This PDF file contains the front matter associated with SPIE Proceedings Volume 8308, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Slow light is generated via the gain mechanisms of nonlinear optical phenomena-- stimulated stimulated Brillouin scattering in optical fiber. Slow light is characterized in terms of Brillouin threshold, gain spectrum, Brillouin frequency shift by using optical heterodyne detection. According to the measured Brillouin frequency shift, we set our signal frequency in the gain region by manual matching method to get the maximum gain, and the gain bandwidth is broadened to 450MHz using a phrase-modulated pump. A delay of 32ns is achieved for the 500ns input signal when the gain is 15dB.

Heterodyne method is used to monitor Brillouin gain spectrum in our slow light system. Accurate continuous Brillouin gain spectrum is obtained and makes tunable laser accessible to adjusting wavelength of signal light into the spectrum region. Maximum 32ns delay is achieved by 600MHz broadband Brillouin gain bandwidth.

We propose an all-optical edge detector for the high-speed non-return-to-zero (NRZ) signals by employing a Mach-Zehnder interferometer (MZI) incorporating semiconductor optical amplifiers (SOAs), where the cross phase modulation (XPM) in SOA is exploited. The basic working principle of the proposed edge detector is that the CW probes in the upper and bottom arms always undergo a phase difference of π, except during the leading and tailing transition edges of the NRZ signals. Therefore, the output after the two probes interfering at the constructive port of the MZI will be a series of pulses at only the edges of the NRZ signals. The output signals of the edge detectors are numerically evaluated in terms of the Q factor (>20dB) and extinction ratio (>11dB) at 20 and 40 Gb/s, which indicate the high quality of output.

We propose a new type of grating-assisted microring (GAMR) structure with Bragg gratings placed on microring's arms. Two Fabry-Perot resonances interact with microring resonance, resulting in GAMR's unique amplitude and phase spectra. The structure's characteristics are analytically studied using coupled mode theory and numerically verified by 2D-FDTD. With proper cavity lengths, GAMR exhibits an electromagnetically induced transparency (EIT)-like spectrum. The ultra-narrow resonance can be used for sensing, modulation, and other applications.

We demonstrated and fabricated a 20μm-long ultra-compact variable optical attenuator based on thermo-optical effect with slow light photonic crystal waveguide (PCWG). In simulation, we optimize the line-defect width and radius/period ratio (r/a) of the PCWG for deep photonic band gap and large slope photonic band edge. An r/a=140nm/410nm W1 PCWG is selected for its -60dB depth and 36dB variable attenuation range when the tunable refractive index change is 0.01. We also study different shapes of micro-heaters for low power consumption and high heat transfer efficiency. A 24.6mW and 75.9% heat transfer efficiency are achieved in a 2μm-wide right-angle-shaped micro-heater. In experiment, A 4.6nm red shift at the cutoff wavelength of the fundamental mode and a 10dB tunable attenuation range are achieved through tuning the temperature of the W1 PCWG by an 4.7μm-wide aluminum micro-heater with a maximum power consumption as low as 30.7mW.

We proposed a compact surface wave polarization splitter based on the metallic-dielectric-air (MDA) waveguide with an slit surrounded by asymmetric corrugations. The incident light coupled to the MDA waveguide through the aperture is split into TE- and TM-polarized electromagnetic surface modes by the polarization-sensitive corrugations on each side. Polarization extinction ratios better than 20 dB are achieved for both polarizations. The structure would be interesting for a variety of optical devices and nanophotonics.

We demonstrated experimentally 40 Gbit/s all-optical format conversions between return-to-zero (RZ) and nonreturn-to- zero (NRZ) using a fiber delay interferometer (FDI) and a single semiconductor optical amplifier (SOA). Firstly, 40 Gbit/s data format conversion from RZ to NRZ is realized using a FDI with temperature control and an optical bandpass filter (BPF). Then, 40 Gbit/s data format conversion from NRZ to RZ is implemented, using four-wave mixing (FWM) effect of SOA, by injecting synchronously NRZ signal and clock pulses into a single SOA. Presented method has some distinct advantages including multi-channel parallel processing, easy integration, convenient tuning, good stability, and so on, which has potential to be used in future optical networks that could combine wavelength division multiplexing (WDM) and optical time domain multiplexing (OTDM) transmission techniques.

