This PDF file contains the front matter associated with SPIE Proceedings Volume 8333, including the Title Page, Copyright information, Table of Contents, Introduction, and the Symposium and Conference Committees listing.

We propose a novel reconfigurable optical en/decoder to generate and recognize two-dimensional (2-D) optical codes for coherent optical-code-division-multiple-access (OCDMA) application. The proposed device is based on cascaded coupled micro-ring reflectors, which can enable simultaneous tuning of the fast wavelength hopping and spectral phase encoding code patterns. The coding performance is verified by simulation.

We experimentally demonstrate continuously tunable optical time delay and advance using coupling-modulated microring resonators (CMR) with a 15-μm radius. By modulating the coupling coefficient through thermo-optical effect based on micro-heater, the coupling state of the microring is flexibly controlled; as a result, a large dynamic time tuning range (from time advance to delay) is achieved. The CMR device based on SOI is fabricated with commercial 0.18-μm CMOS technology. A novel micro-heater structure was firstly used to thermally tune the coupling state of the micoring. Pulse delay and advance from -15 ps to 85 ps is experimentally realized.

Optical network-on-chips (ONoCs) will play an important role for optical interconnects in the next generation chip multiprocessors (CMPs). Recent advances in silicon integrated photonics make it viable to develop ONoCs using the standard CMOS process. This paper will introduce our work on cascaded-multiring-based tunable filters and ring-based integrated switchable wavelength routers.

Improved Extinction Ratio of 25 dB was demonstrated in silicon based optical modulators on CMOS platform in China. The measurement results agree with the simulation, followed by a discussion about the effects of both propagation loss in Mach-Zehnder arms and power ratio at beam splitters and combiners. The analyses indicate that many considerations have to be taken into design and development of the compatible fabrication of these integrated silicon photonics, especially for the improved extinction ratio of optical modulators. In this summary, we propose the integrated optical modulators in SOI by use of the compatible CMOS processes under the modern CMOS foundry in Chinese homeland. And the measured results were shown, the fast response modulator with the data transmission rate of 10 Gbps.

We demonstrate a novel scheme to generate ultra wideband (UWB) doublet pulses by inputting a dark return-to-zero (RZ) signal into a fiber delay interferometer (FDI). When a dark RZ pulse train with a repetition rate of 0.625 GHz and a pulse width of 120 ps was inputted into a FDI with a free spectrum range (FSR) of 0.16 nm (~20 GHz, according time delay is ~50 ps) and an extinction ratio (ER) of 9 dB, by adjusting the control temperature of the FDI, the phase difference of the input light on the both fiber arms of the FDI is changed and controlled, UWB doublet pulse is directly generated at the output port of the FDI. The system parameters effects on the output signal were also discussed. Moreover, we numerically demonstrated that, by carefully optimizing system parameters, UWB quadruplet pulses also can be generated. This scheme has some distinct advantages including easy integration, convenient tuning, good stability, and so on. Presented method also accords with the general features in future applied UWB system, namely, single optical source input, simple configuration and passive device.

Based on DWDM and EDFA technology, 7.5 Gbps free space laser communication demonstration system was developed. Experiments of 7.5 Gbps 40km free space laser communication were completed in Qinghai lake Qinghai province on the Aug. 2010.Error free communication was achieved at the speed of 155 Mbps, and 10-7 BER was achieved at the speed of 2.5Gbps, 5Gbps and 7.5Gbps test with BER of 10^-8~10^-7 and 10^-7 ~ 10^-6 were completed. Laser atmospheric propagation experiments were conducted and analyzed.

Low timing jitter, sub picoseconds pulse source at 1.55 μm is demonstrated by integrating a fast saturable absorber mirror (SESAM) with an optically-pumped mode-locked vertical-extended-cavity-surface emitting laser (ML-VECSEL). In such a soliton-like pulse-shaping mechanism, short pulse generation requires to control the group delay dispersion (GDD) in the cavity in order to balance the nonlinear phase shift induced by strong semiconductor gain and absorber saturation. By using selective etching technology, we controlled the SESAM optical cavity by varying from a resonant to anti-resonant configuration (which corresponds to a GDD variation from -2000fs2 to +500fs2 at 1.55 μm) in the passive mode-locking cavity. Using the same VECSEL chip, we observed that the mode-locked pulse duration could be reduced from several ps to less than one ps with a resonance managed SESAM.

