Jasper de Graaf

The fast-maturing photonic integration technology is calling for a versatile platform that supports both active and passive functions as well as high scalability through component miniaturization. Indium phosphide (InP) has long been recognized for its ability to deliver a comprehensive suite of photonic components. InP membrane technology has emerged as a next-generation solution that could unite the functional completeness with high scalability. This paper describes recent advancements in the InP-membrane-on-Si (IMOS) platform, which supports high-performance passives, polarization and mode handling, native light sources, amplifiers, modulators and detectors, and novel material integration.

This work presents two circuit-based solutions to enhance the power handling capabilities of waveguide-integrated uni-travelling carrier photodetectors (WG-UTC-PDs). Compared to a baseline WG-UTC-PD, these solutions achieve a fivefold increase in photocurrent before thermal breakdown. First, dual-injection improves the optical power distribution within a baseline WG-UTC-PD, raising the photocurrent threshold before thermal breakdown. Second, an array of four optically parallel WG-UTC-PDs, electrically connected to a single coplanar waveguide (CPW) line, further increases the maximum photocurrent by distributing the input optical power across multiple PDs. The design omits a termination resistor, as the arrays do not rely on a traveling wave configuration, maximizing photocurrent without a 50% reduction of bandwidth. Both 4-PD single-injection and dual-injection arrays were designed, fabricated, and characterized. Compared to a baseline UTC-PD, with a maximum photocurrent of 1.8 mA at a 3 dB bandwidth of 55 GHz, the 4-PD single-injection circuit achieved 5.1 mA at 43 GHz. The dual-injection array further increased the photocurrent to 9.2 mA at a bandwidth of 35 GHz. Electrical reflection measurements confirmed the negative effects of CPW losses on RF performance. These power handling improvements enable compact, high-power integrated solutions for microwave photonics.

In this work we have demonstrated a waveguide integrated uni-traveling carrier photodiode on an InP-membrane-on-silicon platform with 3 dB bandwidth beyond 110 GHz. With design optimization and an improved process, devices as small as $ \text{3}\times \text{2}\;\mu \text{m}^2$ are successfully realized. An electrical equivalent circuit model based on measured S-parameters revealed ultra-small series resistance and junction capacitance as low as 6.5 $\Omega$ and 4.4 fF, respectively, in the diodes. The model also provided insight in the photocurrent dependent characteristics in the bandwidth and resonsivity of the devices. Finally, data transmission measurements are demonstrated, showcasing the high speed telecommunication abilities of the UTC-PD.