Photonic millimeter-wave generation beyond the cavity thermal limit

Abstract

Next-generation communications, radar, and navigation systems will extend and exploit the higher bandwidth of the millimeter-wave domain for increased communication data rates as well as radar with higher sensitivity and increased spatial resolution. However, realizing these advantages will require the generation of millimeter-wave signals with low phase noise in simple and compact form-factors. Photonic integration addresses this challenge and provides a path toward simplified and portable, low-noise mm-wave generation. We leverage these advances by heterodyning two silicon photonic chip lasers, phase-locked to different axial modes of a miniature Fabry–Perot (F-P) cavity to demonstrate a simple framework for generating low-noise millimeter-waves. By reducing technical noise, we achieve common-mode rejection of the thermally driven Brownian noise such that the millimeter-wave phase noise surpasses that of the thermal limit of a single laser locked to the F-P cavity. This leads to a 118.1 GHz millimeter-wave signal with phase noise of −118dBc/Hz at 10 kHz offset, decreasing to −120dBc/Hz at 30 kHz offset. We achieve this with technologies that can be integrated into a platform less than ≈10mL. Our work overcomes fundamental thermal-mechanical noise limits intrinsic to integrated photonics, while illustrating advantages of the same for providing low-size, -weight, and -power (SWaP) mm-waves that will be enabling for multiple applications in communications and sensing.

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