A novel scheme of Non-Return-to-Zero (NRZ) all-optical wavelength conversion is proposed using a semiconductor optical amplifier based Mach-Zehnder interferometer (SOA-MZI), where the complementary NRZ data is used to mitigate SOA patterning effect. The performances of the wavelength converters are numerically evaluated in terms of the waveform, eye-diagram and Q factor of the output signals at 40 Gb/s, using a time-domain SOA model. It is shown that the new complementary scheme significantly improves the Q factor of the converted signal from 3.8 to 8.1, compared with the traditional scheme.

Modulation Instability is known as intrinsic property of a nonlinear medium like Kerr medium or photorefractive medium; through the such media, the system behavior is possible to transit form stationary regime to chaotic regime; this paper deals with Modulation Instability (MI) in a nonlinear medium and investigates the analogy of MI of optical nonlinear medium and the consequent chaotic regime based on extracting Lyapunov exponent through the power spectrum and equivalently intensity-time diagram of MI; the experimental observation truly confirms the results of MI as the route to the chaotic regime.

A widely tunable distributed Bragg reflector (DBR) laser with gratings of simpler structure compare to other types of widely tunable (around 100 nm) lasers is proposed for achieving wide wavelength tuning range (> 100 nm), which consists a front reflector based on a normal sampled grating (SG) with a small duty ratio (the ratio of the grating pitch length to the sampling period), and a rear reflector based on a properly designed interleaved sampled grating (ISG). The interleaved sampled grating (ISG) has an advantage over other complex structures, it is easy for fabrication and reflection spectrum of the grating is stable while tuning. Simulation results demonstrated that characteristics of the reflection spectrums of the both reflectors is good for wide wavelength tuning, and the wavelength tuning range of a DBR laser based on this design can be over 100nm.

In this work we extract a novel formula for optical absorption coefficient of Quantum Dots (QDs) in frame of 8band k.p modeling. Also this is useful for any other several band k.p frame. Using this formula, we analyze and simulate absorption spectra for a typical InAs/In_0.4Ga_0.6As QD, both for TE and TM components of absorption spectra. Size and alloy fraction of QD is chosen such that the absorption spectra has some components around 1.55μm that will be applicable for single photon fiber optic communication.

A novel PbS quantum dots (QDs) fiber amplifier based on SiO₂ Sol-Gel method was proposed. The QDs doped SiO₂ films was deposited onto a fused tapered fiber coupler based on standard single mode fiber (SMF). With a 980 nm wavelength laser diode (LD) as the pump, 1550 nm signal and 980 nm pump light waves were injected into the tapered region simultaneously, through the evanescent wave, we obtained the gain at 1576 nm wavelength as high as 5 dB. The proposed fiber amplififier can implement the property of a small, integrated, high output, low noise, high gain, low cost, which meet the need of the future of optical fiber communication system.

Wavelength-scale defected circular microresonators with laterally confined metal layer are designed for directional emission from high Q confined modes by boundary element method (BEM), which is firstly applied to the multilayer structures. The influence of metal layer thickness on the mode filed patterns and Q factors are simulated. The results indicate that the thickness of the metal layer has a great effect on far-field emission patterns and the mode Q factors.

The electronic conductance at zero temperature through a quantum wire with side-attached asymmetric quantum ring (as a scatter system) is theoretically studied using the non-interacting Anderson tunneling Hamiltonian method. We show that the asymmetric configuration of QD- scatter system strongly impresses the amplitude and spectrum of quantum wire nanostructure transmission characteristics. It is shown that whenever the balanced number of quantum dots in two rings is substituted by unbalanced scheme, the number of forbidden mini-bands in quantum wire conductance increases and QW-nanostructure electronic conductance contains rich spectral properties due to appearance of the new anti-resonance and resonance points in spectrum. Considering the suitable gap between nano-rings can strengthen the amplitude of new resonant peaks in the QW conductance spectrum. The proposed asymmetric quantum ring scatter system idea in this paper opens a new insight on designing quantum wire nano structure for given electronic conductance.

In this work, a direct DQPSK receiver was fabricated, which comprises a polymer waveguide based delay-line interferometer (DLI); a polymer based optical hybrid, and two monolithic pairs of > 25 GHz bandwidth photodiodes that are vertically coupled to the polymer planar lightwave circuit (PLC) via integrated 45° mirrors. The common mode rejection ratio (CMRR) is used to characterize the performance of coherent receivers, by indicating the electrical power balance between the balanced detectors. However, the standard CMRR can only be measured when the PDs can be illuminated separately. Also, the standard CMRR does not take into account the errors in the relative phases of the receiver outputs. We introduce an adapted CMRR to characterize the direct receiver, which takes into account the unequal responsivities of the PDs, the uneven split of the input power by the DLI and hybrid, the phase error and the extinction ratio of the DLI and hybrid.

