Recent progresses of SOI-based photonic devices - art. no. 60201R

SOI (Silicon on Insulator) based photonic devices, including stimulated emission from Si diode, RCE (Resonant Cavity Enhanced) photodiode with quantum structure, MOS (Metal Oxide Semiconductor) optical modulator with high frequency, SOI optical matrix switch and wavelength tunable filter are reviewed in the paper. The emphasis will be played on our recent results of SOI-based thermo-optic waveguide matrix switch with low insertion loss and fast response. A folding re-arrangeable non-blocking 4x4 matrix switch with total internal reflection (TIR) mirrors and a first blocking 16 x 16 matrix were fabricated on SOI wafer. The extinction ratio and the crosstalk are better. The insertion loss and the polarization dependent loss (PDL) at 1.55 mu m increase slightly with longer device length and more bend and intersecting waveguides. The insertion losses are expected to decrease 2-3 dB when anti-reflection films are added in the ends of the devices. The rise and fall times of the devices are 2.1 mu s and 2.3 mu s, respectively.

Subtraction of S-parameters for adiabatic small-signal modulation characteristics of laser diode - art. no. 60201V

An extended subtraction method of scattering parameters for characterizing laser diode is introduced in this paper. The intrinsic small-signal response can be directly extracted from the measured transmission coefficients of laser diode by the method. However the chip temperature may change with the injection bias current due to thermal effects, which causes inaccurate intrinsic response by our method. Therefore, how to determine the chip temperature and keep the laser chip adiabatic is very critical when extracting the intrinsic response. To tackle these problems, the dependence of the lasing wavelength of the laser diode on the chip temperature is investigated, and an applicable measurement setup which keeps the chip temperature stable is presented. The scattering parameters of laser diode are measured on diabatic and adiabatic conditions, and the extracted intrinsic responses for both conditions are compared. It is found that the adiabatic intrinsic responses are evidently superior to those without thermal consideration. The analysis indicates that inclusion of thermal effects is necessary to acquire accurate intrinsic response.

Leakage current analysis in AlGaInP/GaInP multi-quantum well lasers by the electrical derivative method - art. no. 60202F

In AlGaInP/GaInP multi-quantum well (MQW) lasers, the electron leakage current is a much more serious problem than that in laser diodes with longer wavelength. To further improve the output performance, the leakage current should be analyzed. In this letter, the temperature dependence of electrical derivative characteristics in AlGaInP/GaInP multi-quantum well lasers was measured, and the potential barrier for electron leakage was obtained. With the help of secondary ion mass spectroscopy (SIMS) measurement, theoretical analysis of the potential barrier was presented and compared with the measurement result. The influence of p-cladding doping level and doping profile on the potential barrier was discussed, and this can be helpful in metalorganic chemical vapor deposition (MOCVD) growth.

Influence of dispersive coupling coefficient in microring channel drop filters

Wide transmission dips are observed in the through spectra in microring and racetrack channel drop filters by two-dimensional finite-difference time-domain (FDTD) simulation. The transmission spectra, which reflect the coupling efficiency, are also calculated from the FDTD output as the pulse just travels one circle inside the resonator. The results indicate that the dips are caused by the dispersion of the coupling coefficient between the input waveguide and the resonator. In addition, a near-zero channel drop on resonance and a large channel drop off resonance are observed due to the near zero coupling coefficient and a large coupling coefficient, respectively. If the width of the input waveguide is different from that of the ring resonator, the oscillation of the coupling coefficient can be greatly suppressed.

Small-signal and large-signal performance test of high-speed optoelectronics devices

This paper presents measurement methods for determining the reflection coefficients and frequency responses of semiconductor laser diodes, photodiodes, and EA modulator chips. A novel method for determining the intrinsic frequency responses of laser diodes is also proposed, and applications of the developed measurement methods are discussed. We demonstrate the compensation of bonding wire on the capacitances of both the submount and the laser diode, and present a method for estimating the potential modulation bandwidth of TO packaging technique. Initial study on removing the effects of test fixture on large-signal performances of optoelectronic devices at high data rate is also given.

