Fiber Bragg grating (FBG) based wavelength division multiplexer (WDM) optical cross connect (OXC) is of great importance, which has the advantages of good performance and potential low cost. Optical crosstalk plays a major role in limiting practical implementations of an OXC. Crosstalk analyses presented so far generally focus on the traditional multiplexer/demultiplexer and optical switch based OXC architecture. In this paper, optical crosstalk in multiwavelength reconfigureable nonblocking OXCs using tunable FBGs and optical circulators (OCs) is discussed. Two crosstalk mechanisms, intraband and interband, are identified and analytical models are presented. Both first-order and second-order crosstalk contributions have been studied. For the intraband crosstalk, results show that the worst case coherent crosstalk is the dominant crosstalk, which is ~ 23 - 25 dB higher than the incoherent crosstalk, depending on the switching states of the 2 x 2 OXCs. For the interband crosstalk, results show that it is nonaccumulative and becomes very small with the increase of the number of fibers or the cascaded stages of 2 x 2 OXCs. However it deteriorates with the increase of the number of wavelengths per fiber.

Quantum photonic informatics involves manipulation and processing of information at a photon energy level. The qu-bit with optical modes containing one photon energy is described and photonic gates representing its quantum states are given and expanded into quantum systems and networks for computing and information processing. Integrated photonic devices are proposed for implementation of the quantum gates and networks and case studies are examined for further expansion and implementation of quantum algorithms.

A flexible crosstalk analysis method based on scattering matrix for optical cross connect(OXC) with various topology is proposed. In this method, all components in the OXC are treated as multiple ports sub-networks represented using scattering parameters (S parameters). The crosstalk can be precisely computed using measured S parameters of every components. As an example, a 4 + 4 fiber bragg grating and optical circulator (FBG-OC) based reconfigurable nonblocking OXC is studied using the method.

We propose to use nonlinear optical (NLO) polymer to fabricate microring resonator device for all-optical switching application. In the proposed device NLO polymer provides the saturable absorption nonlinearity and microring resonator provides the feedback needed for optical bistability. Waveguide confinement and field intensity build-up in the ring resonator both facilitate the nonlinear optical process, making it possible to achieve low switching intensity. Moreover, the size of microrings is in the range of several tens of micro-meters, which is promising for high-speed optical switching as well as for high-density integration. We present detailed analysis of the device operation and identify key facts for the optimization of the devices. We propose to use nanoimprinting lithography technique to create microring resonator structures in NLO polymers, and show our initial results that prove the feasibility of this approach.

It is shown that the potential barrier introduced by p delta doping in n-i-n diode not only reduce the dark current but also enhance the responsivity. This was applied to both QWIP and QDIP. The QWIP is made of In0.3Ga0.7As/GaAs multiple quantum wells and the QDIP is made of p type self assembled InAs/GaAs quantum dots. The dark currents are reduced by an order of magnitude at 77K and the detectivities are increased. Thermal activation energies of PL peaks from various QD structures are investigated, which include the effects of barrier height , QD size and barrier materials.

Inter-sublevel transitions in InGaAs/AlGaAs quantum dots (QDs) in the mid-infrared (MIR) wavelength range are investigated by means of absorption and optically and electrically pumped emission spectroscopy. Charging dependent energy shifts of inter-sublevel transitions observed in calorimetric absorption spectra are attributed to few-particle effects in the QDs. MIR emission from near-infrared QD lasers is observed in the MIR lasing mode below threshold, which is confirmed by a theoretical modelling of such a bipolar lasing device. In contrast, spontaneous MIR emission is recorded for optically pumped Qds.

Photonic crystals (PCs) having two-dimensional (2D) periodicity on a length scale of 320-450 nm were fabricated by electron beam lithography in combination with high- aspect-ratio dry etching. To achieve three-dimensional control of the optical properties, three kinds of dielectric waveguide structures based on AlGaAs heterostructures, that is, semiconductor-clad (SC), air-bridge (AB), and oxide-clad (OC) structures, were investigated. Observation of light propagating through such photonic crystal devices was employed by optical transmission measurements. Clear photonic bandgap effects resulting in 30-dB attentuation of the transmitted light could be observed in the the bandgap regions. The measured results were in good agreement with calculated band-structures and transmission spectra using a Fine-Difference Time-Domain (FDTD) method. Straight, sixty degree-bent and Y-branch defect waveguides (D-WGs) in a 2D- PC slab were fabricated, and the resulting light propagation characteristics were measured by two methods. One was measurement of transmission spectra at wavelengths ranging from 850 to 1100nm. Another was plan-view observation of the optical beam race trace along the waveguide measured with an IR-vidicon camera. Three-dimensional FDTD simulations for the band structure and transmission spectra in the air- bridge slab with and without defect waveguides resulted in the appearance of four defect propagation modes specific to the defect waveguide, between two slab modes for the defect- free PC slab. As an example of the future-promising application of the 2D-PC slab, an ultra-small and ultra-fast optical switching device including quantum dots as large optical non-linearity (%chi^3+S) media is proposed. To demonstrate such a device, recent advancement of a nano- probe assisted processing of arrayed quantum dots is discussed. Achievement of this technology will provide us with a possibility of extremely miniaturized all-optical switching devices in the OTDM optical communication network.