Off-plane band structure for triangular and square lattice with non-zero k_z component were calculated using Plane Wave Expansion Method. Both decreasing, finally breaking down of in-plane band gaps and emerging of new off-plane band gaps were observed with an increasing k_z. K_z component dependence of band gap was investigated in both triangular and square lattice, with varied air hole radius and dielectric constant.

In this paper, we propose the simplest one-dimensional grating waveguide to obtain the wideband slow light. An ideal band indicating group index of 18.3 and bandwidth of 10.3 nm is obtained by plane wave expansion method, which is also verified in the finite-difference time-domain numerical simulation when a Gaussian pulse with bandwidth of 10.3 nm is input into the grating waveguide. Thus, this simple one-dimensional grating waveguide is believed to be widely used as wideband and low loss slow light delay for optical buffering and signal processing.

We theoretically investigate the optical transmission through a subwavelength slit covered with a nanostrip and surrounded by corrugations in a metal film. Simulations results show that with a nanostrip on top of the slit, the optical transmission efficiency through the slit surrounded by grooves is greatly enhanced for various angles of incidence compared with the structure without the nanostrip. The nanostrip should be thick enough to result in an air nanocavity with high Q value and enhanced transmission efficiency.

Gain-assisted surface plasmon polaritons (SPPs) propagation is realized by electrical pumping the InGaAsP quantum wells (QWs) beneath the metal waveguide with asymmetric configuration. The long-range and short-range mode SPPs are analyzed theoretically and observed experimentally under different levels of current injection. It is demonstrated that among the complex SPP-coupled emission mechanisms, the short-range SPP is supported by stimulated amplification (SA) in electrically-pumped QWs, and increases robustly to as 1.6 times of the long-range mode SPP in output power over a travelling distance of 80μm. This stimulated SPP emission can be adopted for the minimization of the electrically controlled optical modulator.

In this work, we demonstrate the bulk self-alignment of gold nanorods (GNRs) dispersed in lyotropic nematic liquid crystals (LCs) with high optical absorption coefficient at the surface plasmon resonant wavelength. The polymer-coated GNRs which show spontaneous long-range orientational ordering along the director of LC host exhibit long-term stability as well as high concentration. External magnetic field and shearing allow for alignment and realignment of the orientation of gold nanorods by changing the director of the liquid crystal matrix. This results in a switchable polarization-sensitive surface plasmon resonance exhibiting stark differences from that of the same nanorods in isotropic fluids. The devise-scale bulk nanoparticle alignment may enable optical metamaterial mass production and control of surface plasmon resonance of nanoparticles.

A novel optical coupler to access free-space optical signals in subwavelength scale into dielectric waveguide via a plasmonic concentrator and a dielectric microring with field enhancement is proposed. The coupler is useful as it combines the plasmonic concentrator, which is used to access optical signals in subwavelength scale, a microring resonator for the coupling, with the dielectric waveguide for long distance optical transmission and processing.

Vertical-cavity surface-emitting lasers (VCSELs) using hybrid III-V / Si microcavities and based on double photonic crystal reflectors for the heterogeneous integration on complementary metal-oxidesilicon (CMOS) are presented. The latest achievements in optical mode engineering and technological processing are shown and discussed.

We investigate the influence of intense laser field on the energy state and optical properties induced by sublevels transition of quantum dot. The quantum system includes the piezoelectric effect that rarely mentioned in related references. The linear, nonlinear and total optical properties for two cases with different quantum dot radius are examined. The peak positions and the peak amplitudes of spectra change drastically due to different size of quantum dot.

A polymer optical waveguide amplifier based on PbS quantum dots (QDs) is demonstrated. It is fabricated by coating PbS quantum dots film on a SU-8 optical channel waveguide. The PbS QDs are synthesized by a combined colloidal and sol-gel method. The SU-8 polymer optical channel waveguide is fabricated by using a direct ultraviolet (UV) photolithography technology. With a Wavelength Division Multiplexer (WDM), the signal and pump waves can be combined and injected into the optical channel waveguide which is covered by QDs. The optical wave interacts with the PbS QDs through evanescent wave and is amplified. By using a 10mm length waveguide, a 3.0dB gain was observed at 1310nm wavelength with 980nm pump.

We have proposed a new dual band quantum cascade photodetector with ability of detecting UV and IR through two independent paths. Because of large band gap of GaN and AlGaN, we have used Al_xGa_1-xN/AlN quantum wells. For detecting of IR and UV intersubband and interband transitions have been used respectively. For IR and UV path we have achieved peak of Responsivity about 60 mA/W at 2.7 um and 25 mA/W at 245 nm at 300K respectively.