All-optical signal processing offers the prospect of realizing high sampling bandwidth and overcoming many of the limitations of electronics. This work introduces the use of planar Bragg gratings in all-optical signal processing. The key fabrication technique is direct grating writing (DGW). One significant advantage of the DGW system is the small spot size of the focused laser beam used to inscribe the waveguide and grating. Rather than using the wide area exposure such as that from a phase mask, DGW uses a direct UV laser spot such that the dimensions of the UV induced structure are determined by the focal spot size. For complex grating engineering this feature is superior to the conventional phase mask techniques, allowing accurate control of the chirp, phase shifts, apodisation and other parameters to produce intricate optical response.

We propose and demonstrate a novel elliptical microdisk resonator which enables single-mode operation with high quality (Q) factor. Such elliptical microdisk resonators with pedestal, which consist of plenty of smoothly changing bends with modified curvature radii, can easily achieve single-mode operation due to selective losses introduced by mode transmission mismatches and small curvature radii portion inside the elliptical microdisks. We fabricated the devices on silicon-on-insulator (SOI) platform. Single-mode resonance with high quality factor (Q) of ~105 was experimentally realized. Besides, the proposed elliptical microdisk provides larger coupling strength compared to normal circular microdisk, and hence enables critical coupling with easy-to-fabricate gaps.

The combined laser model based on transmission line laser mode (TLLM) is extended to investigate intensity modulation (IM) response and frequency modulation (FM) response of SGDBR lasers in this paper. While carrier-depended refraction index, spontaneous emission noise and their coupling are included in the consequent dynamic frequency shift and intensity fluctuation can reflect dynamics of SGDBR lasers in more real circumstances. Simulation results indicate that direct modulation bandwidth increases as bias current increases in IM. Frequency chirp in small signal IM and the fluctuation of output optical power in FM are also discussed.

We present a novel micrometer-sized intensity modulator based on a silicon-polymer hybrid plasmonic waveguide. The field enhancement in the low-index high-nonlinear polymer layer provides a nano-scale optical confinement and a fast optical modulation speed. After applying a voltage, the surface plasmon waves experience different phase delays, resulting in an intensity variation at the output waveguide. Due to its small capacitance and parasitic resistance, the RC delay time is <6 ps, corresponding to a modulation bandwidth of >40 GHz. The intensity modulator can find potential applications in optical telecommunication and interconnect.

We systematically investigate the optical effects and the optical functions of coupling-modulated microring resonators (CMR) based on interleaved p-n junctions. The optical effect of coupling-induced frequency shifts (CIFS) is firstly observed experimentally. Due to the CIFS and thermal-optical effect, the resonance spacing is tuned as large as 0.182 nm (corresponding to 22.8 GHz), the extinction ratio is continuously modulated between 0 dB to as large as 35 dB.

Optical waveguide directional couplers can perform some very useful functions in a variety of integrated optical applications, especially when the branch arm incorporates gain. In this paper, the performance of three-dimensional active optical waveguide directional coupler is analyzed by finite-difference beam propagation method (FD-BPM). The paper analyses the impact of normalized gain difference and normalized phase difference on optical power transfer characteristics. The transmission characteristics of three-dimensional active waveguide coupler in phase matching and mismatching are discussed in detail. In addition, the influence of geometric parameters of three-dimensional waveguide coupler on the transmission characteristics is analyzed. The result of above analysis can be helpful for optimizing the active coupler designing.

We study numerically the tunable all-optical pulse compression induced by stimulated Brillouin scattering (SBS) double gain lines for Gaussian, super-Gaussian, and square shaped input pulses in optical fibers. We consider that the steepness of input pulse edges has an influence on the distortion and the broadening or compression factor of output pulses through the SBS-double-gain-line systems. For a Gaussian input pulse the distortion is relatively lower with the pulse compression ratio is only 0.75 in minimum. For a square input pulse the compression ratio can reach to 0.29 in minimum, but the distortion is highest.

Graphene, two-dimensional carbon crystal with only one atom thickness, provides a general platform for nanoscale even atomic scale optoelectronics and photonics. Graphene has many advantages for optoelectronics such as high conductivity, high electronic mobility, flexibility and transparency. However, graphene also has disadvantages such as low light absorption which are unfavorable for optoelectronic devices. On the other hand, many natural photonic systems provide wonderful solution to enhance light absorption for solar energy harvesting and conversion, such as chlorophyll in green plants. Herein, learning from nature, we described bioinspired photocatalytic solar-driven water splitting, sensitized solar cells and ultraviolet optoelectronic sensors enabled by introducing photosensitive semiconductor nanocrystal antenna to graphene for constructing a series of graphene/nanocrystal nanoassemblies. We have demonstrated that high performance optoelectronic devices can come true with the introducing of photosensitive nanocrystal antenna elements.

