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arXiv · 2505.14956

From ultra-noisy to ultra-stable: optimization of the optoelectronic laser lock

Takuma Nakamura·Yifan Liu·Naijun Jin·Haotian Cheng·Charles McLemore·Nazanin Hoghooghi·Peter Rakich·Franklyn Quinlan
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Abstract

We demonstrate thermal-noise-limited direct locking of a semiconductor distributed feedback (DFB) laser to a sub-1 mL volume, ultrastable optical cavity, enabling extremely compact and simple ultrastable laser systems. Using the optoelectronic laser locking method, we realize over 140 dB suppression of the DFB free-running laser noise at 10 Hz offset, a level we estimate to be ~ 70 dB greater than Pound-Drever-Hall locking can provide, and reach a phase noise level of -120 dBc/Hz at 200 kHz offset. We also demonstrate a new feedforward noise correction method that improves the quality of the heterodyne beat with an optical frequency comb by providing another 60 dB of laser noise rejection - a level that is 15 dB greater than predicted by current models. With feedforward, we transfer the cavity thermal noise limit across the comb spectrum despite the fact that the cavity-locked laser itself is noisy. These results establish a simple, low noise, compact approach to ultrastable laser locking that is compatible with integrated photonics, with applications in low phase noise microwave generation, sensing, and satellite ranging.

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Takuma Nakamura, Yifan Liu, Naijun Jin, Haotian Cheng, Charles McLemore, Nazanin Hoghooghi, Peter Rakich, Franklyn Quinlan. 2025-05-20. From ultra-noisy to ultra-stable: optimization of the optoelectronic laser lock. https://doi.org/10.1063/5.0297890

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