The ever growing demand for more bandwidth in high-performance computing (HPC) applications leads to a continuous replacement of traditional copper-based links by optical interconnects at ever shorter transmission distances. However, this trend results in a more stringent performance requirements for laser light sources utilized in new generations of optical interconnects in respect to single channel speed, packaging density, power consumption and temperature stability, to make the technology competitive and commercially viable. Vertical cavity surface emitting lasers operating at different wavelengths, e. g. 850 or 980 nm, represent one possible solution for the short distance high density interconnects in HPC applications. Here we present ultra-high speed highly temperature stable 980 nm VCSELs operating error-free at the record high bit rate of 44 Gbit/s at room temperature and 38 Gbit/s at 85 °C for future interand intra-chip, and module-to-module optical links. Next we present high speed extremely energy efficient 850 nm VCSELs with record low energy consumptions of only 83 fJ/bit while operating at 17 Gbit/s and of only 117 fJ/bit at 25 Gbit/s. Our VCSELs enable ecologically sound and economically practical HPC designs.

We report on the development of 25Gb/s 850nm VCSEL and PD components for efficient short-reach optical fiber communication systems. VCSELs with the aperture size 6-7μm show the highest -3dB bandwidth (~20GHz) and Dfactor (~8Ghz/mA^1/2). K-factor is less than 0.25ns for VCSEL with 6 μm aperture. Eye diagrams are clearly open at 25C up to 35Gb/s. The dark current of PDs remain below 1nA at T < 50°C and below 10nA when T < 90°C out to -10V. The extracted PD capacity is linearly proportional to the detector area and less than 200fF even for 45μm PD diameter. Due to elimination of contribution of diffusion process and quite small capacitance of the depletion region eye diagrams are opened at 28Gb/s, even for the PDs with the largest active diameters. Using 35μm PD and 6μm VCSEL error-free 25Gb/s optical fiber communication links were tested over lengths of 203m and 103m at 25°C and 85°C, respectively. Received optical power for the lowest BER is at both temperatures smaller than -4dBm. Obtained results indicate that from the speed and power dissipation perspective developed high-speed CSELs and PDs are suitable for applications in the next generation of short-reach multimode optical fiber interconnects.

Photosensors based on quantum dot and star like PbS has been successfully fabricated. Lead sulfides were synthesized by sonochemical and hydrothermal methods and coated on Cu interdigitated electrodes. The current-voltage (I-V) characteristics show linear and exponential behavior for quantum dots and star like PbS respectively. The photosensitivity is high for fabricated detectors by star like PbS. However, fast response time was observed for the detector fabricated by quantum dots.

We experimentally demonstrated four- and five-port non-blocking optical routers for photonic networks-on-chip. The optical routers are based on cascaded microring resonators. New topology design reduces the number of microring resonators and crossings, improving the performances in terms of tuning power consumption, optical loss, crosstalk and channel uniformity of the optical routers. The efficient footprints are 300x340 μm² and 440x660 μm² for fourand five-port optical routers, respectively. Static spectrum tests show that the 3-dB bandwidths are larger than 0.12 nm and 0.31 nm, the extinction ratios are larger than 13 dB and 20 dB for through ports, 30 dB and 16 dB for drop ports, for four- and five-port optical routers, respectively. Moreover, routing functionality and signal integrity are verified by 12.5 Gbps high-speed signal transmission experiments using the NRZ 231-1 PRBS pattern.

A novel ultra-short polarization beam splitter (PBS) based on a bent directional coupler is proposed. The bent directional coupler has two bent optical waveguides with different core widths, which is designed to have phase-matching for TM polarization while there is a significant phase-mismatch for TE polarization. Therefore, the TM polarized light can be coupled from the narrow input waveguide to the adjacent wide waveguide while the TE polarization goes through the coupling region without significant coupling. An ultra-short (<10μm-long) PBS is designed based on silicon-on-insulator nanowires and the length of the bent coupling region is as small as 4.5μm when choosing the gap width as 200nm (large enough to simplify the fabrication). The numerical simulations show that the present PBS has a good fabrication tolerance for the variation of the waveguide width (more than ±60nm) and a very broad band (~200nm) for an extinction ratio of >10dB.

Grating couplers are widely investigated as a coupling interface between silicon-on-insulator waveguides and optical fibers. In this work, novel grating couplers based on strip poly-Si are proposed. This structure utilizes the poly-Si gate layer of the CMOS MOSFETs, and thus enables grating couplers integrated with CMOS circuits without adding any additional masks and process steps. Simulation results show that a coupling efficiency over 60% can be achieved between silicon-on-insulator waveguides and fibers.