Aim: Organic, biological materials and soft matters with optoelectronic donors and acceptors are postulated to be novel optoelectronic device materials. Methods: Molecular self-assemblies of nanomedicine crystals are employed by inelastic electron tunneling interaction force, which is a quantum force to make basic units of organic, biological and soft matter with optoelectronic donors and acceptors to be enlarged from nanometers to micrometers on silicon chips. Results: Self-assembled topographic structures and corresponding conducting with kondo effects and photoluminescence properties of self-assembled nanomedicine crystal building blocks are demonstrated by conducting atomic force microscopy (C-AFM) images and current-voltage curves, and laser micro- photoluminescence (PL) spectra. By contrast to top-down processing, the bottom-up processing of molecular self-assembly is low cost on large scale industrial manufacturing. Conclusion: The self-assembled nanomedicine crystal building blocks with optoelectronic donors and acceptors are candidates of novel optoelectronic device materials to be in the emerging discipline of information technology (IT) in its broadest sense, i.e. bioelectronics & biosensors, optoelectronic devices, data storage devices; simple to complex quantum entanglements and superposition for quantum bits computing, a novel strategy for 2020 IT and beyond.

We present a kind of depletion-mode silicon modulators based on cascade interleaved PN junctions, which simultaneously provide high modulation efficiency and large modulation bandwidth. The interfaces of the PN junctions are vertical to the waveguide's propagation direction and tolerant with ± 150nm junction misalignment on the cost of little degradation on the modulation efficiency. The device was fabricated with standard 0.18μm CMOS process, and provides a VπLπ < 1V • cm and an intrinsic bandwidth 39GHz. Over 10GHz electro-optical modulation bandwidth of the device was experimentally obtained. High speed non-return-zero modulation with a bit rate up to 25Gbit/s was finally demonstrated.

The 650nm oxide-confined RCLEDs (resonant-cavity light-emitting diodes) have been fabricated with different oxide aperture diameters. The oxide apertures, which could apply confinement of both the carrier distribution and the optical field, are created by lateral selective wet oxidation of AlAs layer in the p-DBR (distributed Bragg reflectors). All samples have the same diameter 80μm of the emission window defined by the circular electrodes, while their current apertures are defined by the oxidation apertures ranged from 90μm to 130μm, larger than the emission window. The maximum optical power is 1.909mW. The electrical and optical properties are systematically discussed for different oxide apertures. The greater voltage at 20mA is attained for smaller oxide-aperture devices as smaller oxide-aperture devices have greater series resistance due to the oxide layer. The maximum output power is reached rapidly for smaller oxide-aperture devices since smaller oxide-aperture devices have larger current density at the same current. The maximum output power of smaller oxideaperture devices is lower than that of larger oxide-aperture devices. It is because that larger current density and greater series resistance could lead to greater Joule heat, which results in more injected electrons relax their energy by the way of nonradiation.

A novel scheme is proposed to obviously improve the amplified gain, gain flatness and bandwidth characteristics of FOPA by applying a cascaded fiber structure. The basic structure of the cascaded fiber optical parametric amplifier (CFOPA) is introduced. Then, the expression of signals pass gain characteristic is obtained by utilizing a set of coupled equations. The gain, bandwidth and gain flatness characteristics of the CFOPA with the different parameters of DCF, such as fiber length l^/, dispersion slope dD//dλ, and so on, are theoretical analyzed and optimized. Furthermore, simulation analysis is applied to verify the theoretical results by using Optisystem 7.0 software. Although, there are a few deviations between the simulation and the theoretical results, the simulation results effectively demonstrate the validity and feasibility of the theoretical analysis.

We investigated photonic crystal vertical cavity surface emitting laser with elliptical air holes,which can produce a circular beam with standard substrates in a relatively easy fabrication process.Because of the elliptical air holes,the mutually perpendicular directions of photonic crystal have different effective index,the photonic crystal cavity has highly birefringent.Normal photonic crystal VCSELs send single mode laser,and the basic mode was orthogonal double degennerate state.The polarized direction could change easily.If we used elliptical air holes to break the symmetric structure of photonic crystal,because of the highly birefringent,one of polarization modes was frustrated,only one polarized mode could transmit.We introduced elliptical air holes in the top mirror and get polarization controlled laser.The spacing between air holes was 4μm and the dimentions of the elliptical air holes were 2.0μm×1.4μm.The polarization controlled photonic crystal vertical-cavity surface-emitting laser shows side mode suppression ratio(SMSR) over 30dB,and controlled the polarization of laser in one direction.

