This PDF file contains the front matter associated with SPIE-OSA-IEEE Asia Communications and Photonics Vol. 7631, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

We present fabrication and characterization of 1.3-μm InAs quantum dot (QD) vertical cavity surface emitting lasers (VCSELs) and QD-VCSEL arrays. The continuous-wave (CW) output power of single QD-VCSEL of 1.2 mW with lasing wavelength of 1.28 μm is obtained at room temperature (RT) at a bias current of 15 mA without power saturation. The low threshold current of 1.1 mA can be achieved for the single mode device. We investigate the 3-dB modulation bandwidth of QD-VCSELs with oxide aperture size of 5-μm, 10-μm and 15-μm in the small signal frequency response measurements. Modulation bandwidth of 2.65 GHz is achieved for single-mode QD-VCSEL with oxide aperture size of 5 μm at a bias current of 4.5 mA. The maximum modulation bandwidth of 2.5 GHz can be obtained for multimode QD-VCSEL with oxide aperture size of 10 μm at a bias current of 7 mA. The 61 QD-VCSELs array is also investigated at RT without optimization. Maximum CW output power of 28 mW and pulsed output power of 18 mW are demonstrated for 2-D QD-VCSEL array with threshold current of 50 mA. The far field pattern beam angle of QD-VCSEL arrays at two perpendicular directions are about 18 degree.

A bidirectional grating serving both, as a polarization beam splitter and a vertical coupler for Silicon on Insulator nanophotonic circuits is fabricated and characterized. The measured coupling efficiency is as high as 43%. The demonstrated device has a large 3-dB bandwidth and a high extinction ratio between two orthogonal polarizations.

To our knowledge, this is the first report of a monolithically integrated distributed feedback (DFB) semiconductor laser array based on reconstruction-equivalent-chirp (REC) technology. A laser bar with 30 different lasers is obtained, lasing at 30 different wavelengths under single longitudinal mode. The typical threshold is about 40mA to 60mA. The typical slope efficiency is about 0.07 mW/mA to .13 mW/mA. Tested under the injection current of 100mA, the side mode suppression ratios (SMSR) range from 24.9dB to 46.8 dB, with an average of 37.2dB. The proposed method is presented in hoping to make a positive contribution to large-scale photonics integrated circuits (PIC) research for the nextgeneration fiber-optic networks.

We propose a prototype of a silicon-chip-based frequency quadrupling system integrating a single-drive silicon Mach- Zehnder modulator and a race-track resonator as an optical differentiator. A proof-of-concept demonstration of 40-GHz millimeter-wave signal generation using 10-GHz driving signal is experimentally provided. The factors that impacting the purity of the RF spectrum are discussed through simulation.

As one of the most rapidly growing areas of the tunable semiconductor diodes, tunable vertical cavity surface-emitting lasers (VCSELs) have been focused on and the wavelength tuning characteristics have been investigated in detail. By applying an electrostatic bias between the semiconductor and the cantilever which is an external reflector apart from the device, the stimulated wavelength can be continuously modulated with a continuous tuning over a 10nm spectral range. It is found that, as the tunable VCSEL operate in its stable regime, the displacement of the cantilever will result in a periodic variation in the intensity and wavelength with a period of half the resonant wavelength. We also found the same phenomenon in the tunable RCLED. In addition, based on our observations, precise analysis is presented from the Lang and Kobayashi model. Our results show an adequate match between theory and experiments for the detailed tunable spectra. These results can be used to greatly enhance the performance of tunable VCSEL and RCLED.

The relationship between the wavelength shift and the thickness of the air gap was investigated by the Optical Standing Wave Method; the modal characteristics of the MEMS tunable Vertical Cavity Surface Emitting Lasers were also analysed in the Dielectric Cylindrical Waveguide by the Improved Effective Index Model.

A long wavelength multichannel tunable photodetector array was fabricated based on multistep Fabry-Pérot filter by using the heteroepitaxy growth of InP-In_0.53Ga_0.47As-InP PIN structure on a GaAs based GaAs/AlAs Fabry-Pérot filter structure. High quality heteroepitaxy was realized by employing a thin low temperature buffer layer. The array can detect multiple channels, and the tuning range of each detector is about 10nm. A spectral linewidth of 0.5nm, a quantum efficiency over 25%, and a 3dB bandwidth of 9.2GHz were simultaneously obtained.

An optical switch is fabricated based on nanocrystalline vanadium oxide (VO_x) thin film using micromachining technology. An "on" state with semiconducting phase to an "off" state with metallic phase is controlled by applying a DC power to Aurum electrodes of the optical switch. The optical switching performance for the fabricated device is investigated at optical communication wavelength of 1.55μm. The heater power requires to achieve switching action is about 15mW. The testing results show that the extinction ratio and switching response time are 14dB and 2ms, respectively.

In this paper, we demonstrate that a prism coupling characterization technique can lead to simpler Waveguide Bragg Grating (WBG) designs and easier fabrication process by avoiding channel transmission. The experimental results have shown that the incident laser beam's collimation was maintained after coupling to a planar waveguide. A characterization set-up using two prisms was designed for measuring transmission characteristics of integrated structures and eventually planar waveguides in the visible or in the IR range. Since a reasonable overall optical efficiency of 10% has been demonstrated for this set-up, the prism approach can be eventually utilized in Bragg Grating structures characterization.

The thermal nonlinear optical effect is observed in a microring resonator (MRR) based on a small SU-8 polymer ridge optical waveguide. It is found that the resonant wavelength blue shifts almost linearly with a slope of about -0.8 pm/mW as the input power increases (which causes the increase in temperature and consequently the decrease of the refractive index). Both the strong light-confinement of the air-clad waveguide and the strong light-enhancement of the MRR cavity contribute to the significant nonlinearity. The absorption mechanism is analyzed in detail, and the absorbance of about 0.179 cm^-1 (around 1560 nm) is obtained.

A bending directional coupler is presented to enhance the evanescent coupling between a compact deeply-etched III-V/Si hybrid microring laser and its small Si bus waveguide. With the present design, one could realize a sufficient evanescent coupling between the III-V/Si hybrid microring even when the gap between the microring and the bus waveguide is relatively large gap (~ 400nm). This makes the fabrication easier.