We present an analysis of polarization sensitive electro-optic measurement using Jones matrix formulation. Based on our formulation, we present an optimisation of the angle of incidence within the electro-optic probe and its ability to measure electric-fields in a three dimensional Cartesian coordinate system.

This research is based on the Fresnel's equations and the ellipsometric technique that investigate the sample of SiO₂ thinfilm on Si substrate. The investigation is made by a probing beam which is in the form of a rotating linearly polarized light generated by the polarizing Mach-Zehnder interferometer (pMZi). The detection of the changed polarization states of the incident light due to reflection on the sample surfaces led to a set of unique characteristics describing a thin-film substrate system in terms of ellipsometric parameters ψ and Δ. SiO₂ thin-films were chosen to study because of their well known characteristics. The accuracy of measurements was confirmed by comparisons to calculated values derived from Fresnel's equations and a standard instrument. The results clearly reveal a feasibility of using the rotating linearly polarized light produced by pMZi for a non-destructive characterization of the thin-film system.

We report an 1×3 optical drop splitter (ODS) based on a self-collimation ring resonator (SCRR) in a rod-type silicon photonic crystal. The proposed 1×3 ODS consists of four beam splitters which are formed by changing the radius of one row of silicon rods. When the self-collimated light with resonance frequency is launched into the ODS, the light beam can be split into three parts come out from three drop ports while no light coming out from the through port. The splitting ratio of the three drop beams can be controlled by tuning the radii of the beam splitters. The FDTD method is employed to calculate the transmission of the 1×3 ODS. For the drop wavelength of 1550 nm, the free spectral range is 28.7 nm, which almost covers the whole optical communication C-band window. This 1×3 ODS may have applications in photonic integrated circuits.

A novel CMOS-compatible thermal compensator which can compensate most of silicon photonic integrated devices with the positive thermal-optical effect was demonstrated using a modified asymmetric Mach-Zender-Interferometer. Furthermore, an athermal waveguide was designed using the demonstrated thermal compensator to compensate the conventional waveguide with the positive thermal-optical effect. Based on simulations, the temperature dependence of the athermal compensated waveguide is stable within the temperature range of 25-52 °C and the temperature range can be largely extended through optimizing the structure of the thermal compensator. In addition, the different length of conventional waveguide can be compensated by adjusting some parameters.

In this paper we describe two silicon based optical modulators that have been fabricated as part of two projects in which the Surrey group is involved, the "UK Silicon Photonics project" funded by the UK Engineering and Physical Sciences Research Council (EPSRC), and the European "HELIOS" project funded by the European Union. The modulators exploit the carrier depletion effect in MZI structures, but have different advantages and disadvantages. One has a performance that is close to polarisation independence, whilst the other demonstrates a very high extinction ratio for a 40Gb/s silicon modulator. Both are shown to operate at 40Gb/s.

As a result of the low modulation efficiency of carrier-depletion Mach-Zehnder silicon optical modulator, it always needs a high voltage around 6 V, which is very difficult to supply in an integrated high-speed CMOS chip. We demonstrate a carrier-depletion Mach-Zehnder silicon optical modulator which works at a low voltage. Its coplanar waveguide electrode is carefully designed to make sure the electrical wave loss along the device is low. The device operates well at a data rate of 12.5 Gb/s, whose phase-shifter length is 2 mm. Voltages with the swinging amplitudes being 1 V and 2 V are applied to the device with the reverse bias voltages of 0.5 V and 0.8 V. The extinction ratios are 7.67 and 12.79 dB respectively.

Broad gain lasers attract much interest due to the practical gas sensing applications. A step well structure with double optical transitions is implemented in the active region of injectorless quantum-cascade lasers (QCLs) to achieve extended gain bandwidth. The step well is constructed by a "short period superlattice" which provides an equivalent GaInAlAs alloy quantum step well in each active module. The fabricated devices show an ultrabroadband gain spectrum of 480 cm^-1 (4 μm) at room temperature in pulsed mode. The laser threshold current density is as low as 1.1 kA/cm² which is the lowest among the broad gain QCLs emitting at similar wavelengths and the slope efficiency is 1.6 W/A at room temperature.

