Photonic integration is one of the most important issues in scientific research. Silicon-on-insulator (SOI) and other materials play an important role in photonic integration, but their losses are large and affect the integration, so it is very important to find new waveguide materials. As a consequence, Si3N4 came into being and is now a hot area of research. Its crystal structure is stable, with a wide energy band of Eg~5.1 eV, so it is transparent in the whole optical range from ultraviolet to infrared. Also, its optical loss in this range is very low, α~0.045±0.04 dB/m, which is lower than that of SOI waveguides by 3—4 orders of magnitude. Its refractive index at 1550 nm is ~2, so combined with Si and SiO2, high-performance dielectric waveguide structures can be designed. Its thermal expansion coefficient is ~2.35×10-6/℃, smaller than that of Si, so its growth on Si will introduce a larger tensile stress and may produce cracks. Thus, growing thick films of large area is very difficult. By using low-pressure or plasma-enhanced chemical vapor deposition, Si3N4 films can be deposited on low refractive index SiO2 to form Si3N4-SiO2 waveguides, which are smaller in size and allow better integration. Current research progress in this field is reviewed, and future application prospects are reviewed.

硅基光互连技术是解决目前电互连制约瓶颈的有效手段, 而实用化集成光源的制备对硅基芯片功耗的降低和尺寸的减小有着十分重要的意义。硅基集成激光器在过去的十多年间取得了一系列重要突破, 其中III-V/Si混合集成激光器是近期最可能获得实际应用的方案之一。文章简要分析了硅基集成激光器的研究现状, 重点介绍了III-V/Si混合集成激光器的研究进展, 包括III-V/Si键合激光器和III-V/Si倒装焊激光器的发展和各自存在的问题, 并预测了硅基集成激光器的发展方向。

We demonstrate a sub-nanosecond electro-optical switch with low crosstalk in a silicon-on-insulator (SOI) dual-coupled micro-ring embedded with p-i-n diodes. A crosstalk of -23 dB is obtained in the 20 \mu m-radius micro-ring with the well-designing asymmetric dual-coupling structure. By optimizations of the doping profiles and the fabrication processes, the sub-nanosecond switch-on/off time of <400 ps is finally realized under an electrical pre-emphasized driving signal. This compact and fast-response micro-ring switch, which can be fabricated by complementary metal oxide semiconductor (CMOS) compatible technologies, have enormous potential in optical interconnects of multicore networks-on-chip.

Pure Ge is grown on Si substrate to control the release of the strain in the heterostructure, which is due to the 4.2% lattice misfit between Ge and Si. In this letter, an innovative approach of multi-buffer layers is proposed for the epitaxial growth of high quality Ge thin films on Si (001) substrates in a molecular beam epitaxy system. The multi-buffer layers, including the low temperature Ge seed layer and the Si-Ge alloy intermediate layer fabricated under different temperatures, serve as defect gathering and annihilating sites to reduce the dislocation density in the top layers. The result reveals that the total thickness of the whole structure is less than 400 nm, with a low threading dislocation density of less than 5×10⁵ cm^-2 in the top layer and a root mean square surface roughness of 1.5 nm.

本文设计并制作了基于强限制多模干涉耦合器的2×2 SOI马赫-曾德热光开关.这种光开关采用了深刻蚀结构的多模干涉耦合器和输入/输出波导,较大地提高了干涉耦合器的性能并减少了连接耦合损耗.同时,在调制臂区域采用浅刻蚀结构,保持其单模调制状态.深刻蚀多模干涉耦合器具有优越的特性,在实验中测得不均衡度只有0.03 dB,插入损耗-0.6 dB.基于这种耦合器的新型热光开关,其插入损耗为-6.8 dB,其中包括光纤-波导耦合损耗-4.3 dB,开关时间为6.8 μs.

根据马赫-曾德尔型热光开关的工作原理,提出了可以提高热光开关响应速度的过驱动方法并设计相应的驱动电路,使SOI 4×4 重排无阻塞热光开关阵列的响应时间从大于2 ms提高到了亚微秒。

A 3-dB paired interference (PI) optical coupler in silicon-on-insulator (SOI) based on rib waveguides with trapezoidal cross section was designed with simulation by a modified finite-difference beam propagation method (FD-BPM) and fabricated by potassium hydroxide (KOH) anisotropic chemical wet etching. Theoretically, tolerances of width, length, and port distance are more than 1, 100, and 1 microns, respectively. Smooth interface was obtained with the propagation loss of 1.1 dB/cm at the wavelength of 1.55 microns. The coupler has a good uniformity of 0.2 dB and low excess loss of less than 2 dB.

利用高阶Pade近似的2D－BPM算法，对具有不同弯曲半径及交叉角度的SOI弯曲交叉波导的传输特性进行了模拟、分析和深入研究，发现交叉波导的串扰随弯曲半径及交叉角度增大而减小的规律．在此基础上，对由正弦弯曲、余弦弯曲以及圆弧弯曲三种弯曲波导构成的SOI交叉波导的损耗及串扰特性进行了分析比较．结果表明，由正弦弯曲构成的交叉波导传输损耗最小且串扰最小．