We propose logic XOR gate and format conversion for carrier-suppressed return-to-zero differential phase-shift keying (CSRZ-DPSK) signals using non-degenerate four-wave mixing (FWM) in a highly nonlinear fiber (HNLF). Due to the linear relationship of the complex amplitudes between output and input optical waves, the three generated idler waves by three non-degenerate FWM processes take the return-to-zero differential phase-shift keying (RZ-DPSK) format and the logic XOR result of three input CSRZ-DPSK signals. All-optical 40 Gbit/s multicasting CSRZ-DPSK logic XOR operation and CSRZ-DPSK to RZ-DPSK format conversion are simultaneously demonstrated in the experiment.

All-optical clock recovery is a key technology in all-optical 3R signal regeneration (Re-amplification, Retiming, and Reshaping) process. In this paper, a monolithic integrated three-section amplified feedback semiconductor laser (AFL) is demonstrated as an all optical clock regenerator. We fabricated a three-section AFL using quantum well intermixing process without regrowth instead of butt-joint process. The tunable characteristics of three-section AFL were investigated, and all optical clock recovery for 40Gb/s return to zero (RZ) 2³¹-1 pseudorandom binary sequence (PRBS) is demonstrated experimentally using AFL with time jitter about 689.2fs.

We experimentally demonstrate all-optical clock recovery (CR) from the nonreturn-to-zero (NRZ) data without any preprocess measure. Multi-quantum-well (MQW) Fabry-Pérot semiconductor optical amplifier (FP-SOA) plays the dual role of the data format converter and the clock recovery device. To achieve amplitude equalization of the recovered clock pulses, a self-nonlinear polarization switching (SNPS) including the FP-SOA itself, two polarization controllers (PCs) and a polarization beam splitter (PBS) is employed. Using the presented scheme, stable and low jitter 35.80 GHz optical clock pulses were directly extracted out from input NRZ data. This scheme has some distinct advantages such as being transparent to data format, free preprocess, free pre-amplification, convenient tuning, good tolerance to long "0s" data, and good tolerance to wavelength drifting of input data.

A novel scheme for 40Gb/s all-optical nonreturn-to-zero (NRZ) to polarization-shift-keying (PolSK) format conversion, based on transient cross-phase modulation (T-XPM), is proposed and experimentally demonstrated using a single semiconductor optical amplifier (SOA) assisted by optical bandpass filter (BPF). This proposed NRZ-PolSK format conversion is robust in terms of simple structure and high bit rate operation. In addition, it can be realized without wavelength change.

In this paper, we review special high bandwidth multimode fiber and their role in upgrade path of optical interconnection to 40Gbps and 100Gbps in green data centers and high performance computing.

A new photodetector was designed with Metal Aperture Arrays filter in this paper. The shape and dimensions of the holes in an array do influence its transmission spectrum compare to the conventional photodetector. Hole array and annular aperture arrays were discussed.

We present the benefits and limitations for designing complex optical semiconductor-based integrated structures by means of advanced numerical modeling. Multi-section tunable laser designs are presented and their tuning properties are analyzed for different architectures. We introduce a model of an integrated SOA with electroabsorption modulator. Its spectral properties are analyzed function of the parameters of the absorber section, showing the influence on the extinction ration of the generated signal. An InP-type Mach-Zehnder modulator is designed, illustrating the models of Kerr, Frank-Keldysh and QCSE effects. An example of a photo-detector demonstrates how dimensions and absorption parameters can be optimized to increase its detection bandwidth.

In this paper, a novel structure for detection of two different wavelengths in mid-infrared region is proposed. By attaching a capturing well to the active region, a common transportation path for electron excited by two different wavelengths is introduced. Calculated values for responsivity and detectivity in the designed Quantum Cascade Photodetector structure at 120K are: R₁ (λ=6.85μ m) =67.5 mA/W, R₂ (λ=12.35μ m) =118.5mA/W and D₁ (λ=6.85) =6.89×10⁷J, D₂ (λ=12.35) =1.2×10⁸J, respectively.

Compact, efficient, narrow linewidth, fiber based THz sources have been achieved by using the monolithic high power single-frequency pulsed fiber lasers in MOPA based on difference-frequency generation (DFG) in nonlinear optical crystals. We have observed the external cavity enhancement of DFG THz generation by using ZnGeP2 for the first time, and implemented a high spectral resolution THz spectrometer based on the developed fiber-based tunable narrow linewidth THz source.

We demonstrate a novel THz quantum cascade laser (QCL), emitting at two widely separated wavelengths 33 μm, 51 μm, simultaneously, based on GaN/AlGaN quantum wells. The large LO-phonon energy (~ 90 meV) and ultrafast resonant phonon depopulation of lower radiative levels lead to an excellently enhancement in operating temperature.

By using terahertz time domain spectroscopy (THz-TDS) system, the terahertz dielectric properties of various gallium arsenides were tested in the frequency range extending from 0.2 to 1.5 THz. The power absorption coefficient and refractive index of various resistivity gallium arsenides were measured and compared. The refractive index of the high resistivity and ultra-high resistivity GaAs are equal to be 6.53 and 5.9, respectively. The variation of the refractive index of the GaAs was less than 1%, ranging from 0.2 to 1.5THz, but the absorption coefficient of the ultra-high resistivity GaAs showed very different frequency-dependent behaviors, ranging from 0.02cm-1 to 2.21cm-1, within the investigated frequency range. The results show that the ultra-high resistivity GaAs will be a good candidate material for terahertz transmission waveguide.

We introduce a compact, low-power electro-optical switch on a silicon-on-insulator circuit through heterogeneous integration. A 10μm diameter III-V microdisk cavity is employed as the switching element. Switching of a 10Gbps optical signal is demonstrated by sweeping the bias between -1.1V and +0.9V with 15dB extinction ratio and 1.2ns switching speed.

A compact electrically-pumped hybrid silicon microring laser is realized on a hybrid silicon platform. A simplified, selfaligned, deep-etch process is developed to result in low-loss resonator with a high quality factor Q>15,000. Small footprint (resonator diameter=50 μm), electrical and optical losses all contribute to lasing threshold as low as 5.4 mA and up to 65 °C operation temperature in continuous-wave (cw) mode. Outcoupling- and bus waveguide width-dependent studies are conducted for optimizing device structure. A simple qualitative study in current-voltage (IV) characteristic shows that dry etching through active region leads to <3× more leakage current at the same reverse bias than wet etch counterpart. It indicates a relatively good interface with tolerable surface recombination from deep dry etch. The spectrum is single mode with large extinction ratio (>40 dB) and small linewidth (<0.04 nm) observed. The unique bistability operation in ring resonator structure is also demonstrated.

