Ultralow-noise frequency-agile photonic integrated lasers

Grigory Lihachev; Johann Riemensberger; Wenle Weng; Junqiu Liu; Hao Tian; Anat Siddharth; Viacheslav Snigirev; Rui Ning Wang; Jijun He; Sunil A. Bhave; Tobias J. Kippenberg

arXiv · 2104.02990

Ultralow-noise frequency-agile photonic integrated lasers

Grigory Lihachev·Johann Riemensberger·Wenle Weng·Junqiu Liu·Hao Tian·Anat Siddharth·Viacheslav Snigirev·Rui Ning Wang·Jijun He·Sunil A. Bhave·Tobias J. Kippenberg

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Abstract

Low-noise lasers are of central importance in a wide variety of applications, including high spectral-efficiency coherent communication protocols, distributed fibre sensing, and long distance coherent LiDAR. In addition to low phase noise, frequency agility, that is, the ability to achieve high-bandwidth actuation of the laser frequency, is imperative for triangular chirping in frequency-modulated continuous-wave (FMCW) based ranging or any optical phase locking as routinely used in metrology. While integrated silicon-based lasers have experienced major advances and are now employed on a commercial scale in data centers, integrated lasers with sub-100 Hz-level intrinsic linewidth are based on optical feedback from photonic circuits that lack frequency agility. Here, we demonstrate a wafer-scale-manufacturing-compatible hybrid photonic integrated laser that exhibits ultralow intrinsic linewidth of 25 Hz while offering unsurpassed megahertz actuation bandwidth, with a tuning range larger than 1 GHz. Our approach uses ultralow-loss (1 dB/m) Si$_3$N$_4$ photonic microresonators, combined with aluminium nitride (AlN) or lead zirconium titanate (PZT) microelectromechanical systems (MEMS) based stress-optic actuation. Electrically driven low-phase noise lasing is attained by self-injection locking of an Indium Phosphide (InP) laser chip and only limited by fundamental thermo-refractive noise. By utilizing difference drive and apodization of the photonic chip, a flat actuation response up to 10 MHz is achieved. We leverage this capability to demonstrate a compact coherent LiDAR engine that can generate up to 800 kHz FMCW triangular optical chirp signals, requiring neither any active linearization nor predistortion compensation, and perform a 10 m optical ranging experiment, with a resolution of 12.5 cm.

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Grigory Lihachev, Johann Riemensberger, Wenle Weng, Junqiu Liu, Hao Tian, Anat Siddharth, Viacheslav Snigirev, Rui Ning Wang, Jijun He, Sunil A. Bhave, Tobias J. Kippenberg. 2021-07-15. Ultralow-noise frequency-agile photonic integrated lasers. https://arxiv.org/abs/2104.02990

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