of recent efforts was to utilize resonantly enhanced localized surface plasmon for boosting light-matter interaction in MoS₂ thin layer phototransistor. Randomly deposited metallic nano-particles were previously reported to modify surface of a back-gated MoS₂ transistor for increasing light absorption cross-section of the phototransistor. Wavelength-dependent photocurrent enhancement was observed. In this paper, we report on a back-gated multilayer MoS₂ field-effect-transistor (FET), whose surface is decorated with oriented gold nanobar array, of which the size of a single nanobar is 60nm:60nm:120nm. With these oriented nanostructures, photocurrent of the MoS₂ FET could be successfully manipulated by a linear polarized incident 633nm laser, which fell into the resonance band of nanobar structure. We find that the drain-source current follows cos²θ relationship with respect to the incident polarization angle. We attribute the polarization modulation effect to the localized enhancement nature of gold nanobar layer, where the plasmon enhancement occurs only when the polarization of incident laser parallels to the longitudinal axis of nanobars and when the incident wavelength matches the resonance absorption of nanobars simultaneously. Our results indicate a promising application of polarization-dependent plasmonic manipulation in two-dimension semiconductor materials and devices.

The mid-infrared (MIR) region is one of the most thriving spectral regions as it contains the vibrational resonances of several molecules of interest, as well as the absorption bands for hot bodies. In this work, we propose a novel dielectric waveguide that confines the light in a nanoscale air gap. This dielectric waveguide is a suitable candidate for on-chip sensing. Detailed dispersion analysis of this 3D waveguide is also provided. The effect of the refractive index change in the gap is studied and shows very high sensitivity and causes significant changes in the modal parameters. We also show that these waveguide modes exhibit plasmonic-like characteristics at the MIR region with controllable plasma frequency, without the inclusion of any metals. This waveguide is also utilized in various on-chip applications with nanoscale confinement at the MIR region.

A new technique for Automatic Modulation Format Recognition (AMFR) in next generation optical communication networks is presented. This technique uses the Artificial Neural Network (ANN) in conjunction with the features of Linear Optical Sampling (LOS) of the detected signal at high bit rates using direct detection or coherent detection. The use of LOS method for this purpose mainly driven by the increase of bit rates which enables the measurement of eye diagrams. The efficiency of this technique is demonstrated under different transmission impairments such as chromatic dispersion (CD) in the range of -500 to 500 ps/nm, differential group delay (DGD) in the range of 0-15 ps and the optical signal tonoise ratio (OSNR) in the range of 10-30 dB. The results of numerical simulation for various modulation formats demonstrate successful recognition from a known bit rates with a higher estimation accuracy, which exceeds 99.8%.

We have analyzed a hybrid photonic-plasmonic crystal nanocavity consisting of a silicon grating nanowire adjacent to a metal surface with a gain gap between. The hybrid plasmonic cavity modes are highly confined in the gap due to the coupling of photonic crystal cavity modes and surface plasmonic gap modes. Using the finite-element method, we numerically solve guided modes of the hybrid plasmonic waveguide at a wavelength of 1.55 μm. The modal characteristics such as waveguide confinement factors and modal losses of the fundamental hybrid plasmonic modes are explored as a function of the groove depth at various gap heights. After that, we show the band structure of the hybrid crystal modes, corresponding to a wide band gap of 17.8 THz. To effectively trap the optical modes, we introduce a single defect into the hybrid crystal. At a deep sub-wavelength defect length as small as 180 nm, the resonant mode exhibits a high quality factor of 566.5 and an ultrasmall mode volume of 0.00186 (λ/n) ³ at the resonance wavelength of 1.55 μm. In comparison to the conventional photonic crystal nanowire cavity in the absence of metal surface, the figure of merit Q/V_m is enormously enhanced around 15 times. The proposed nanocavities open up the opportunities for various applications with strong light-matter interaction such as nanolasers and biosensors.

Superconducting nanowire single-photon detectors (SNSPDs) with a composite optical structure composed of phase-grating and optical cavity structures are designed to enhance system detection efficiency and count rates. Numerical simulation by finite-difference time-domain method shows that the photon absorption capacity of SNSPDs with a composite optical structure can be enhanced significantly by adjusting the parameters of the phase-grating and optical cavity structures. The absorption capacity of the superconducting nanowires reached 69.8% at the wavelength of 850 nm with 0.3 filling factor. When the filling factor was reduced to only 0.08, the absorption capacity is still 48.52%. It greatly decreased the kinetic inductance of SNSPDs, and improved the count rates.

The reduced peak efficiency and the efficiency droop afterward, i.e. the degraded efficiency, of blue InGaN lightemitting diodes (LEDs) is investigated numerically. It is depicted that the joint effects of multiple factors, including the influences of polarization-induced electric field, the phenomenon of current crowding, and the Auger and ShockleyRead-Hall (SRH) recombinations, are responsible for the degraded efficiency. Among them, the severe SRH recombination due to the poor crystalline quality is the main cause of reduced peak efficiency, while the serious Auger recombination resulted from high Auger recombination coefficient and non-uniform carrier distribution of the active region is the major factor contributing to efficiency droop. It is shown that the strong built-in polarization field and the crowded current flow will result in the nonuniform carrier distribution, and thus enlarge the Auger losses and the efficiency droop.