The effects of liquid crystal (LC) infiltration on the photonic band gaps (PBGs) of two-dimensional (2D) metallic photonic crystals (PCs)are investigated by theoretical calculation. Contrary to the LC-infiltrated dielectric photonic crystals, the infiltration of LCs into 2D metallic PCs is found to enlarge PBGs and create another PBGs in a frequency range higher than that of the original PBG. The change of refractive index due to the phase transition of LCs affects both edges of PBGs so that the positions of PBGs show rather large temperature dependence near the phase transition temperature. Thus metallic PCs infiltrated with LCs can overcome the drawbacks of LC infiltration in dielectric PCs, i.e., the band gap narrowing and weak tunabilty of band gap. The usefulness of LC infiltration in the implementation of 2D or 3D tunable metallic photonic crystals is also discussed.

Self-organization of sub-micron particles in the colloidal suspensions is an attractive phenomenon in the manufacture of photonic crystals. In this report, we carry out Monte Carlo simulations of the self-arrangement of particles under the illumination of the focused laser beam. It is based on the Metropolis algorithm with a periodic boundary condition for a canonical ensemble. The radiation pressure in the focused laser beam and the interaction induced by both the van der Waals attraction and the screened Coulomb repulsion exerted between particles are taking into account. Because the simulations are restricted to the two-dimensional space, the radiation pressure is approximated to a gradient force that makes to move particles into the area with the stronger intensity. We successfully show that particles are gathered into the illuminating area by the gradient force of the focused laser beam and spontaneously organize the periodic structure. On the other hand, the periodic structure is not organized under the weak radiation pressure though the particles are gathered into the illuminated area.

We have performed calculations using the Transfer Matrix method to study the photonic band gap properties of bare opals of different diameters, different thicknesses, sintered opals with the filling fractions varying between 0.74 and 1.00, partial and complete coating with semiconducting GaN and lastly, inverted opals. Two prominent directions [100] and [111] have been analyzed. Sintering improves the gap and shifts the energy range of its occurrence, while partial coating gives a better bandgap than complete coating. Inverted opals with semiconductor background shows a gap with transmission decreasing to much lower values, as expected due to an improvement in dielectric contrast.

The colloidal crystallization of fine particles is a phenomenon of great interest in connection with the fabrication of photonic crystals. In this report, a new fabrication method is proposed, which is based on self- arrangement and self-assembly of particles generated under the radiation pressure of a focused laser beam, i.e., gradient and scattering forces, and capillary force occurred during the desiccation process, respectively. The hexagonal structure in the Fourier-transformed patterns of 2D colloidal crystals shows that a triangular lattice structure is successfully fabricated by the proposed method. This report is concerned with the principle of newly proposed method, capturing and self-arranging particles by the radiation pressure, self-assembling particles by the capillary force, enlarging the colloidal crystal, and verifying the production of the triangular lattice structure in the crystal of particles.

Polymers have many interesting characteristics that make them attractive for integrated optics applications. Polymeric materials and various fabrication techniques used currently will be discussed and compared, and optical waveguides and devices are reviewed.

Room temperature ohmic contacts to p- and n-type GaN using surface treatments were applied to the fabrication of GaN blue light emitting diode (LED). The state-of-the-art LED operation of the forward voltage of 3.1 V at the injection current of 20 mA was demonstrated without annealing processes. The surface treatment on p-type GaN using aqua regia solution caused the contact resistivity to decrease by three orders of magnitude. The inductively coupled plasma treatment on n-type GaN resulted in the contact resistivity of ~ 10E-6 ohm-cm2 at as-deposited state. Both treatments allowed the room temperature ohmic contacts to be realized on both substrates. Angle resolved synchrotron x-ray photoelectron spectroscopy was employed to examine the atomic composition at the treated surface. From this, the formation of ohmic contacts was deduced as due to the production of vacancies below the contact, that is, Ga vacancies for p-type contact and N vacancies for n-type one.

