Shupeng Deng

Bandwidth improvement for germanium photodetector using wire bonding technology

We demonstrate an ultrahigh speed germanium photodetector by introducing gold wires into the discrete ground electrodes with standard wire bonding technology. To engineer the parasitic parameter, the physical dimension of the gold wire used for wire bonding is specially designed with an inductance of about 450 pH. Simulation and experimental results show that the bandwidth of the photodetector can be effectively extended from less than 30 GHz to over 60 GHz.

An SOI based polarization insensitive filter for all-optical clock recovery.

We propose and fabricate an SOI based polarization diversity scheme consisting of two 2D grating couplers and a micro ring resonator. Based on this scheme, all-optical polarization insensitive clock recovery has been demonstrated successfully.

Ultra efficient silicon nitride grating coupler with bottom grating reflector.

We theoretically propose a silicon nitride (Si(3)N(4)) grating coupler (GC) with both ultrahigh efficiency and simplified fabrication processes. Instead of using a bottom distributed Bragg reflector (DBR) or metal reflector, a bottom Si grating reflector (GR) with comparable reflectivity is utilized to improve the coupling efficiency. The fully etched Si GR is designed based on an industrially standard silicon-on-insulator (SOI) wafer with 220 nm top Si layer. By properly adjusting the trench width and period length of the Si GR, a high reflectivity over 90% is obtained. The Si(3)N(4) GC is optimized based on a common 400 nm Si(3)N(4) layer sitting on the Si GR with a SiO(2) separation layer. With an appropriate distance between the Si(3)N(4) GC and bottom Si GR, a low coupling loss of -1.47 dB is theoretically obtained using uniform GC structure. A further record ultralow loss of -0.88 dB is predicted by apodizing the Si(3)N(4) GC. The specific fabrication processes and tolerance are also investigated. Compared with DBR, the bottom Si GR can be easily fabricated by single step of patterning and etching, simplifying the fabrication processes.

Short and efficient mode-size converter designed by segmented-stepwise method.

We present an efficient segmented-stepwise method to design a short and low-loss mode-size converter. A silicon-on-insulator platform-based converter with 20 μm length and 95.2% conversion efficiency is acquired by taking only 10 optimization generations using 2D-FDTD method. A 3D-FDTD simulation is performed to verify the calculated results, returning an efficiency of 92.1%. The proposed device can be used to connect a 12-μm-wide waveguide and a 0.5-μm-wide single-mode waveguide, with comparable performance of a regular scheme using 150-μm-long linear taper. For demonstration, the converter was fabricated by electron-beam-lithography and inductively-coupled-plasma etching. A conversion loss of -0.62±0.02  dB at 1550 nm was experimentally measured.

Silicon IQ Modulator for Next-Generation Metro Network

Silicon photonics have been extensively demonstrated as the promising solution for low-cost and high-performance transmission network. We show that silicon Mach-Zehnder IQ modulators are capable for next-generation metro network applications. The transmission distances cover whole metro transmission range, up to 960 km. We experimentally demonstrated different modulation formats for different scenarios with these modulators. For 320-km transmission, 56 Gb/s single-sideband discrete multitone transmission was achieved. For 480 km, 80 × 453.2-Gb/s polarization division multiplexing (PDM) orthogonal frequency-division multiplexing hybrid 8-64 quadrature amplitude modulation (QAM) dense wavelength division multiplexing signals transmission was achieved. Finally, 80 × 337.9-Gb/s transmission of Nyquist-WDM PDM-16QAM was achieved for 960 km.

Optimized 32-channel silicon hybrid demultiplexer fabricated with CMOS technology

We presented a 32-channel silicon hybrid demultiplexer fabricated with CMOS technology. Double-etched mode converter and wide arrayed waveguide are used to improve AWG performances while the counter-tapered coupler is optimized for broadband mode multiplexing.

A four-port polarization diversity coupler for vertical fiber-chip coupling

We propose and fabricate a novel four-port polarization diversity coupler for vertical coupling. With the help of 45° reflectors and improved 2×1 couplers, an ultralow coupling loss of -4.8dB is experimentally measured with polarization insensitivity.