Microwave frequency combs utilizing hybrid optical injections schemes by varying the operational parameters, injection strength, repetition frequency, and detuning frequency are demonstrated and characterized. The dynamical hybrid optical injections are realized by both optical pulse injection and optical cw injection to the slave laser simultaneously under the condition of zero detuning frequency between two injecting source lasers. For pure pulse injection case, the amplitude variation of ±27.3 dB in a 30 GHz range is obtained. By further applying the injection strength of the cw injection to the pulses injected semiconductor laser, the amplitude variation of ±3.3 dB in a 30 GHz range in microwave frequency combs are observed when operating the cw injection system in a stable locking state. In order to examine the microwave frequency comb precisely, each operational parameters of the hybrid optical injections schemes are analyzed. The amplitude variation of microwave frequency combs is also strongly influenced by operating the cw injection system in different states. Comparing to the cw injection system operated in period-one states, the amplitude variation is reduced when operated in the stable locking states. Moreover, the bandwidth broadening in microwave frequency comb is expected when the cw injection system operating in a stable locking state. In this paper, strongly improve the amplitude variation of the microwave frequency combs generated utilizing hybrid injections scheme compared to single injection case are obtained and compared.

In this work the influence of nanoscale particles caused by processing excursions during back end of line (BEOL) processing on top of the photodiode active region was examined. To investigate the influence of the particles on the photodiode performance, wafer level optical responsivity measurements were done. In addition to the measurements the effect of the particles was simulated with a simplified model based on a modified transfer matrix method (MTMM)¹ . The simulation and measurements are in very good agreement with each other and lead to the conclusion that even though some decrease of sensitivity was observed, the overall system variability was reduced by the presence of particles. Furthermore, the influence of the dielectric stack layer thickness variability on the photon flux density is reduced.

Equivalent circuit models of a transistor laser are used to investigate the suitability of this relatively new device for analog microwave photonic links. The three-terminal nature of the device enables transistor-based circuit design techniques to be applied to optoelectronic transmitter design. To this end, we investigate the application of balanced microwave amplifier topologies in order to enable low-noise links to be realized with reduced intermodulation distortion and improved RF impedance matching compared to conventional microwave photonic links.

Proposed in this manuscript is a novel taper geometry, the constant-loss taper (CLT). This geometry is derived with 1D slabs of silicon embedded in silicon dioxide using coupled-mode theory (CMT). The efficiency of the CLT is compared to both linear and parabolic tapers using CMT and 2D finite-difference time-domain simulations. It is shown that over a short 2D, 4.45 μm long taper the CLT's mode conversion efficiency is ~90% which is 10% and 18% more efficient than a 2D parabolic or linear taper, respectively.

A novel photonic analog-to-digital converter (ADC) based on asynchronous delta-sigma modulation (ADSM) has been investigated. The architecture utilizes an optical leaky integrator, optoelectronic bistable quantizer, and positive corrective feedback for a non-interferometric optical implementation of ADSM. The principles of the proposed 1^st –order ADSM are mathematically modeled and simulated.

In recent times, much research in the field of complementary metal oxide semiconductor (CMOS) image sensors (CISs) regarding plasmonic color filters (PCFs) has been reported. In this paper, we investigated the influence of vertically asymmetrical metallic apertures on the extraordinary optical transmission of PCFs. We designed a structural model of the asymmetric cylindrical aperture. In addition, we simulated the spectral variation in the wavelength transmission. For the simulation, we used a commercial computer simulation tool utilizing the FDTD method. SiO₂ was used as the substrate insulator, top-side insulator, and the fill material in the cylindrical aperture. We applied Au as the metal layer; dispersion information for Au was derived from the Lorentz–Drude model. We also presented the electric field distribution under several different conditions at the peak wavelength of the calculated transmission spectrum. Furthermore, we determined the transmittance spectral characteristics and the peak transmittance under several different conditions.

Engineering of electronic energy band structure in graphene based nanostructures has several potential applications. Substrate induced bandgap opening in graphene results several optoelectronic properties due to the inter-band transitions. Various defects like structures, including Stone-Walls and higher-order defects are observed when a graphene sheet is exfoliated from graphite and in many other growth conditions. Existence of defect in graphene based nanostructures may cause changes in optoelectronic properties. Defect engineered graphene on silicon system are considered in this paper to study the tunability of optoelectronic properties. Graphene on silicon atomic system is equilibrated using molecular dynamics simulation scheme. Based on this study, we confirm the existence of a stable super-lattice. Density functional calculations are employed to determine the energy band structure for the super-lattice. Increase in the optical energy bandgap is observed with increasing of order of the complexity in the defect structure. Optical conductivity is computed as a function of incident electromagnetic energy which is also increasing with increase in the defect order. Tunability in optoelectronic properties will be useful in understanding graphene based design of photodetectors, photodiodes and tunnelling transistors.