Theoretical analysis of the bandgap for the intermixed GaInP/AlGaInP quantum wells

Compositional distribution of the quantum well and barrier after quantum well intermixing for GaInP/AlGaInP system was theoretically analyzed on the basis of atom diffusion law. With the compositional distribution result, the valence subband structure of the intermixed quantum well was calculated on the basis of 6x6 Luttinger-Kohn Hamiltonian, including spin-orbit splitting effects. TO get more accurate results in the calculation, a full 6-band problem was solved without axial approximation, which had been widely used in the Luttinger-Kohn model to simplify the computational efforts, since there was a strong warping in the GaInP valence band. At last, the bandgap energy of the intermixed quantum well was obtained and the calculation result is of much importance in the analysis of quantum well intermixing experiments.

Calculation of valence subband structures for strained GaInP/AlGaInP quantum wells without axial approximation

Usually in the calculation of valence subband structure for III-V direct bandgap material, axial approximation had been used in the Luttinger-Kohn model to simplify the computational efforts. In this letter, the valence subband structure for the GaInP/AlGaInP strained and lattice-matched quantum wells was calculated without axial approximation, on the basis of 6x6 Luttinger-Kohn Hamiltonian including strain and spin-orbit splitting effects. The numerical simulation results were presented with help of the finite-difference methods. The calculation results with/without axial approximation were compared and the effect of axial approximation on the valence subband structure was discussed in detail. The results indicated that there was a strong warping in the GaInP valence band, and axial approximation can lead to an error when k was not equal to zero, especially for compressively strained and lattice-matched GaInP/AlGaInP quantum wells.

Influence of mode symmetry on quality factors of degenerate states in microlasers with an equilateral triangle resonator

Modes in equilateral triangle resonator (ETR) are analyzed and classified according to the irreducible representations of the point group C-3v., Both the analytical method based on the far field emission and the numerical method by FDTD technique are used to calculate the quality factors (Q-factors) of the doubly degenerate states in ETR. Results obtained from the two methods are in reasonable agreement. Considering the different symmetry properties of the doubly degenerate eigenstates, we also discuss the ETR joined with an output waveguide at one of the vertices by FDTD technique and the Pade approximation. The variation of Q-factors versus width of output waveguide is analyzed. The numerical results show that doubly degenerate eigenstates of TM0.36 and TM0.38 whose wavelengths are around 1.5 mu m in the resonator with side-length of 5 mu m have the Q-factors larger than 1000 when the width of the output waveguide is smaller than 0.4 mu m. When the width of the output waveguide is set to 0.3 mu m, the symmetrical states that are more efficiently coupled to output waveguide have Q-factors about 8000, which are over 3 times larger than those of asymmetric state.

Long-wavelength SiGe/Si MQW resonant-cavity-enhanced photodetectors (RCE-PD) for application in optical fiber communication network

　

MOCVD growth of high quality crack-free GaN on Si(III) substrates

High quality crack free GaN epilayers were grown on Si(111) substrates. Low temperature AlN interlayer grown under low V/III ratio was used to effectively eliminate the formation of micro-cracks. It is found that tensile stress in the GaN epilayer decreases as the N/Al ratio decreases used for AlN interlayer growth. The high optical and structural qualities of the GaN/Si samples were characterized by RBS, PL and XRD measurements. The RT-PL FWHM of the band edge emission is only 39.5meV The XRD FWHM of the GaN/Si sample is 8.2arcmin, which is among the best values ever reported.

Fabrication of semiconductor optical amplifiers and a novel gain measuring technique

The design and fabrication of 1550 nm semiconductor optical amplifiers (SOAs) and the characteristics of the fabricated SOA are reported. A novel gain measurement technique based on the integrations of the product of emission spectrum and a phase function over one mode interval is proposed for Fabry-Perot semiconductor lasers.