For stimulates great developments in high-speed and high-capacity Cloud Computing Technologies (CCT) systems in the future. The all-optical logic gate based on planar photonic crystal (PPC) waveguide is a promising technology. We design an all-optical AND gate in PPC, as an ultracompact component for planar lightwave circuit integration with suitable choice of parameters, perform this task. The PPC waveguides are composed of circular dielectric rods set in two-dimensional triangular lattice. To realize the AND logic function, as predicted using 2D finite-difference time-domain simulations. The combination of the ring and line defect coupler waveguides forms the device. On the basis of our simulations, we found that the optimized scheme maximizes the power transmission above 80% at a wavelength of 1.55 um. Besides, this device can apply to all-optical Arithmetic Logic Unit (ALU) in all-optical computing and potentially applicable for photonic integrated circuits (PICs) in the future.

We proposed a three-wavelength multiplexer/demultiplexer based on the characteristics of resonant coupling between photonic crystal ring resonator (PCRR) and cavity. The structure composed of one PCRR and three cavities. The numerical results obtained by the finite-different time-domain (FTDT) method show that it can realize the demultiplexing of three wavelengths, i.e. 1430nm, 1490nm and 1550nm only by modulating the radius of the cavities. The designed device not only has a compact size with 12μm×11μm but also a high efficiency, may have potential applications in the integrated optics fields.

We design a highly efficient channel drop filter (CDF) with only one channel drop micro-cavity based on photonic crystal (PC) one-way waveguide. By means of the new nature of waveguide-cavity interaction, over 95% channel drop efficiency can be realized in the structure. Some multichannel drop filters with high drop efficiencies are also engineered based on such the structure. These numerical results are all calculated by using the finite element method (FEM), which agrees well with the theoretical analysis result.

A ring-cavity synchronously-pumped optical parametric oscillator was investigated, which was pumped by a self-mode-locked Ti:sapphire laser. A periodically poled KTiOPO₄ crystal was used in the oscillator, and the parametric operation was obtained. The wavelength of the signal wave covered from 1000 nm to 1500 nm. The signal wave was successfully frequency doubled by inserting a nonlinear BBO crystal in the cavity. The wavelength of second harmonic could be tuned from 550 nm to 650 nm freely by cavity-length tuning. The loss of the cavity and the threshold of the pump power, a thin glass substrate is inserted into the cavity to couple output the light, then the output power is measured for varying pump power, based on the measurement the loss in the cavity was discussed. Furthermore, the characteristic of output pulses is also measured.

A dual-depletion-region lumped electroabsorption modulator (DDR-LEAM) based on InP at 1550nm is designed and fabricated. The measurement results reveal that the dual depletion region structure can reduce the device capacitance significantly without any degradation of extinction ratio. The simulation results show that the highly doped charge layer can concentrate almost all of the external applied voltage in MQW region and thus contribute to the identical extinction ratio curves. The expected 3-dB bandwidth of the DDR-LEAMs using an equivalent circuit model is more than twice lager than that of the conventional LEAM.

In this work, the slow light modes of the polyatomic photonic crystal (PhC) which has multiple different holes in the smallest unit cell are investigated. The slow light waveguide with nearly constant group index over large bandwidth is achieved using this new photonic crystal geometry based on square lattice. The feasibility of controlling the dispersion relation through subtle structural modification is also investigated.

Scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM) both are capable of mapping the 2-demensional carrier distribution in semiconductor device structures, which is essential in determining their electrical and optoelectronic performances. In this work, cross-sectional SCM^1,2 is used to study the InGaAs/InP P-i-N junctions prepared by area-selective p-type diffusion. The diffusion lengths in the depth as well as the lateral directions are obtained for junctions under different window sizes in mask, which imply that narrow windows may result in shallow p-n junctions. The analysis is beneficial to design and fabricate focal plane array of near infrared photodetectors with high duty-cycle and quantum efficiency. On the other hand, SSRM provides unparalleled spatial resolution (<10 nm) in electrical characterization³ that is demanded for studying low-dimensional structures. However, to derive the carrier density from the measured local conductance in individual quantum structures, reliable model for SSRM is necessary but still not well established. Based on the carrier concentration related transport mechanisms, i.e. thermionic emission and thermionic field emission^4,5, we developed a numerical model for the tip-sample Schottky contact⁴. The calculation is confronted with SSRM study on the dose-calibrated quantum wells (QWs).

In this paper, we present a multi quantum dot (MQD) white light emitting Diode structure. In order to construct, white light spectrum, we use different quantum dot layers to generate blue, green and red colors. These layers contain quantum dots with active layers of In_(x)Ga_(1-x)N with GaN barrier. We investigate that these three colors is theoretically are extracted from each set of quantum dots, then these colors are combined with a desired intensities together and finally a light near white light will be created. Through adjusting material composition and quantum dot sizes, the white color quality can be improved. Piezoelectric and spontaneous polarization internal field are entered in our calculations.

