Steven M. Zhu | Searcharxiv

arXiv2026

Heterogeneously Integrated Balanced Photodetector on an Ultra-Low Loss Silicon Nitride Delay Line Interferometer

Thin core silicon nitride photonics enables ultra-low loss, CMOS foundry compatible integration that supports wavelengths from the visible to shortwave infrared. Applications that can benefit from the resulting lower cost, improved robustness, and portability include quantum sensing and computing, ultra-low noise microwave generation, optical clocks, optical gyros, coherent fiber communications, and fiber sensing. An important next step is integration of functional circuits and systems on chip with heterogeneous integration of active components such as high-performance photodetection. Yet to date integrated high-performance photodetectors on the thin film silicon nitride platform has remained elusive. In this work, we demonstrate heterogeneous integration of an InGaAs on InP substrate Modified Uni-Traveling Carrier balanced photodetector with a 15-meter-long unbalanced thin core silicon nitride Mach-Zehnder Interferometer with a bandwidth of 0.92 GHz and a responsivity of 0.305 A/W at 1550 nm with a propagation loss as low as 2.5 dB/m at 1600 nm. Using this circuit we demonstrate two functions, a meter-scale differential interferometer laser stabilization circuit achieving a nearly 23 dB noise suppression at 1 kHz offset and an optical frequency discriminator frequency noise measurement with high sensitivity across 6 orders of magnitude from 10 Hz to 10 MHz. These results demonstrate that the high performance of thin core silicon nitride devices can be combined with integrated high-performance photodetection to realize on-chip stabilized lasers and circuits and pave the path towards full systems on chip.

physics.optics↗

arXiv2025

Integrated Architecture for the Automated Generation and Coil Stabilization of a PZT-Enabled Microcomb

Silicon nitride Dissipative Kerr Soliton (DKS) microcombs have emerged as a future solution to bring metrological optical frequency comb capabilities into a photonic integrated platform with mass-scale fabrication benefits. Precision applications demand low comb line phase noise as well as high repetition rate stability, but current approaches to achieve this involve complex architectures, multiple lasers, and high-power components, which are challenging to integrate to the chip scale. To achieve this goal, new architectures are needed to simplify the comb generation, actuation, and pump laser requirements, while enabling chip-integrated solutions. Here we demonstrate a greatly simplified stabilized DKS comb architecture with a single laser and a single point electronic control of both the microcomb generation and its stabilization to a coil-resonator reference. The silicon nitride microcomb is integrated with a low power, broadband PZT actuator that is driven by a simple electronic control sequence that generates a soliton and stabilizes it to the 16-meter silicon nitride coil resonator. PZT-enabled control brings flexibility and simplicity to the soliton generation and stabilization using a single CW pump laser, resulting in significantly reduced electronic and optical infrastructure. We demonstrate coil-resonator locking which suppresses the 1 kHz frequency noise by 40 dB over the 35 nm wide comb spectrum, with comb line linewidths as low as 66 Hz and 108 GHz soliton repetition rate phase noise equivalent to -118 dBc/Hz when divided down to 10 GHz. The low power PZT actuator consumes nW bias power and the coil resonator allows flexible dual locking using arbitrary comb lines. These results show a clear path towards full chip integration of stabilized soliton microcombs with simplicity and versatility absent in other schemes.

physics.optics↗