The photoluminescence spectra of amorphous silicon rich silicon nitride films with various compositions were investigated. Two main luminescence peaks were identified for all samples and blueshift of photoluminescence were observed after annealing treatment. With the help of X-ray photoelectron spectroscopy and Fourier transform infrared measurement, the chemical composition and bonding environment of samples, which were grown with different reactant gases flow rates of plasma enhanced chemical vapor deposition, were analyzed. According to all these measurement results, it is confirmed that the main luminescence centers are radiative recombination defects, such as silicon and nitride dangling bonds. With proper deposition conditions, all these radiative recombination defects could be activated at the same time, so that ultra-wide photoluminescence spectra with full width at half maximum of about 250nm ~ 300nm were obtained in visible region.

In this study, the indium tin oxide (ITO) was etched by an inductively coupled plasma (ICP) etcher using Cl₂/C₂H₄/Ar as the etching gases. The etch rates were studied as a function of RF power, inductively coupled plasma (ICP) source power, working pressure and gas mixing ratio. We found that the RF Power plays a dominant role in the elevation of the etch rates, which indicates that the ITO etching in this study is a physical mechanism dominated etching. The state of the photoresist (PR) was observed after each experiment. As expected, the high power, which generally leads to a high etch rate, would distort the PR mask, resulting in a bad etched profile of the sample. Through research, we got a relatively high etch rate (~ 200nm/min) with the shape of PR mask remain undistorted. The profile, which includes the morphology of the film sidewall and surface after the etching process, was sensitive to the gas mixing ratio. We adjusted the gas mixing ratio, and observed the profile using a scanning electron microscope (SEM), then optimal morphology was get as the Cl₂/C₂H₄/Ar at the value of 30sccm/7sccm/50sccm.

Molecular dynamics simulations using the Tersoff potential have been performed to investigate the perturbation effects caused by different kinds of the point defects (vacancies and substitutional impurities) on the strained and relaxed Si matrices. Lattice distortion, mean square displacement, pair correlation function and vibrational spectra are studied. It is found that Ge substitution lead to little distortion of the Si matrix. However, vacancy and C substitution lead to more distortion. Diffusion directions of Si atoms around different kinds of point defects are different. When C substitution is introduced in the relaxed Si matrices or Ge substitution is introduced in the strained Si matrices, the system needs longer time to reach equilibrium. The crystallinity and symmetry degree of relaxed Si matrices are more satisfying than those of strained Si matrices after relaxation. Changes of the vibrational spectra caused by vacancy and C substitution are obvious. All above have a great effect on the photoelectric properties of the materials.

In this work, we mainly focused on the luminescence properties of ZnS:Mn nanocrystals. Various samples of ZnS:Mn have been characterized at different doping concentration, annealing temperature, spin speed and time. The present study shows the application of spin speed, spin time, doping concentration and temperature affect the luminescent intensity performance. Luminescent intensity becomes higher with the increasing film thickness. Spin speed and spin time are two major concerns for coating film to a demanded thickness on the glass slide. Film thickness is the main reasons of the increasing intensity with spin speed and time. Temperature dependent PL measurements provide thermally activated energy transfer from other defects to Mn²⁺ ions. As the temperature increase, the carriers can be trapped at Mn sites, enhancing the luminescence spectra. Meanwhile, the quenching process influenced the PL intensity with doping concentration. This process occurs at high Mn concentration which the energy transfer from Mn ions to the other nearest Mn atom is weak. Therefore, the luminescence of transition from ⁴T₁ to ⁶A₁ of ions becomes stronger. From this reason, it is shown that luminescent intensity increased with higher doping concentration but decreased with higher annealing temperature, spin speed and spin time during spin coating process.

A dmit^2- salt: [(C₄H₉)₄N]Au(dmit)₂ was synthesized. Its third-order nonlinear optical properties of its acetone solution were investigated by Z-scan technique using a pulsed laser with 28 ps duration and 10 Hz repetition at 532 nm. The third-order nonlinear refractive index n₂ and nonlinear absorption coefficient β of the sample solution were obtained to be about 4.997×10^-12 esu and 1.818 cm/GW at the concentration of 2×10-3 M. The second-order hyperpolarizability for its molecular was estimated to be as large as 2.74×10^-31 esu, suggesting [(C₄H₉)₄N]Au(dmit)₂ is a promising material for all-optical switching.

An organic material, 4,5-bis(benzoylthio)-1,3-dithiole-2-thione (BBDT), was synthesized. The thin film of BBDT doped into poly(methyl methacrylate) (PMMA) was prepared using spin-coating method. Its linear optical properties were characterized with prism coupler (SPA-4000, Korea). The third-order nonlinear optical (NLO) properties were investigated using Z-scan technique with pulses of picoseconds at 532 nm. The Z-scan spectra reveal a strong nonlinear absorption (reverse saturable absorption) and a positive nonlinear refraction. The nonlinear absorption coefficient is calculated to be 1.302×10^-9m/W. The nonlinear refractive index is 2.243×10^-9esu. The results show that the film exhibits a great nonlinear optical response.

Focusing Q-switched laser pulses into FC-72 medium, the transverse profiles and spatial evolution of beam in stimulated Brillouin scattering (SBS) are investigated experimentally by CCD camera and digital image processing technology, and the rules of spot size versus pump energy are obtained. The results show that the transverse profiles of backward SBS spots with different pump energies are Gaussian or quasi-Gaussian profiles when pump beam is Gaussian. And the spatial profiles of SBS spots change from quasi-Gaussian to Gaussian when the incident energy increases from the threshold to several times the threshold. At the same time, the size of SBS spot decreases with the increasing pump energy on the whole.

A measurement of carrier recovery time in semiconductor optical amplifiers (SOAs) based on dual pumps four-wave mixing (FWM) is presented. The results show the carrier time is 91 ps, 79 ps and 63 ps at 120 mA, 180 mA and 240 mA, respectively, which agree to our expectation. The experimental results show the conversion efficiency keeps constant when the spacing of the two pumps varies within a small range.

In this paper we analytically study and evaluate the performance of a Spectral-Phase-Encoded Optical CDMA system for different parameters such as the user's code length and the number of users in the network. In this system an advanced receiver structure in which the Second Harmonic Generation effect imposed in a thick crystal is employed as the nonlinear pre-processor prior to the conventional low speed photodetector. We consider ASE noise of the optical amplifiers, effective in low power conditions, besides the multiple access interference (MAI) noise which is the dominant source of noise in any OCDMA communications system. We use the results of the previous work which we analyzed the statistical behavior of the thick crystals in an optically amplified digital lightwave communication system to evaluate the performance of the SPE-OCDMA system with thick crystals receiver structure. The error probability is evaluated using Saddle-Point approximation and the approximation is verified by Monte-Carlo simulation.