Three different aperture diameters (6μm,8μm,10μm) of proton implantation vertical cavity surface emitting lasers (VCSEL) are fabricated by two different group energy bombardment, where the epitaxial structure is designed lasing at 850nm. The injection energy is 300kev, 230kev and 330kev, 250kev, 160kev respectively, in order to confine the current path. To avoid channel effect while injecting and to make the actual fabrication process behind convenient, 5000Å SiO₂ was deposited on the surface of the wafer. Photoresist and Au are used as the mask to protect the lasing area against bombardment, respectively. When the aperture diameters is 10μm and under the two times bombardment, the output power of continuously at room temperature is reached at 2.4mw, while the same aperture diameters under three times bombardment is only 0.5mw. Further analysis indicates that the distance of injection peak value from the active region is a critical parameter to determine the output power.

We have analyzed transverse mode characteristics of 850-nm oxide-confined vertical-cavity surface-emitting laser (VCSEL) with shallow surface relief (SR) structure by finite-difference time-domain (FDTD) method. We have used FDTD solution software to complete the full 3D simulations, which costs us about 24 hours for every structure. The ring form SR structure has been located in the central of the topmost DBR, and the depth is 1/4 optical wavelength, which can suppress the higher mode from emitting to the maximum extent. We have simulated different inner diameter of the ring form structures on 10-μm oxide-confined VCSELs, and compared the transverse mode characteristics with that of ordinary VCSEL. Finally find the structure can effectively decrease far-field divergent and improve transverse mode performance. The most suitable inner diameter is 6.5-μm, and the full-width half-maximum of the far-field divergent angle is 5.5°, which provides guideline for actual device fabrication.

Single fiber laser can reach kilowatt level output. Higher power output is limited by nonlinear effect inside the fiber, heat deposition and pump power. Spectral beam combining of multiple laser beams with offset wavelengths into a single near-diffraction-limited beam is an effective solution to increasing energy brightness and scaling output power of high-power lasers. The loss factors of effect on the diffraction efficiency of the gratings are discussed. Design principles and technical approach for spectral beam combining (SBC) of two channels and three channels by reflecting volume Bragg grating are investigated. Two and three channels SBC are numerically analyzed when the input beam divergence is 0.06mrad. The results show the SBC efficiencies are 98.65% and 97.57% when the spectral width is 0.1nm, and the efficiencies are 92.16% and 88.98% when the spectral width is 0.3nm, respectively.

A new photochromic diarylethene compound, 1-(2,4-dimethyl-5-thiazolyl)-2-[5-(3- pyridine)-2-methyl-3-thienyl] perfluorocyclopentene(1a) was synthesized. its photochromic and fluorescent properties have been investigated in detail. While, fluorescence properties in hexane and PMMA have also been discussed. The results of the research demonstrated that it has shown good photochromic behavior and relatively strong fluorescence in hexane solution and in PMMA at room temperature. At last, using this dithienylethene as recording medium, photon-mode holographic optical storage was performed successfully.

A novel unsymmetrical diarylethene derivative 1-(2-methylphenyl)-2-{2-methyl-5-[2-( 1,3-dioxolane)]-3-thienyl}perfluorocyclopentene(1a) was successfully synthesized. The properties of the compound, including photochromic and fluorescence properties of the diarylethene were also investigated systematically. Diarylethene 1a changed the color from colorless to red upon irradiation with 297 nm UV light, in which absorption maxima were observed at 523 nm in hexane and at 528 nm in PMMA film, respectively. In hexane solution, the open-ring isomer of the diarylethene 1 exhibited relatively fluorescence at 393 nm when excited at 326 nm.

A symmetrical diarylethene bearing two differerent substituents was synthesized successfully, its photochromic properties in solution and PMMA film were investigated in detail, respectively. In addition, the diarylethene as rewritable optical recording media was also performed successfully.