An ultraviolet photosensor based on ZnO nanoplates has been successfully fabricated. ZnO nanoplates was synthesized by sonochemical method and coated on Cu interdigitated electrodes. The method is simple, rapid and applicable to research prototypes for further studies of ZnO nanoplates for nano-device applications. The current-voltage (I-V) characteristics show linear behavior and the photosensor exhibits a response of ~803mA/W for UV light under 15 V bias. Compared to other nano detectors, the fabricated detector shows fast photo response with a rise time of 150 ms and fall time of 50 ms compared to the other nanomaterial based photosensors.

We propose an ultrahigh-speed all-optical wavelength conversion for polarization-shift-keying (PolSK) signal, based on parallel dual-pump four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). A comprehensive broad-band dynamic model of this kind of all-optical wavelength converter is developed. By numerical simulation, using the broad-band dynamic model, the effects of input waves powers and wavelengths on the output performance of wavelength conversion for PolSK signal are theoretically investigated in detail. This scheme is suitable for wide wavelength range of input PolSK signal. It is simple, compact, and feasible for ultrahigh-speed operation.

We proposed a simultaneous three-wavelength conversion based on the cross-gain modulation (XGM) in the multi-wavelength semiconductor fiber ring laser (SFRL). It is easily implemented owing to the simple structure. Furthermore, it has realized multi-channel wavelength conversion, which reduces the cost of network expansion. A comprehensive broadband dynamic model is presented. By numerical simulation, the proposed multi-wavelength conversion is theoretically realized using the broadband dynamic model. Moreover, the dependences of conversion efficiency and extinction ratio on the input signal power, signal wavelength and injection current are investigated in detail.

A hybrid-integrated coherent receiver module has been achieved using flip-chip bonding technology, consisting of a silica-based 90°-hybrid planar lightwave circuit (PLC) platform, a spot-size converter integrated waveguide photodiode (SSC-WG-PD), and a dual-channel transimpedance amplifier (TIA). The receiver module shows error-free operation up to 40Gb/s and OSNR sensitivity of 11.5 dB for BER = 10^-3 at 25 Gb/s.

Nanosized colloidal gold was prepared by the reduction of chloroauric acid with trisodium citrate in aqueous solution with microwave heating method. The diameters of gold nanoparticles were from 13 to 70 nm with the ratio of the trisodium citrate and chloroauric acid. With rhodamine 6G (R6G) as the detection molecules, the SERS properties of gold colloid were studied. Experimental results show that the gold colloids with 50-60nm particle diameters are excellent SERS substrates and sodium chloride (NaCl) can improve gold colloid's surface-enhancement effect.

The paper considers results of designing and modeling analogue-digital converters (ADC) based on current mirrors for the optical systems and neural networks with parallel inputs-outputs. Such ADC, named us multichannel analog-todigital converters based on current mirrors (M ADC CM). Compared with usual converters, for example, reading, a bitby- bit equilibration, and so forth, have a number of advantages: high speed and reliability, simplicity, small power consumption, the big degree of integration in linear and matrix structures. The considered aspects of designing of M_ADC CM in binary codes. Base digit cells (ABC) of such M_ADC CM, series-pipelined are connected in structures, consist from 20-30 CMOS the transistors, one photodiode, have low (1,5-3,5) supply voltage, work in current modes with the maximum values of currents (10-40)μA. Therefore such new principles of realization high-speed low-discharge M_ADC CM have allowed, as have shown modeling experiments, to reach time of transformation less than 20-30 nS at 5-6 bits of a binary code and the general power 1-5 mW. The quantity easily cascadable ABC depends on wordlength ADC, and makes n, and provides quantity of levels of quantization equal N=2ⁿ. Such simple enough on structure M ADC CM, having low power consumption ≤ 3 ÷ 5mW, supply voltage (3-7)V, is provided at the same time with good dynamic characteristics (frequency of digitization even for 1,5μm or 0,35 μm- CMOS-technologies has made 40 MHz, and can be increased 10 times) and accuracy (Δ_quantization 156,25nA for I _max10μA) characteristics is show. The range can be transformed optical signals, taking into account sensitivity of modern photodetectors makes 20-200 μW in such ADC. M_ADC CM open new prospects for realization linear and matrix (with picture operands) micro photoelectronic structures which are necessary for neural networks, digital optoelectronic processors, neurofuzzy controllers, and so forth.