The upconversion fluorescence spectra of Er³⁺/Yb³⁺: PLZT excited at 980 nm were measured from 10K to 320K. A model for the dynamics of frequency upconversion process was proposed. Based on this model, the upconversion luminescence intensities were fitted as a function of temperature and the temperature characteristics of upconversion luminescence were discussed.

Temporal imaging is one of the important research issues using time-lens. The theory of temporal imaging using time lens is discussed briefly. The experiment to perform optical pulses compression is demonstrated and the problem is further discussed by numerical simulation in this article.

We theoretically propose soliton-like compression of femtosecond pulses in two-segmented quasi-phase-matching (QPM) grating. By using group-velocity (GV) matching scheme with type-I (o+o:e) second harmonic generation (SHG), we numerically show soliton-like compression of femtosecond pulses with higher quality factor, lower intensity threshold and better spatial-temporal pattern in segmented QPM than periodic structure with the same total crystal length.

The recently demonstrated high-power (50W from a 20μm stripe) picosecond (30ps) lasing from a laser diode has led us to address the internal Q-switching phenomenon, discovered four decades ago and not yet fully understood. We found that the realization of a nanosecond or picosecond mode in a diode depends on the doping profile across the structure.

We have developed a terawatts high intensity, sub-hundred femtosecond ultra-short pulses, 248.6 nm ultraviolet laser systems, with dye seed laser in blue-green regime, amplified in the multi-stage dye amplifiers and then frequency doubled and finally amplified with multiple-passes KrF amplifier. We have characterized the system performances, the amplified interaction volume, the amplified spontaneous emission optimization, the Excimer amplifier and the system merits.

With the wide scale deployment of 40Gbps in carrier networks underway and 100Gbps products on the horizon, 40Gbps and 100Gbps modules based on Multi Source Agreements (MSA) are gaining considerable interest and market acceptance. This paper discusses developments in 40Gbps and 100Gbps line side DWDM MSA modules and CFP based client side MSA modules as suppliers strive to address various system and network applications.

Advanced InP technology is the enabling technology to achieve monolithic integrated 300-pin MSA compatible 43 Gb/s (RZ-)DQPSK transponder module with high performance. The integrated platform offers footprint, power, and cost reduction for next generation products.

We present a hybrid integrated 40 Gb/s DPSK receiver module with athermal free-space delay-line-interferometer (DLI) as well as the opto-electric dc-characterisation algorithm based on the Müller-Matrix analysis. It offers wideband operation of 100 nm in the C+L band, a FSR of 43 GHz, PDFS of 350 MHz, TDFS (0-75°C) of 0.8 GHz and a saturated differential output voltage-swing of 600 mVpp. 43 Gb/s NRZ-DPSK back-to-back system experiments demonstrated an error-free transmission and an OSNR sensitivity of 18 dB (BER=10^-9, PRBS2³¹-1).

In this paper, methods of tunable Mach-Zehnder (MZ) modulator set-up in a Tunable Transmitter Assembly (TTA) have been investigated. Firstly the basic theory of the MZ modulator is introduced, and then there is discussion of MZ characterization in a Tunable Compact MZ modulator module (TCMZ). Secondly, dynamic control methods for accurately setting up the operating point for the MZ modulator during TTA AC test have been presented. Finally, detailed experiment results of a transmitter module with the method implemented have been analyzed. It demonstrates the methods improve application performance of the TTA.

In this paper we report a 850nm oxide VCSEL operating at 20 Gbit/s (PRBS31) with a 5 dB Extinction Ratio, based on a volume manufacturing platform with MOCVD grown GaAs/AlGaAs epi-material. We present detailed time and frequency domain VCSEL characterization results, and a finite element simulation showing good agreement with experimental data.

The formation of the ground states in a GaAs/AlGaAs asymmetric coupled quantum-well is analyzed with the use of coupled-mode theory. Based on perfect work condition of traveling-wave modulators, the GaAs/AlGaAs coupled quantum-well is optimized and the optimal coupled quantum well has a large electro-refractive index change at low absorption loss.

A novel quantum dots(QDs) optical fiber amplifier was proposed and demonstrated. It was fabricated by dip-coating the PbSe quantum dots doped sol onto the taper region of fiber coupler. The PbSe quantum dots was synthesized according to a colloidal method. And a lower refractive index sol was also synthesized as the host of PbSe QDs. A standard single mode fiber was used to make the fusion tapered fiber coupler which had double input and output ports. With the simple structure, a signal and a pump can be injected into the amplifier and excite the PbSe QDs through evanescent wave. As shown in the experimental results, the amplified light wave was observed at 1550nm wavelength with 980nm wavelength LD as pump.

We study the characteristics of nano-optical antenna made of two gold nano-particles by three dimensional numerical calculations at visible and near infrared band. To carry the computational burden and guarantee the precision and speed of a 3D FDTD calculation, adaptive mesh refinement technology is used. We first highlight the concrete way of controlling over the emitter position to fulfill the requirements of larger spontaneous emission enhancement. By exciting the resonance of surface plasmon polaritons (SPPs), we find that the far field directivity is strongly influenced and obtain around 5000-fold spontaneous emission enhancement. Choosing the incident wavelength of 600nm, we compute the decay rates and radiant efficiency as a function of antenna geometry limitations, showing the particle with an aspect ratio of L/R=4 is best for enhancing spontaneous emission. Furthermore, we proceed a spectrum analysis and find an exact relationship between the particle length and resonant wavelength.

A series of Yb-doped silica-based nanoparticles were fabricated in the MCVD process. Their compositions and doping levels were well controlled from 0 to 0.53 wt% for Yb and from 0 to 2.1 wt% for Al. The nanoparticles are of about 21.3 ± 4.6 nm in size, but their sizes and NIR absorption are influenced by the Al concentration. At a fixed Al doping level, the NIR absorption depends on the Yb concentration. The nanoparticles exhibit a strong composition dependence of the photodarkening induced by the X-ray irradiation.

