Foundry-Enabled High-Power Photodetectors and Micro-Transfer Printable Mach-Zehnder Modulator for Microwave Photonic Applications

Tzu, Ta-Ching, Electrical Engineering - School of Engineering and Applied Science, University of Virginia
Beling, Andreas, EN-Elec & Comp Engr Dept, University of Virginia

Integrated microwave photonics is being considered the next cornerstone for reducing size, weight, and power (SWaP) in next generation microwave photonic systems. To realize an integrated microwave photonic system, CMOS-compatible and heterogeneously integrated III-V-on-silicon photonic platforms are two promising approaches that have been developed over the past decade based on the growing maturity of advanced semiconductor fabrication technology in photonics. Since high-speed photodetectors and modulators are key components inside a microwave photonic system, significant research has been devoted recently on developing fully integrated photodetectors and modulators on Si and other photonic platforms. This to be the research motivation, my dissertation is structured into three main topics: (1) high-power arrayed photodetector, traveling-wave photodetector, and group array photodetector combiner enabled by a silicon foundry platform for microwave photonic applications, (2) micro-transfer printable InP-based O-band multi-quantum well Mach-Zehnder modulator, and (3) heterogeneously integrated III-V-on-silicon distributed array photodetector.

In the first part of my work, an 8-element photodetector array with a record-high 14.3 dBm RF output power at 5 GHz has been demonstrated using AIM Photonics foundry. To expand the bandwidth and overcome the resistance-capacitance (RC) bandwidth limitation, I developed a new traveling-wave photodetector with integrated biasing circuit with 32 GHz bandwidth and 6 dBm output power at 44 mA photocurrent. An integrated 20 GHz receiver based on a pair of balanced photodiodes and a Mach-Zehnder delay line interferometer was also successfully demonstrated in an optical phase-modulated link. Balanced photodiodes are a vital component in some analog photonic links to suppress common mode noise, and a novel balanced traveling-wave photodetector with fully integrated biasing circuit was introduced to improve the radio frequency (RF) performance demonstrating a 25 GHz bandwidth and 30 dB common mode rejection ratio. Finally, a new 32-PD fully distributed group array photodetector combiner has been demonstrated with 15 GHz bandwidth which can be used as a massive RF power combiner inside a microwave photonic system. Also, I developed a balanced type of the group array photodetector combiner with 13 GHz bandwidth and 30 dB common mode rejection ratio.

In the second part of my work, I report a > 67 GHz bandwidth InP-based transfer printable multi-quantum well Mach-Zehnder modulator (MZM) with 17 dB extinction ratio at 1310 nm wavelength. A clear 40 Gbps optical eye diagram is presented to show its large signal modulation ability. To the best of my knowledge, this is the first high-speed multi-quantum well MZM for 1310 nm wavelength that has been reported. In this work, I have designed the undercut insensitive multimode interference coupler, and adapted the concept to the modulator fabrication process development. ~ 1dB excess loss was achieved. Finally, initial results from transfer-printed modulators on a SiN photonic platform are reported with measurement results and process flow analysis.

In the final part of my work which will be continued as the future work, I used heterogeneously integrated uni-traveling carrier photodiodes to develop a group array photodetector combiner with improved RF output power. Design and simulated RF performance of the device are presented in this work followed by initial device fabrication, measurement results and analysis.

PHD (Doctor of Philosophy)
Silicon photonics, Photodetector, Optoelectronics
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