Deep level transient spectroscopy (DLTS) characterization of defects in InGaAlP films grown using two different V/III ratios was carried out. Electron trap levels with activation energies of 0.42 eV and 0.78 eV were detected in the sample with V/III ratio of 50 and 75 respectively, using isothermal DLTS. In this paper, the severe temperature dependence of the DLTS signals observed for these two trap levels is explained in terms of the presence of noticeable capture barriers for electrons. The capture barrier heights of 0.27 and 0.13 eV were estimated for trap levels of 0.42 eV and 0.78 eV respectively. It is believed that these two trap levels are associated with extended defects based on the observation of logarithmic dependence of the DLTS signal on filling pulse width. This is further supported by the observation of a broader temperature scan spectrum in the sample with V/III ratio of 75. For the sample with a V/III ratio of 50, a monotonic increase in DLTS signal with temperature was observed for temperature scan DLTS up to the upper limit of the system. Although the two defect levels observed in this study appear both to be related to extended defects, they are related to two different defects simply due to the observation of much different thermal signatures for these two defects. The results indicate that a V/III ratio of 50 is a better choice as the associated defect has a smaller capture cross-section and a larger capture barrier.

We present the first demonstration of reproducible harmonic modelocked operation from a novel design of monolithic semiconductor laser comprising a compound cavity formed by a 1-D photonic-bandgap (PBG) mirror. Modelocking is achieved at a harmonic of the fundamental round-trip frequency with pulse repetition rates from 131 GHz up to a record high frequency of 2.1 THz. The devices are fabricated from GaAs/AlGaAs material emitting at a wavelength of 860 nm and incorporate two gain sections with an etched PBG reflector between them, and a saturable absorber section. Autocorrelation studies are reported, which allow the device behaviour for different modelocking frequencies, compound cavity ratios, and type and number of intra-cavity reflectors to be analyzed. The highly reflective PBG microstructures are shown to be essential for subharmonic-free modelocking operation of the high-frequency devices. We have also demonstrated that the multi-slot PBG reflector can be replaced by two separate slots with smaller reflectivity. These lasers may find applications in terahertz imaging, medicine, ultrafast optical links, and atmospheric sensing.

We demonstrate a novel delay-line-free electro-optic sampling system by using a delay-time shifter which is modified from a microwave phase-locked loop. The ultrafast laser is inherently integrated with an electronic phase shifter which is modified from a microwave phase-locked loop. The voltage-controlled phase-shift as well as time- delay of the optical pulse is linear in the tuning of up to 1.9 period. The waveform sampling of the positive ECL signals generated from microwave frequency divider by using this system is demonstrated. The sampling results are compared with the same signals measured by conventional sampling scope. The distorted waveform of the ECL signal frequency-prescaled from microwave oscillator operated at high output level is observed. The divisor of the frequency presclar is found to vary from 2 to 5 at input power of less than -14DBm.

Monolithic colliding pulse mode-locked (CPM) lasers operating at 1.5 +m and 36 GHz repetition frequency were fabricated on semi-insulating substrates. An RF electrical signal at a subharmonic frequency was injected into the saturable absorber at various injected RF power levels, and both the phase noise and timing jitter were characterised. Under fundamental hybrid mode-locking (FH-ML) case, the worst-case timing jitter was reduced from 4.8 ps to 0.69 ps with an injected RF power of +8 dBm. For the second order and third order subharmonic hybrid mode-locking (SH-ML) cases, the timing jitter was reduced to 0.32 ps and 0.45 ps respectively with an injected RF power of +15 dBm. For both the SH-ML cases, the amplitude modulations imposed by the subharmonic driving frequencies were found to be very small.

We investigated the intersubband transition in semiconductor quantum wells for ultrafast all-optical switching, proposing the use of InGaAs/AlAsSb coupled double quantum well structures on InP to facilitate intersubband transitions at optical-communication wavelengths, and to reduce the intersubband absorption recovery time from several picoseconds to a few hundred femtoseconds. We obtained high-quality InGaAs/AlAsSb quantum well structures by developing an As-termination technique at the interfaces between quantum wells and barriers, using molecular beam epitaxy. Near-infrared intersubband transitions down to the optical-communication band were realized in InGaAs/AlAsSb single quantum well and coupled double quantum well structures, and picosecond and subpicosecond responses were observed using pump-probe experiments, while optical nonlinearities were estimated from intersubband absorption saturation measurements. Also demonstrated was an all-optical demultiplexing of single signal pulses from 1 Tb/s signal pulse trains at 1.55 um using an InGaAs/AlAsSb coupled double quantum well waveguide. The results indicate that the intersubband transition in this material is very useful for ultrafast all-optical switching.

Here, we refer our new proposal of applying multi-valued logic (particularly tristate logic) to develop logic gates and systems for arithmetic operation. Space-variant approach is used here to implement the functioning. Also triple input image detection is done here.