We report on the synthesis of new magneto-optical materials with excellent optical and magneto-optical (MO) properties for visible-range and near-infrared applications. Bi-substituted composite garnet films fabricated with excess bismuth oxide content using RF co-sputtering and conventional oven-annealing processes are found to possess simultaneously a record-high MO quality and strong uniaxial magnetic anisotropy. The films demonstrate nearly-square hysteresis loops with specific Faraday rotations of up to 10.1 deg/μm at 532 nm and up to 2.6 deg/μm at 635 nm, which are significantly larger than these measured in garnet films of the same composition prepared without extra bismuth oxide content. Record-high MO figures of merit are demonstrated in our composite garnet materials due to a significant reduction in the optical absorption coefficients achieved across the visible spectral range, thus making garnet-oxide composites highly attractive for use in a range of magneto-optical applications.

With the rapid development of all-optical network, we bring forward more and more requirements to the performance of the optical switches. Therefore, a novel magneto-optic switch based on nanosecond pulse is designed and investigated in this study. It is characterized by no moving parts, high switching speed, and small size etc. The research of magnetooptic switch mainly involves the design of optical route and nanosecond pulse generator. The optical route designment includes the selection of magneto-optic crystal, the route designment and performance analysis of polarized light in the MO switches, as well as the design of magnetic route in Faraday rotator. A bismuth-substituted rare-earth iron garnet single crystal is chosen as magneto-optic material, and a current solenoid is used to generate the applied magnetic field. The design of nanosecond pulse generator is based on the avalanche multiplier effect of avalanche transistor. Many kinds of avalanche transistor are studied in the experiment. The experimental results indicate that the rise time of the output pulse is about 2-5ns, the pulse width is about 6-20ns, while the pulse amplitude is about 30-150V, thereby it is satisfying for the magneto-optic switch used in all-optic network. By controlling the magnetization of the magneto-optic material, the optical beam can be stably switched and the measured switching time is about 100-200ns.

We report on laser emission from high quality quantum dot micropillar cavities. In these structures cavity quantum electrodynamics (cQED) effects are exploited to realize high efficient, low threshold lasing. We demonstrate that cQED effects allow for the observation of low threshold laser emission from a low number of InGaAs quantum dots embedded in optically and electrically pumped high-Q micropillar laser structures. For instance, lasing with threshold currents as low as 4 μA (160 A/cm²) is observed for electrically pumped microlasers at cryogenic temperatures. Moreover, single quantum dot controlled lasing effects are achieved in optically pumped micropillar lasers with particular high quality factors.

A partly gain-coupled ridge varied two-section DFB self-pulsation laser for optical microwave generating has been fabricated. It produces microwave with a wide tuning range of more than 135GHz. A successful locked to the microwave frequencies of 30GHz, 40GHz, 50GHz, 60GHz are demonstrated and a timing jitter below 300fs is detected.

Three types of Si-based photodetectors (PD) operating at long wavelength were introduced: the strained SiGe/Si multi-quantum-wells PD and Ge/Si islands PD with resonant cavity enhanced (RCE) structure, Ge p-i-n PD on silicon and SOI, Ge/Si avalanche photodetectors (APDs) with separate absorption, charge and multiplication (SACM) structure. The strained SiGe/Si MQW RCE PD and Ge/Si islands RCE PD has a threefold enhanced responsivity compared with the conventional PD without a resonant cavity. The Ge p-i-n PD on SOI has a responsivity of 0.65 A/W at 1.31μm and 0.32 A/W at 1.55μm. The 3dB bandwidth is 13.3GHz at reverse bias of 3 V. The Ge/Si SACM APD operating at 1310 nm have a responsivity of 4.4A/W (with a gain of 8.8) biased at 90% of break voltage.

A new photodetector was designed with Metal Aperture Arrays filter in this paper. The shape and dimensions of the holes in an arrays do influence its transmission spectrum compare to the conventional photodetector. Hole array and annular aperture arrays were discussed.

Two-dimensional subwavelength gratings (2D-SWGs) that consist of net-grid structure are studied by rigorous coupledwave approach (RCWA) and finite-difference-time-domain (FDTD) method. 2D-SWGs can be designed as infrared reflectors whose reflectivity can reach 99.98% at 1.55μm while maintaining reflectivity higher than 99% across the 1.47- 1.59μm wavelength range. We design these SWGs as the bottom mirrors in resonant cavity enhanced photodetectors (RCE-PDs) for optical communication system. Because SWGs can achieve high reflectivity as well as wide bandwidth, RCE PD's quantum efficiency is increased to 95.7% at 1.55μm and the device has a significant size reduction compared with using DBR bottom mirror.

New type of photodetector with cascaded waveguide grating filters as bottom reflection mirror is proposed. Greatly improved spectral response is shown to follow by the integration of waveguide grating into classical thin-film homogeneous layers. Calculation results for single grating, cascaded-double grating and cascaded-triple grating structure are demonstrated. An increasing rectangular spectral response is obtained by cascade two or three grating filters. Compared with traditional photodetector with distributed Bragg reflectors (DBRs), this new type of photodetector with the same materials require significantly fewer layers while maintaining narrow flat-top response, high peak efficiency and low sideband reflectance.

Using wafer scale optics, wafer scale integration, and wafer level packaging of image sensor, we developed small form factor (3.3mmx3.3mmx2.5mm), low manufacturing cost, Pb-free solder reflow compatible digital camera modules which are suitable for many applications including mobile electronic devices, automotives, security, and medical applications.

We introduce our recent works on directly-modulated AlGaInAs quantum-well lasers with semi-insulating buriedheterostructure for ultra-high-speed transmission. The short-cavity 1.3-μm-wavelength DFB lasers showed low-penalty transmission up to 13 km under direct modulation at 25 Gbps, as well as clearly-opened eye patterns by 40-Gbps direct modulation. For further reduction of driving current in the high-speed directly-modulated lasers, we developed the distributed reflector lasers with the active-region having the length of 100 μm or less, sandwiched by the passive reflectors. The fabricated distributed reflector lasers exhibited very high slope value of relaxation oscillation frequency of 4.0 GHz/mA^1/2 and more. The distributed reflector lasers emitting in 1.3-μm wavelength region achieved 40-Gbps direct modulation with the driving current of 2/3 of that by the DFB lasers. By the distributed reflector lasers of 1.55- μm-wavelength, high temperature 40-Gbps operation was realized as well as reduction of driving current.

Quantum dot-based diode comb lasers enable a single multi-channel-laser source for short-reach, high-speed WDM interconnects. In this paper, we demonstrate for the first time a 15 channel low RIN comb laser with 80 GHz channel spacing. We show that all the FP modes can be simultaneously directly modulated simply by modulating the pump current at 3.2 Gb/s, which indicates that the comb laser may be an ideal broadband light source in WDM-PON applications.We demonstrate that the whole comb laser spectrum can be amplified by a quantum dot SOA without increasing the relative intensity noise (RIN). Small signal amplification factor was measured as high as 30 dB and the saturated output power was as high as 15 dBm.