Photovoltaic is a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect. Photovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material. Due to the growing demand for renewable energy sources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in recent years. Solar photovoltaics are growing rapidly, albeit from a small base, to a total global capacity of 40,000 MW at the end of 2010. More than 100 countries use solar photovoltaics. Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaic has declined steadily since the first solar cells were manufactured. Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity; have supported solar photovoltaics installations in many countries. However, the power that generated by solar photovoltaics is affected by the weather and other natural factors dramatically. To predict the photovoltaic energy accurately is of importance for the entire power intelligent dispatch in order to reduce the energy dissipation and maintain the security of power grid. In this paper, we have proposed a big data system--the Solar Photovoltaic Power Forecasting System, called SPPFS to calculate and predict the power according the real-time conditions. In this system, we utilized the distributed mixed database to speed up the rate of collecting, storing and analysis the meteorological data. In order to improve the accuracy of power prediction, the given neural network algorithm has been imported into SPPFS.By adopting abundant experiments, we shows that the framework can provide higher forecast accuracy-error rate less than 15% and obtain low latency of computing by deploying the mixed distributed database architecture for solar-generated electricity.

Slowing down the light in Slotted Photonic Crystals Waveguides (SPCW) offers strong opportunities for all-optical signal processing and non linear optics by dramatically increasing the local electromagnetic energy density in the low index material. We introduce a novel design of wide SPCW, where the slot is structured as a comb. We show that structuring the slot in a SPCW allows performing proper dispersion engineering in order to achieve very low group velocities over a few nanometers. This hybrid structure of SPCW offers possibilities to realize devices requiring strong interactions between light and an optically non-linear low index material by providing an ultra-high optical density while easing the filling of the slot due to its large width. We will present the methodology of the dispersion engineering and we will investigate later the losses and the non linear properties by FDTD analysis and experimental realization.

To reduce of setup time of communication link and increase of acquisition probability for free-space optical communication, the GPS technology is applied and the unidirectional acquisition experiment system, controlled by user interface, is established with the control core of TMS320F2812. the coordinate from GPS is input to user interface by manual, formed into the horizontal- and vertical- Angle to adjust based on the GPS coordinate and sent to F2812 for driving of two-dimension platform to finish initial acquisition. The acquisition experiment is done many times and the result show that the quick and high probability acquisition could be achieved based on GPS technology.

The adaptive optics(AO) technology is adopted in the demo experiment of indoor space laser communication system. In transmit terminal, 650nm beacon and 1550nm signal beam with OOK modulation propagate through atmosphere turbulence simulator which simulate the laser's propagation in real atmosphere conditions. The AO system corrects real time wave-front information. In received terminal, signal intensity is collected and the bit error rate(BER) is recorded. Experiment data is obtained in different status of the AO system. Combined with signal beam wave-front reconstructed and image quality of far-field laser spot, results show that the received average power of communication system increases when using the AO system to correct low-order aberration. Also it rejects signal fading and makes the BER lower.

The paper introduces a kind of super relative aperture condenser which has the strcuture of spherical Fresnel surface with catadioptric projection optical system, it would improve the condensing capacity and light efficiency substantially. The condenser is composed of two sections with a center and an outer ring, the center region adopted the basic structure of the Fresnel lens with the Fresnel of laplace domain continuous curve transmission type, and the outer structure which achieve light collimating or focusing by total reflection is stepped. The paperstudies the parameter and alforithm of this catadioptric dual-zone Fresnel condenser and gives the surface data of total reflection region. Based on the method of establishing the entity model, we design a set of lens with the relative aperture F=0.3, simulate the condensing ability of the lens by the simulation software, and verify that the lens have a very good effect on focusing.

A butt-coupled low dispersion slow light photonic crystal waveguide has been proposed in this paper. It is comprised of two types of photonic crystal waveguides which have opposite dispersion curve. These two types of photonic crystal waveguides have been solely adjusted the radius of air-holes rather than change its position. Based upon our analysis, the average group index achieves 35 with Δ λ=6nm and this scope can be enlarged by fine adjustment. Finite-different timedomain method has been adopted to execute the simulation and the result demonstrates that the pulse has been modified when it propagates in this butt-coupled photonic crystal waveguide.

This paper presents a novel all-optical in-band optical signal-to-noise (OSNR) monitor. The monitoring ability arises from the power transfer function (PTF) provided by un-phase-matched four-wave mixing (FWM). A much higher output contrast compared to formal methods can be obtained at a much lower required power. Numerical simulations are then used to quantify the sensitivity enhancement for signals with different modulation formats which show that the monitoring sensitivity can be greatly improved by more than 10 dB for NRZ, CSRZ, RZ modulation formats while the required power can be reduced by about 3 dB.