A novel scheme to realize all-optical logic gates is proposed bases on nonlinear polarization rotation (NPR) in high nonlinear fiber (HNLF). Two optical signals A and B with return-to-zero data format are injected into the HNLF together with a continuous wave C. Thanks to the optical power variation in HNLF, nonlinear birefringence will be induced between the two polarization axes. Thus it results in the nonlinear polarization rotation of the lightwave in the HNLF. Both the optical signal and continuous wave are filtered out at the output of HNLF using optical band-pass filter. By adjusting the optical power and polarization of the optical signal as well as the polarization of the polarizer with respect to the polarization of optical signal/continuous wave, multiple all-optical logic gates can be realized. Theoretical analysis of the simultaneously realization of the multiple optical logic gates based on NPR in HNLF is provided. And we demonstrated the feasibility of the scheme by realizing all optical "and", "not", "nxor", "A•B", "A•B ", half-adder and half-subtracter at 10Gb/s operation.

A high frequency optoelectronic oscillator (OEO) using only low frequency optical and microwave devices is attractive as it provides a low cost and high quality solution at the same time. In this paper, a novel OEO scheme is reported. The proposed optoelectronic oscillator includes a 5GHz directly modulated DFB laser, an optical circulator, a 10GHz photodetector, a 10GHz RF amplifier, and a bandpass RF filter with a central frequency at 5GHz. The OEO oscillates at the 5GHz and with a continuous wave injected into the directly modulated DFB laser, higher harmonics will be generated. The harmonic order can be controlled by the frequency difference between the free running DFB laser and injection lightwave. An optical domain combined dual-loop configuration with polarization-beam splitter and a polarization-beam combiner is employed to suppress the sidemodes in each single loop. Experiment results are proposed to verify the scheme, in which 40GHz microwave is obtained.

The effect of growth temperature on InAs QDs grown by metal-organic chemical vapor deposition (MOCVD) was investigated in detail. Growth temperature affects InAs QDs in three ways, including the reconstruction mode of new InAs crystal faces, the migration length of adatoms, band gaps of InAs QDs, and the interaction among three aspects was studied. The variation of density, size and wavelength was experimentally demonstrated. The high density of 5.2×10¹⁰cm^-2 was obtained. The room temperature wavelength of InAs/GaAs QDs using GaAs as capping layer reached 1240nm.

We have fabricated strain-reduced InAs quantum dots (QDs) by boron incorporation grown on GaAs(100) substrate. The size of uncapped InAs QDs was increased with boron incorporation. The effect of boron on the PL spectra of InAs QDs capped by an InGaAs strain-reducing layer wasn't obvious. However, when boron atoms were incorporated in InAs QDs capped by a GaAs overgrown layer, the PL intensity was strongly enhanced, and the PL peak shifted towards a longer wavelength. It was found that the incorporation of boron atoms within the InAs QDs could drastically reduce the In/Ga intermixing effects during capping coverage.

Analysis of light field distribution within a dual-absorption RCE p-i-n photodetector has been performed. A formula for the field distribution inside the cavity is derived. This formula is derived from the continuity equations, and employed to evaluate the frequency response of the dual-absorption RCE photodetector. This photodetector has been optimized for high-speed applications. The optimized structure shows a 3dB bandwidth of 20 GB with intrinsic absorption region to be 400nm, as well as effective illumination area and peak quantum efficiency to be 900 μm² and 92%, respectively.

This paper presents the design and analysis of a novel resonant cavity enhanced photodetector which is realized by utilizing concentric circular subwavelength gratings (CC-SWGs) as reflective mirrors. The CC-SWG proposed here can achieve a reflectivity of higher than 99% within a broad wavelength range from 1.37 to 1.63 μm. The calculated peak quantum efficiency of the designed photodetector can achieve 90% at 1.55 μm.

To characterize and predict the dynamics of the nonlinear polarization rotation (NPR) in semiconductor optical amplifiers (SOA) an experimental method based on the frequency response technique and a model based on the density matrix and effective index formalisms are presented. Particularly, the frequency response of the NPR is obtained by determining, for each studied frequency, the angular displacement, at the Poincare Sphere, that separates the initial and final points of the polarization evolution of the output beam.

We investigate theoretically the effect of two-dimensional photonic crystal (PC) defect waveguide parameters embedded into vertical-cavity surface-emitting laser (VCSEL) on static operation of PC-VCSEL like spatial hole burning (SHB) and temperature of active region. In structures with larger pitch of PC holes SHB occurs dramatically and temperature increases in active region. In large hole diameter to pitch ratio, SHB has a little effect and temperature is decreased in active region.