The miniature dual-inline (mini-DIL) pump laser becomes more attactive for compact optical amplifiers designs due to the advantage of smaller footprint, lower power consumption and lower cost. In this paper we report the development of a new generation of small form factor, high power "cooled" mini-DIL 980-nm pump lasers module for compact EDFA application.

A novel analytical band-gap analysis of one-dimensional or two-dimensional rectangular photonic crystals is presented. Compared with earlier analytical analysis, the transfer matrix method used in this paper has made the conclusions more directly. And the analytical expression of the band-gap can be generalized to complicated situations.

A special kind of one-dimensional magnetic photonic crystal (MPC) with the same refractive indices of the composites is investigated. We adopt the transmission matrix method to analyze the transmission properties of the special MPCs. The results indicate that the stop-band edges of TE mode coincide with those of TM mode, and the stop bands for both modes expand as the incident angle increases. Based on the incident angle domain method, the ODTR band determined by the wave impedance ratio can be enlarged using a heterostructure. Moreover, the requirement of ODTR of each sub-PC is unnecessary, which extends the range of materials.

Square microresonators with circular corners and a center air hole are simulated by the finite-difference time-domain (FDTD) technology and Padé approximation method. The results show that the deformed square resonators can increase mode Q factor at certain conditions. Furthermore, the hole in the square resonator can not only enhance the Q factor and the output coupling efficiency, but also have the ability to select the lasing mode.

In this paper, we derive an equivalent circuit model for quantum dot semiconductor optical amplifier (QDSOA) by employing rate equations for electronic transitions between QD's levels and also the optical power propagation. The different parts of equivalent circuits interact together to represent the gain recovery process, saturation properties and chirp behaviour in both linear and nonlinear operation regimes of QD-SOA. The equivalent circuits are then used for SPICE simulation. We have shown that SPICE simulation results agree well with the full numerically calculated results.

Electronic structures of InAs/GaAs cubic and truncated pyramidal quantum dots grown in (111) direction are showed in this paper. Continuum elastic theory is used to determine the strain distributions. Electronic energy levels are calculated by solving a three-dimensional effective mass Shrödinger equation including a strain modified confinement potential and piezoelectric effects. The influence of polarization effect to conduction band of quantum dot is discussed. It is found that polarization distribution is dependent on the shape of quantum dot.

Theoretical calculations of exciton in InAs/InP self-assembled quantum wires are presented in this paper. The Coulomb interaction between the electron and hole is calculated by using a fast Fourier transformation. In our simulations, strain effects are taken into consideration. Finally, we obtain the exciton binding energy in quantum wires by solving 1D Schrodinger equation along the quantum wire direction.

Colloid CdSe quantum dots have been synthesized and their photonic application as a two-wave mixing medium has been demonstrated. Large energy transfer from a strong pump beam to a weak signal beam has been observed and possible application in group velocity manipulation has been discussed.

Pump controllable nanosecond optical delay has been demonstrated using colloid CdSe quantum dots. The delay time can be easily manipulated by a pump beam. The physical mechanism for the two-wave mixing based group velocity manipulation has been investigated.

A new optical channel drop filter configuration was proposed based on two-dimensional (2D) square-lattice 45° photonic crystal ring resonators (PCRRs). The ring was formed by removing the line defect along ΓM direction instead of conventional ΓX direction. Its spectral information including transmission intensity, dropped efficiency and quality factor affected by different configurations like single-ring PCRR and cascaded dual-ring PCRR was numerically analyzed with 2D finite-difference time-domain technique. More than 830 spectral quality factor and 90% dropped efficiency can be achieved at 1550-nm channel for one single-ring PCRR. Two different light wavelengths can be dropped simultaneously for cascaded serial dual-ring PCRR. These findings make the 45° PCRR optical channel drop filters as an alternative to current micro-ring resonators for ultra-compact WDM components and high density photonic integration.

In this paper, we proposed the design of directional coupler integrated with ring resonator based on two-dimensional photonic crystals (2D PCs) to develop a triplexer filter. It can be widely used as the fiber access network element for multiplexer-demultiplexer wavelength selective in fiber-to-the-home (FTTH) communication systems. The directional coupler is chosen to separate the wavelengths of 1490nm and 1310nm. The ring resonator separates the wavelength of 1550nm. The transmission efficiency is larger than 90%. Besides, the total size of propose triplexer is only 19μm×12μm. We present simulation results using the finite-difference time-domain (FDTD) method for the proposed structure.

The work in this paper is based on a powerful function-fmincon in matlab and Finite Element Method, optimizing the shape and the position of dielectric rods surrounding the termination of a photonic crystal waveguide, in order to increase the directional emission. The method is simple, but can lead to useful results efficiently. More than fivefold improvement in power incident upon a target area over a simple termination is achieved, and the optimized structure is easier for fabrication.

As the applications of circular polarization (CP) antennas are widely used in the wireless communications, it is significant to improve the CP antenna performance in aspect of axial ratio at the boresite direction. A good CP performance is always desired. In this paper, we fabricate the amendatory one-dimensional photonic crystals for SHF reflector antenna based on previous simulation results to compensate the circular-polarization discrimination as encountered in many antenna's applications. The goal is to widen the beamwidth of radiation for crossed-dipole. The performance is evaluated by measuring the 3dB axial ratio. Transfer matrix theory of multi-layer theory is used to solve the field distribution cross layer. Although some tabulate plane-based (TPB) compensations can achieve a great improvement for the crossed-dipole based reflector antenna, but it can only compensate the CP in a specified direction and may distort in other directions. The one-dimensional approach can smooth the discrimination introduced by the reflector and noise. The energy distribution of TE/TM polarizations are regulated with a one dimensional photonic crystal to achieve a broader beamwidth, also the reflector antenna is fabricated and measured to validate the efficiency of the proposed approach. The measured results show that the beamwidth is much wider than that before compensation. The gain of 3D plot and the radiation patterns are also shown to verify if the side effect of compensation.