We proposed and theoretically simulated an optically switchable and tunable ultrawideband (UWB) doublet generator based on wavelength conversion in a semiconductor optical amplifier (SOA), and optical tunable delay in optical delay lines (ODLs). The system is optically switchable in pulse polarity, and tunable in both pulsewidth and radio frequency (RF) spectrum.

We investigate the nonlinear characteristics of the Mach-Zehnder (MZ) intensity modulator using based on Bessel series expansion. The method we used provides the easy characterization of the harmonic components of an MZ intensity modulator. Theoretical analysis results are agreeable with those obtained in the experiment. Compared to the traditional methods, this method can analyse the operating characteristics of the MZ intensity modulator without executing a complicated experiment. It can not only be used to characterize harmonic component of MZ intensity modulator with high accuracy and fast calculation, but also can be extended to analyze the nonlinear distortion of the analogue signal modulation.

Based on the modified coupled-wave theory of single volume grating and matrix theory, the time-domain diffraction of multi-layer reflection volume holographic gratings recorded in photorefractive LiNbO₃ crystals are theoretically studied when they are illuminated by ultrashort pulse laser. Study shows that the waveforms of the diffracted pulses depend on the readout pulse duration, grating periods, refractive index modulation of the grating, thickness of the buffer layers and gating layers. The diffracted waveforms and intensity can be controlled to satisfy our demands by changing these parameters. Also it is found that the diffracted pulses have a displacement along the time-axis compared with readout pulse. Results of our study can be used in pulse shaping and designing new optical devices based on multiple layers of volume holographic grating.

In this paper, we experimentally demonstrate a wavelength division multiplexing (WDM) transmission system supporting converged transport of multi-wavelength ultrawideband (UWB) signals. Optical signals of 8×10 Gb/s are successfully transmitted through a 25 km single mode fiber (SMF). This paper mainly studies the influence and change of the waveforms and spectra of the optical signals during the co-propagation process.

We analyze and optimize the parameters of the Type I spontaneous parametric down-conversion (SPDC) process in BiB₃O₆ (BIBO) crystal directly from calculations. This can be used to construct a system to generate ultrafast entangled photon pairs, which play an important role in quantum communication, quantum positioning, and quantum clock synchronization. Our work on the problem makes it clear that the optimal phase matching orientation in the process of SPDC is a key mechanism in the BIBO crystal in a way that appears not to have been appreciated before. In the case of ω = 0.405 μm , the numerical results of the optimization parameters at room temperature ( 295 K ) are:θ = 152.00° ,φ = 90° , and d _eff = 3.48 pm/V . Finally, we use a pair of 0.6 mm thick biaxial BIBO crystals to construct an ultrafast entangled photon source, where the crystals are stacked together perpendicularly and pumped by a 405 nm pulsed laser doubling from a Tsunami mode-locked Ti:sapphire laser.

We construct a compact polarization-entangled photon source using type-II degenerate spontaneous parametric down-conversion (SPDC) in beta-barium borate (BBO) crystal pumped by a 405 nm violet laser diode. In order to compensate the spatial displacement and the temporal delay due to the birefringence and dispersion effect of signal and idler photons, we make the down-converted photon pairs pass through a half wave plate and an additional BBO crystal with the half thickness of the original one. This improves the visibility of two-photon interference by eliminating the distinguishability of the paired photons. We measure the polarization correlations by two adjustable polarization analyzers in two conjugate bases, H/V and +45°/-45°, respectively. The polarization analyzer consists of a polarization beam splitter cube preceded by a rotatable half wave plate. When rotating one of the half wave plates and keeping the other one at fixed angle, we obtain the expected sin2 dependence of the coincidence counts. The highly visible sinusoidal coincidence indicates the violation of the Bell inequality and demonstrates the high quality of the polarization-entangled photon source. This compact polarization-entangled photon source is easily configurable and robust to demonstrate optical quantum information processing.

III-V compound semiconductor visible-spectrum light-emitting diodes (LEDs) have received much attention for their important applications in several areas. The AlGaInP semiconductor materials are capable of emitting light of red and orange, and the InGaN semiconductor materials are capable of emitting light of green and blue. Those four colors of LED chips are encapsulated with epoxy in same conditions. In this paper, the junction temperature of power AlGaInP and InGaN LEDs were measured at different drive current by forward - voltage method .Optical and electrical parameters under different temperature were also measured. Thermal properties of power AlGaInP and InGaN LEDs were analyzed for strong dependence of optical and electrical characteristics of power light-emitting diodes on the diode junction temperature.

