Jiarui Fei

High-reflectivity high-contrast grating focusing reflector on silicon-on-insulator wafer

A high-contrast grating (HCG) focusing reflector providing phase front control of reflected light and high reflectivity is proposed and fabricated. Basic design rules to engineer this category of structures are given in detail. A 1550 nm TM polarized incident light of 11.86 mm in focal length and 0.8320 in reflectivity is obtained in experiment. The wavelength dependence of the fabricated HCGs from 1530 nm to 1580 nm is also tested. The test results show that the focal length is in the range of 11.81–12 mm, which is close to the designed focal length of 15 mm. The reflectivity is almost above 0.56 within a bandwidth of 50 nm. At a distance of 11.86 mm, the light is focused to a round spot with the highest concentration, which is much smaller than the size of the incident beam. The FWHM of the reflected light beam decreases to 120 nm, and the intensity increases to 1.18.

Transient simulation of UTC-PD using drift-diffusion model

In this paper, the reliability of transient simulation results of uni-traveling-carrier photodiodes (UTC-PDs) is demonstrated by compared with experimental and reported simulation results, when the parameters of drift-diffusion model are set correctly.

Design and optimization of photodetector array electrodes

We designed and optimized a high-speed, low-loss electrodes applied to photodetector array (PDA) using simulating software HFSS. The designed electrodes structure was fabricated and tested. Compared with the electrodes before optimization, the insert loss decreased by 1.1dB at 40GHz and the bandwidth increased by 8GHz.

Association analysis of nonlinear saturation characteristics based on high-speed and high-output photodetectors

With the development of optical communication system, the nonlinear saturation characteristics of photodetectors are necessary to consider. We observed the 1-dB compression current as DC photocurrent saturation point under high power illumination in PIN-PDs. Meanwhile, a new method of measuring AC saturated output power in the time domain is proposed. The quantitative relationship between DC saturation point and AC saturation point is given.

Using time-domain transient simulation to characterize nonlinear intermodulation distortions in photodetectors

We propose a universal simulating solution to characterize the OIP3 of most kinds of photodetectors using Silvaco TCAD simulation tools. For a normal PIN photodetector and a unitraveling-carrier photodetector, a fine agreement was observed in experimental results and simulation results. We believe that this solution could be useful in designing and optimizing high-power photodetectors.

High-power symmetric-connected uni-traveling-carrier photodiode array integrated with sub-wavelength gratings based beam-splitter

We present a two-element back-illuminated symmetric-connected uni-traveling-carrier photodiode array (SC-PDA) integrated with sub-wavelength-gratings based beam-splitter (SWGs-BS) for high power optoelectronic applications. The SC-PDA with SWGs-BS, a top-illuminated SC-PDA and a single PD were fabricated and tested. The proposed SC-PDA with SWGs-BS demonstrates a 3dB bandwidth of 23.8GHz@60mA, a saturation current of 87.9mA@12GHz and a maximum output RF power of ~16dBm@12GHz. Compared to the top-illuminated SC-PDA and the single PD, the proposed SC-PDA with SWGs-BS achieved high-power handling capability at low coupling complexity and requires no phase-matching techniques in the system.

Monolithic Symmetric-Connected Photodiode Array

We demonstrate a two-element symmetric-connected photodiode array (SC-PDA) for high-power and high-speed applications. A traditional traveling-wave photodiode array (TW-PDA), an SC-PDA, and a single PD with the same epitaxial structure were fabricated and tested. Both the TW-PDA and SC-PDA have higher saturation currents, larger RF power, and better high-power and high-frequency responses than the single PD. However, the results show that the SC-PDA has a higher responsivity (0.32 A/W), a smooth frequency response (14.0 GHz), and a higher saturation current (66 mA) than the TW-PDA (0.24 A/W, periodically patterned frequency response and 42 mA) without using phase matching techniques.

Polarization I nsensitive B eam S plitter W ith F ocusing A bility U sing 2D H igh I ndex C ontrast G ratings

A polarization-insensitive 2D high index contrast gratings (HCGs) beam splitter based on silicon-on-insulator(SOI) is proposed and demonstrated, which performs two independent functions: transmission focusing and power equalization at the wavelength of 1550 nm.