We investigate decoupling characteristics and efficiency of multiple coupled photonic crystal waveguides (M-CPCWs) using coupled mode theory on the basis of self-imaging principle. The three-, four- and eight-CPCWs are selected as the typical structures to discuss the general characteristics of the M-CPCWs. It is found that around the frequency where the multiple guided modes are almost degenerate, which leads to that the power transfer in the M-CPCWs is eliminated for any entrance. The frequency region for decoupling is insensitive to the number of coupled waveguides with the extinction ratios higher than -15dB. An optimization way by introducing a defect mode is utilized to enhance the decoupling efficiency. The simulation results are based on the finite-difference time-domain method. The decoupling of the M-CPCWs exhibit many advantages and may have practical applications in photonic integrated circuits.

A Low-loss Fabry-Perot interferometer (FPI) constructed in a two-dimensional photonic crystal (2D PhC) is proposed and investigated. The 2D PhC consists of a square-lattice of cylindrical silicon rods in air. It has flat equal frequency contours (EFCs) in the frequency range of 0.187-0.201c/a for TM modes. Two same line defects with spacing of d = 21√2 a, which is the physical length of the FP resonant cavity, are introduced in the PhC to form the FPI. The two line defects have high reflectivity and low transmission. Their transmission is between 20.77% and 40.65% for the selfcollimated lights with frequencies from 0.187c/a to 0.201c/a and thus they form the two partial reflectors. Lights propagate in the FPI utilizing self-collimation effect. The transmission spectrum of the FPI has been investigated with the finite-difference time-domain (FDTD) method. The calculation results show that even slight increase of d can cause peaks shift left to lower frequencies. Through changing the configuration of the reflectors which results in transmission between 19.97% and 38.77%, the varieties of the sharpness of peaks and the degree of extinction of the frequencies between the peaks are obviously observed. Free spectral range (FSR) and peaks frequencies of its transmission decrease when d increases. By raising the reflectivity of the reflectors, the full width at half maximum (FWHM) is decreased and quality (Q) factor of peaks is increased.

An ultra-compact Mach-Zehnder (MZ) electro-optic (EO) modulator composed of nanoscale metal gap waveguides has been numerically demonstrated. Propagations of surface plasmon polaritons (SPPs) in nano-size channels and their EO modulations are investigated by the finite difference time domain (FDTD) method considering the Lorentz-Drude (LD) model. The half-wave voltage (Vπ) of the resulting MZ modulator for push-pull operation is 1.73 V using the interference arm with a sub-micron length (500 nm).

We investigated the enhancement of the voltage-induced phase difference by embedding an electro-optic (EO) polymer into a reflective planar microcavity in a reflection ellipsometric configuration. We fabricated the microcavity with efficient light localization in the EO polymer and evaluated the resultant enhancement of voltage-induced phasedifference between s- and p-polarized components. We obtained 48 times larger phase-difference than that for the EO polymer only. The enhancement was attributed to the polarization-dependent local field effect for oblique incidence.

InP nanowires were grown on InP(100) substrates via VLS mechanism with Au particles as catalyst. Various morphologies of the nanowires such as straight, L-branch, Y-branch, K-branch, bottle-shape, cone-shape, needle-shape were obtained.

KTP planar optical waveguide was fabricated by combining He⁺ ion implantation with Rb-K ion exchange in pure RbNO₃. The lattice damage induced by He⁺ ion implantation and influence of ion implantation on ion exchange waveguide were studied. TRIM'2003 code was used to simulate the process of 2.0 MeV He⁺ ion implantation, the profile of He⁺ ions concentration as well as the defective lattice versus depth were estimated. The dark mode spectra of the waveguide were measured by the prism-coupling method at wavelength 633 and 1539 nm. The refractive index profiles in the novel waveguide were reconstructed by analyzing dark mode spectra and an increased index in the waveguide region together with a decreased index barrier in damaged layer was obtained. The influence of irradiation damage on the Rb distribution was investigated and analyzed by means of RBS technique.

A novel beam splitter is designed on the basis of the coupling characteristics between the waveguide and ring resonator in two dimensional photonic crystals. By simply adjusting the effective refractive index of coupling dielectric rods in the ring resonators symmetrically, inducing the redistribution of the power of the optical field, uniform or free splitting can be achieved. The splitting properties of the beam splitter have been numerically studied using the finite difference time domain (FDTD) method, uniform or free splitting can be achieved. It was shown that a small dimension, a large separating angle, a high beam rate, and has been extended to have more light output channels in the beam splitter. These features of the proposed heterostructure beam splitter make it a promising candidate in optical communications application.

GaAs nanowires were grown by the metal organic chemical vapor deposition on the GaAs(111)B substrates via Vapor- Liquid-Solid mechanism with various Au film thickness. Experiment results indicated that thicker Au film results in larger diameters, more dispersed size distribution, and lower density of the nanowires. All NWs are straight from base to top, and no lateral growth occurs. The growth rate of nanowires slightly increases with Au film thickness. It indicates that the growth of GaAs NWs is mainly promoted by the catalyzed chemical reaction at the drop surface, the Au particles surface density could influence the growth rate, and contribution of diffusion from the adatom could be neglected.

We present an ultra-broadband dispersion measurement method for photonic crystal fiber (PCF) based on Mach-Zehnder interferometer and supercontinuum pulses. A PCF with hole diameter and pitch, 2.17μm and 3.47μm respectively, is measured. The measured dispersion coefficients are well in agreement with the simulation results of the same fiber.

We study the contribution of Surface-plasmons coupling with a single dipole to enhance the emitter emission. When the Ag film is inserted into GaN, the emission efficiency of single dipole in GaN can be enhanced greatly. With 3D-FDTD method, the numerical simulation results demonstrate that the SPs play a key role in enhancement light emitter efficiency. Furthermore, SPs is sensitive not only to the thickness and refractive index of dielectric, but also to the geometry and dispersion model of Ag film. By changing the parameters of GaN and Ag film, the location of the enhancement peak of the emission efficiency in the visible region can be controlled. According to the simply optimal parameters, about 9 times enhancement at 470nm occurs. Our results are of very importance for improving the light-emitting devices of GaN.

The photoluminescence(PL) spectra at room temperature for the Si-based samples doped by Nd, O⁺ by ion implantation are measured. The results show that all the samples possess blue-violet photoluminescence properties under the ultraviolet light excitation and its light emission is stable. The PL spectra has multiple peak structure. The results show the intensity of PL spectra is closely relative to Nd and O⁺ implantation and to the temperature of thermal annealing. The light emission is more greater for the sample of fisrt O⁺ then Nd ion-implanted silicon than the one of first Nd then O⁺ ion-implanted silicon. The light-emitiing mechanism is also analyzed.