In this article, the feasibility of a programmable diffraction grating based on the interaction of light and controlled interface charges is explored. The diffraction is obtained by stacking the plasma wave modulator/switch, and programming is realized by controlling the densities of interface charges via independent DC transverse voltages as discussed throughout. It is shown that the diffraction efficiency, polarization, and even the direction of reflection and transmission modes can be controlled.

In this report, we experiment on the two-dimensional image reading and writing in the photorefractive nondestructive memory with BaTiO3 crystal. The great extension of the reading time is archived by use of the grating maintenance technique with optical feedback. By calculating the temporal property of the output beam intensity and the index grating amplitude under the incident conditions of the conventional readout technique and our readout technique, we estimate the feedback rate and the coupling strength for high output generating efficiency. We experiment on the two-dimensional image reading and writing with BaTiO3 crystal, and succeed at over 20 minutes reading without image degradation.

In this report, we study the automatic data duplication function in an all-optical fault tolerant holographic memory with two photorefractive crystals. In this memory, when a partial data are dropout, the dropout event is detected and the dropout data are restored automatically without any electronic device. We analyze the dependency of the data restoring performance on the frequency of dropout event. We calculate the MTTR (Mean Time To Recovery), in case the data in one crystal are dropout, then the data in another crystal are also lost before the dropout data haven't been completely yet. On the assumption that the data in one of the crystal are dropout, we conduct the experiment in the data recovery on this memory to examine the performance of restoring the data. We achieve that the MTTR is 1seconds and the data are continuously readout over 550 seconds when the stored data in one of the crystal are lost.

The amplification of picosecond optical pulse train with Gigabit repetition rate by using a traveling-wave semiconductor optical amplifier (TWSOA) is studies. The effect of driven current and operating temperature on the performance of TWSOA in amplification of picosecond negatively chirped optical pulses from gain-switched laser diode (GSLD) are characterized. The maximum output peak power and gain of the TWSOA operated at pulse mode are determined. The distortion in trailing edge of pulse shape is significant under the TWSOA operating at higher driven levels, such a nonlinear phenomenon inherent with the TWSOA leads to the broadening of pulsewidth and the saturation of peak power and gain of optical pulses. The optimized operating parameters such as the driven levels and temperatures of TWSOA and GSLD for generating and amplifying shorter optical pulse with higher gain are obtained, which are at below threshold and lower than room temperature conditions. The shortest pulse generated from GSLD and amplified by the TWSOA are 13 ps and 17 ps, respectively.

We propose all-optical switching schemes using a single three-level atomic system placed within a 3D photonic crystal that exhibits a complete 3D photonic band gap. The optical schemes we propose can be classified into two types with respect to a physical process that causes the switching effect. One switching type is mediated by changing an atom-field coupling strength. The other switching type is mediated by controlling quantum interference. Furthermore, we consider conditions of realizing a wide range of signals, which contributes to an improvement of the Signal to Noise ratio. The phases and strengths of the external laser fields required for the all-optical switching are revealed. Next, we estimate their switching times. Using these results, we propose the fastest scheme for every configuration of the atomic system, which is important for realizing a high-speed optical memory or switching device on an atomic scale that can be used in novel optical integrated systems, such as quantum computers.

We propose an all-optical interconnection with pattern memory function by a photorefractive full-linear resonator with a beam splitter(BS) and a self-pumped phase conjugate mirror(CAT). This interconnection utilizes the oscillation phenomenon between the BS and the CAT. This resonance beam rewrites and sustains the connection pattern continuously, which is once configured by the writing beam, after the writing beam is turned off. We analyze the optimum reflectivity of the BS and the CAT, which determines the feedback rate of the resonation, for high connection efficiency. We also analyze the coupling strength threshold of the photorefractive crystal for the sustentation of the connection. We experiment on the photorefractive full-linear resonator in order to examine the efficiency and the sustentation time of the connection.

We have proposed an all-optical memory with authentication and unlawful access detection using photorefractive four-wave mixing. If the data is read out by the reading beam with the improper key, the output intensity is scarcely zero and any output isn't obtained. Therefore we can judge at a glance whether or not the used decoding key is the proper key. We analyze the diffraction efficiency with consideration of the phase mismatching to evaluate the fidelity of the hologram. In this analysis, we examine the property of the crystal that depends on three-dimensional coupling coefficient. We simulate the encoding and decoding process with some image data in this all-optical memory with authentication and unlawful access detection. We show that the encoded image is restored to its original image in case of retrieving with the proper key, on the other hand the retrieved image of which intensity is scarcely zero is obtained in case of retrieving with the improper key.