A coupled waveguide with fluctuating coupling coefficients could influence its light transmission characteristics. According to Fourier theorem, an arbitrary fluctuation function can be expanded as a superposition of harmonic functions of position of different spatial frequencies. This paper investigates how the amplitude and the spatial frequency of the harmonic functions of the fluctuation influence the light transmission, including CW, quasi-CW and pulse cases. The fluctuation of the coupling coefficient is assumed as a sine waveform. The numerical results show that the influence of the fluctuation of the coupling coefficient on the coupling behaviors is negligible even the fluctuation amplitude of the coupling coefficient is as high as 30% if the period of the fluctuation is less than 2π/3. When the period of the fluctuation is larger than 2π/3, the switching performance degrades.

All optical Schmitt trigger based on Kerr bistability in quasi periodic Thue-Morse photonic crystals is investigated. Finite difference time domain is used to investigate the Schmitt trigger operation in one dimensional nonlinear Thue-Morse Photonic crystals.

Recent work has shown that weak applied magnetic fields of several tens of mT can lead to a change of several percent in the (photo)conductivity of organic semiconductor devices. However, it remains to be determined whether the applied magnetic field modifies the (photo)carrier density, their mobility or both. We use magneticfield- dependent time-of-flight spectroscopy to disentangle these two possibilities. We find evidence that the magnetic field leads to a decrease in the photocarrier time-of-flight. We also examine organic magnetoresistive devices in the frequency domain to complete the characterization of the time-dependent field-effect response.

The photocurrent responses were investigated for the biomolecular bulk-hetero junction of chlorophyll α (Chl-α) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-1-phenyl-(6,6)C₆₁ (PCBM) in the temperature range between 300 K and 1.5 K under the magnetic field up to 8 T. The chopped-light photocurrent decreases on lowering the temperature. Below 10 K, photocurrent decrease was observed under the applied magnetic field. Decay of the photocurrent observed at 10 K was ascribed to the formation of the charged trap under light irradiation. The magnetic field effect (MFE) observed in this device was found to be very similar to that observed in P3HT:PCBM bulk-hetero junction at low temperatures.

We develop a systematic approach of quantifying spin-orbit coupling (SOC) and a rigorous theory of carrier spin relaxation caused by the SOC in disordered organic solids. The SOC mixes up- and down-spin in the polaron states and can be characterized by an admixture parameter. The spin relaxation rate is found to be proportional to the carrierhopping rate, or equivalently, carrier mobility. The spin diffusion length depends on the spin mixing and hopping distance but is insensitive to the carrier mobility. The SOCs in tris-(8-hydroxyquinoline) aluminum (Alq₃) and in copper phthalocyanine (CuPc) are particularly strong, due to the orthogonal arrangement of the three ligands in the former and Cu 3d orbitals in the latter.The theory quantitatively explains the recent measured spin diffusion lengths in Alq₃ from muon spin rotation and in CuPc from spin-polarized two-photon photoemission.

Electrically Detected Magnetic Resonance (EDMR) was used to investigate the influence of dye doping molecules on spin-dependent exciton formation in Aluminum (III) 8-hydroxyquinoline (Alq₃) based OLEDs with different device structures and temperature ranges. 4-(dicyanomethylene)-2-methyl-6-{2-[(4-diphenylamino-phenyl]ethyl}-4H-pyran (DCM-TPA) and 5,6,11,12-tetraphenylnaphthacene (Rubrene) were used as dopants. A strong temperature dependence have been observed for doped OLEDs, with a decrease of two orders of magnitude in EDMR signal for temperatures above ~200 K. The signal temperature dependence were fitted supposing different spin-lattice relaxation processes. The results suggest that thermally activated vibrations of dopants molecules induce spin pair dissociation, reducing the signal.

We investigate the light concentration effect of localized surface plasmon resonance by embedding a layer of silver nanoparticles in the low band gap polymer bulk heterojunction solar cells. Particle electromagnetic interaction is demonstrated by using the 3-dimensional finite-difference time-domain computational method. This nanostructure exhibits broadband optical absorption enhancement and weak dependence on incident light polarization. The optical concentration mechanism is discussed by near-field distribution analysis. This method can be used to optimize the design of plasmonic organic solar cells for high energy conversion efficiency.