Mg-doped AlGaN/GaN superlattice has been grown by metalorganic chemical vapor deposition (MOCVD). Rapid thermal annealing (RTA) treament are carryied out on the samples under nitrogen as protect gas. Hall, photoluminescence (PL), high resolution x-ray diffraction (HRXRD) and atomic-force microscopy (AFM) are used to characterize the electrical, optical and structural properties of the as-grown and annealed samples, respectively. After annealing, the Hall results indicate more Mg acceptors are activated, which leads to higher hole concentration and lower p-type resistivity. The PL intensity of Mg related defect band shows a strong decrease after annealing. The annealing of the superlattice degrade the interface quality of the AlGaN/GaN from the HRXRD results. Many nanometer-grains can be observed on the surface of AlGaN/GaN superlattice from the AFM image. This maybe related with the decomposing of GaN or the separating of Mg from the AlGaN/GaN superlattice.

An approach for Si/Si wafer bonding based on boride-solution treatment was presented. The bonding energy is higher than the Si fracture energy by annealing at 180°C. The properties of the bonded structures were studied in terms of the interface shape, electrical and optical characteristic through scanning electron microscopy (SEM), interface I-V curve, and so on. In this method, the surfaces of two wafers are active by Boride solution, and then following a thermal annealing process. The bonding strength was found to be sufficiently high and could withstand the subsequent etching and polishing procedures of the bonded wafers. This low temperature wafer bonding technology can be used in Optic Electronics Integrated Circuit and this technology with potential to meet a broad range of future telecommunication and computing systems' needs.

In this paper, we design a ultra-short 1×2 1310/1550 nm double-waveguide optical power splitter based on photonic crystal multimode interference. The device can be used to divide the input beam equally for both 1310nm and 1550nm at the same time. The total multimode waveguide length of this device is only about 13 μm, which is one 210th of the conventional dielectric counterparts reported. On the basis of the guided mode propagation analysis method, the self-imaging effect is discussed for the case of symmetric incidence. The finite-difference time-domain method is used to simulate the propagation of the beam in the multimode interference. The results show that the repetitive appearances of single image and twofold image of the input field occur alternatively in this device.

A novel resonant cavity enhanced photodetector with asymmetric dual-absorption layer structures that shifts the limitation on bandwidth-efficiency further than is possible in conventional photodetector is proposed. The quantum efficiency and frequency bandwidth are 93% with a lower reflectivity of top mirror, and 88GHz with mesa area for 10μm×10μm, respectively.

We consider the coupling between four photonic crystal waveguide as a multimode interference system and showed that the dispersion curves of the eigenmodes intersect or almost intersect. Degenerate modes appear in the system. At the crossing point, the multimode interference is deprived and power is confined to its input direction without observable transfering to other photonic crystal waveguides. On the basis of these, a wavelength de-multiplexer or multiplexer is designed.

In 40-Gb/s optical systems, it is impossible to neglect the electronic dispersion of polarization-mode dispersion (PMD). As the data rate is increased, the maximum useful length of the fiber decreases according to the square of the increase. With the development of VLSI and DSP technologies, the electronic dispersion compensation for optical network has aroused greater world attention. In this paper, the performance of decision feedback equalizer (DFE) in PMD-limited 40-GB/s optical links is analyzed by using Matlab/Simulink. A simple equalizer circuit, in fold-cascade traveling-wave filter topology, is presented and the results based on S-parameter simulations show that a DFE equalizer consisting of a 3-tap feed forward equalizer (FFE) and a 2-tap feed back equalizer (FBE) can mitigate PMD effectively.

The absorption spectrum, upconversion spectrum and the fluorescence decay curve of Er³⁺/Yb³⁺ co-doped KY(WO₄)₂ crystal were measured. The radiative transition rates were calculated by Judd-Ofelt theory. A model for the dynamics of frequency upconversion process in Er³⁺/Yb³⁺ co-doped KY(WO4)2 crystal was proposed. The Yb-to-Er energy transfer rate and the upconversion coefficients were estimated by numerically solving the rate equations and fitting simulated curve to the experimental data.

A novel soluble zinc phthalocyanine-bisphenol A epoxy derivative (ZnPc-DGEBPA) was synthesized and characterized by infrared (IR), electronic absorption spectra and fluorescence spectra. Electronic absorption spectrum of ZnPc-DGEBPA exhibited characteristic absorption peaks at 367 nm and 710 nm. Fluorescence emission peak was at 458 nm and quantum yield reached 0.33 in N, N-dimethylformamide (DMF). ZnPc-DGEBPA thin films were prepared by dip-coating technology. Current-voltage characteristics of the films were measured and photoconductivity was increased by an order of magnitude compared with dark conductivity, which indicates the product has excellent film forming ability and good photoelectric response.

In this letter, the spectral characteristics of cotton in the range of 0.2 ~ 2.5THz have been measured with THz timedomain spectroscopy. Its absorption and refraction spectra are obtained at room temperature in nitrogen atmosphere. It is found that cotton has the spectral response to THz waves in this frequency region. The results provided in this paper will help us to study the THz application to cotton commercial transaction inspection further.

200 μm thick free-standing polycrystalline diamond film has been grown by microwave plasma chemical vapor deposition (MPCVD) method. The nucleation surface of diamond is characterized by Raman scattering, scanning electron microscopy (SEM) and atomic force microscopy (AFM) method. AFM and SEM results indicate the nucleation surface is quite smooth with a mean surface roughness (RMS) of about 10 nm. Raman scattering result indicates of high quality nucleation diamond film. A diamond field effect transistor is fabricated on hydrogenated diamond nucleation surface, using standard lithographic procedures. Device with aluminum (Al) gate electrode, to form Schottky barrier with diamond, as well as Au source and drain electrodes to form ohmic contact with diamond, operates as effective enhancement-mode metal-semiconductor field-effect transistors at room temperature, showing clear modulation of channel current.

The optimum parameters' expressions of the lens duct are theoretically deduced with the help of numerical analysis of ray tracing. Based on the theoretical analysis, we simulated the rays' transmission trace in the duct and calculated the intensity distribution of the output beam. The influence of the parameter's value on coupling efficiency is also analyzed in the paper. With the optimum parameters lens duct, we implemented the coupling experiment. A smooth and symmetric beam with high quality is obtained. The coupling efficiency of the lens duct is larger than 91%. The experimental results agree well with the theoretical analysis. More important, the duct's coupling efficiency is better than the results reported previously.