MMI optical couplers and switches with SOI technology

MMI (multimode interference) coupler, modulator and switch based on SOI (silicon- on-insulator) have been become more and more attractive in optical systems since they show important performances. SiO2 thin cladding layers (<1.0mum) can be used in SOI waveguide due to the large index step between Si and SiO2, making them compatible with the VLSI technology. The design and fabrication of multimode interference (MMI) optical coupler, modulator and switche in SOI technology are presented in the paper. The results demonstrated that the modulator has an extinction ratio of -11.0dB and excess loss of -2.5dB, while the optical switch has a crosstalk of -12.5dB and responding time of less than 20 mus.

16-channel VCSEL based multiple chip modules

　

Wavelength tunable electroabsorption modulated DFB baser with thin film heater

　

五种天然低聚糖及其硫酸酯衍生物抗病毒活性研究

本文直接针对当前严重的世界性问题－病毒传染性疾病，开展了五种天然低聚糖及其硫酸酯衍生物的制备、抗病毒活性研究以及具抗疱疹病毒活性低聚糖硫酸酯作用机制的初步探讨。中药的结构修饰是中药现代化的重要内容，本研究的开展结合了药学、药理学和构效学，进一步丰富了硫酸酯化糖类抗病毒活性研究，有助于获得抗病毒活性新型药物以用于病毒引起的各类疾病，具有重要的理论和应用意义。1。分别从多花黄精以及与之在种属上有着由近及远关系的大玉竹、天冬、魔芋（酶解干粉）和香菇（子实体）中用类似程序提取了五种低聚糖样品，分别命名为Pcos、Pmos、Acos、Apkos、Leos。单糖组成分析、凝胶柱层析、红外光谱分析以及基体辅助激光解吸-飞行时间质谱分析的结果表明五种样品属于分子量比较接近、单糖组成各异、糖链骨架结构不同的低聚糖。这为后面不同糖链骨架结构的低聚糖硫酸酯的制备、探讨低聚糖硫酸酯衍生物糖链结构与抗病毒活性的关系建立了基础。从香菇子实体中用酶法制备低糖为首次报道。2。采用氯磺酸-吡啶法分别制备了五种天然低聚会糖的硫酸酯衍生物，分别命名为S-Pcos、S-Pmos、S-Acos、S-Apkos、S-Leos，经硫含量分析、Biol-Gel P4 凝胶柱层析、红外光谱分析证明该方法成功地向低聚糖中引入了硫酸基团，为开展天然低聚糖及其硫酸酯的抗病毒活性研究准备了必备的材料。3。利用细胞病变抑制法、中性红染色法、病毒空斑抑制法开展了五种低聚糖及其硫酸酯的体外抗HSV-2活性研究，结果都表明五种天然低聚糖本身没有抗HSV-2活性，除S-Acos之外的四种不同糖链骨架结构的低聚糖硫酸酯产生大小不同的活性， 说明硫酸酯低聚糖的抗病毒活性具有普遍的意义，这就大大扩大了药源，也为新的抗病毒活性药物筛选提供了新的思路和途径。S-Acos没有抗HSV-2活性，可能是因为低聚糖硫酸酯的抗病毒活性还存在硫酸基团以外的其它因素在起作用。五种低聚糖硫酸酯能抑制乙型肝炎抗原表达，说明低聚糖硫酸酯可能具有广谱抗病毒活性，有很大的应用前景。大玉竹、天冬、魔芋低聚糖及其硫酸酯的抗病毒活性研究未见报道。四种具抗HSV-2活性的低聚糖硫酸酯中，以S-Pmos的抗HSV-2活性最好，具有潜在抗病毒药物开发应用价值，值得进一步研究开发。4。初步探讨了低聚糖硫酸酯的抗病毒作用机制，由不同时间加药实验结果推测四种低聚糖硫酸硫酯具有类似的作用机制，可能作用于HSV-2与细胞的吸附阶段，不能抑制病毒在细胞内的复制过程；低聚糖硫酸酯的作用对象为病毒；对病毒毒力的影响实验和撤药实验说明四种低聚硫酸酯不能杀灭HSV-2，仅起抑制作用。作用机制的研究不仅进一步明确了四种低聚糖硫酸酯的抗HSV-2活性，还为今后开发和临床应用该类潜在性抗病毒药物提供了实验基础和依据。