TiO₂ film was deposited on quartz substrate by sol-gel method. X-ray diffraction analysis and Raman scattering measurement indicate that the TiO₂ film is the pure rutile phase structure. From photoluminescence spectra, it is found that the TiO₂ film shows a near-infrared luminescence band centered at about 832 nm, and two visible luminescence bands centered at about 426 nm and 524 nm, respectively. The refractive index n, extinct coefficient k, optical band gap EOBG and thickness d of TiO₂ film were extracted by fitting transmission spectra with the Adachi's dielectric function model and a three-phase layered model. It is found that n value increases and then decreases with increasing wavelength, while k decreases continuously. The thickness of TiO₂ film is about 297 nm. EOBG value is about 3.72eV and larger than that attained by Tauc's law, which is about 3.28eV.

The Bi_1-xLa_xFe_1-yMg_yO₃ thin films were fabricated on Si (100) by sol-gel method. X-ray diffraction analysis shows that all the films are perovskite structure with space group R_3C with x and y range from 0 to 0.1 altogether. Moreover, the co-doped La and Mg distorted BiFeO₃ lattice structure which induced from Raman study. The refractive index n and extinction coefficient k of the co-doped BiFeO₃ film obviously get larger with the La and Mg concentration, and the band-gap energy of BiFeO₃ was found to be 2.45±0.02ev and that of Bi _0.95 La _0.05 Fe _0.95 Mg _0.05 O₃ and Bi _0.9 La _0.1 Fe _0.9 Mg _0.1 O₃ were 2.40±0.02ev and 2.35±0.02ev, respectively. Our results suggest that small amount of La and Mg doping can change optical property of BiFeO₃ material.

The LuFeO₃ (LFO) nanocrystalline films with the average grain size of 20 nm have been grown on silicon (100) substrates by pulsed laser deposition. X-ray diffraction (XRD) analysis shows that LFO films are polycrystalline. The microstructure and surface morphology of LFO film are analyzed by Atomic force microscope (AFM) and the surface shows the film is compact. Spectroscopic ellipsometry (SE) was used to extract the optical properties of LFO films in the 1.1-3.1 eV (400-1100 nm) photon energy range at room temperature. By fitting the measured ellipsometric parameter data with a multilayer model system for the LFO thin films, the optical constants and thicknesses of the thin films have been obtained. The refractive index n and extinction coefficient k of the LFO thin films both decreases with increasing thickness.

Here we report a simple and cost effective fabrication technique, which created large area vertical Si nanowires (diameter in ~200 nm) by means of silver induced wet chemical etching on single crystalline Si substrates. By this technique, Si nanowires were fabricated on single crystalline in aqueous 5M HF and 0.02M AgNO₃ solution at room temperature. The scanning electron microscope (SEM) images indicate that etched silicon wafers consist of dense and nearly vertically aligned one-dimensional nanostructures. Length of Si nanowires was found to increase linearly with etching time (0-300 min). The mechanism of vertical nanowires formation can be understood as being a self-assembled Ag induced selective etching process based on the localized microscopic electrochemical cell model. A low reflectivity averaged ~1.7% from 450 to 790 nm was observed. The nanometer scale rough surface can make water droplet either in the so-called Wenzel or the Cassie regime, which can increase contact angle (CA). High CA makes the surface hydrophobicity and self-cleaning. Water CA (150°) was observed on the etched Si surface. Such antireflection (AR) and self-cleaning surface may have potential applications for silicon solar cells.

AlN epilayers were grown directly on sapphire (0001) substrates using a combined growth scheme, a low temperature nucleation layer and a high temperature pulsed-atomic-layer-epitaxy layer obtained via metal organic chemical vapor deposition. The effects of growth temperature on properties of AlN films were investigated by atomic force microscopy, high resolution X-Ray diffraction and transmittance spectral. Due to the strong influence of growth temperature on the mobility of Al adatoms and parasitic reaction, a different surface morphology and growth rate for AlN films were obtained by varying the growth temperature.

GaN epilayers were grown on the AlN buffer layer obtained by pulsed atomic-layer epitaxy (PALE). The influence of PALE-AlN buffer thickness on the quality of GaN epilayers were investigated by atomic force microscopy, high resolution X-Ray diffraction, and photoluminescence (PL) spectrum. The strain states of the GaN epilayers were studied by Raman spectrum. It was found that the thickness of PALE-AlN buffer layer is a key parameter that affects the quality of GaN epilayer, and a proper growth period of PALE-AlN buffer layer leads to excellent surface morphology, crystal quality and optical properties of the GaN epilayer.