Widely Tunable Heterodyne mm-Wave Signal Generation Based on SIL and PDH

Photonic millimeter-wave (mm-wave) signal generation with a wide tuning range based on self-injection locking and Pound-Drever-Hall is proposed. The phase noise of generated heterodyne mm-wave by light beating of two distributed feedback lasers (DFB) is greatly suppressed when two laser lights are frequency-locked to different resonant peaks of a super stable Fabry-Pérot etalon. Frequency tuning of the mm-wave signal is achieved by simply varying the temperature of one DFB laser so that its light frequency is locked to the tracking resonant modes of the etalon. In the experiment, the generated mm-wave signal tuned from 30 GHz to 87.5 GHz with an interval of 2.5 GHz is observed to be of high flatness less than 0.5 dB. The single-sideband phase noise of the generated mm-wave is proven to be nearly irrelevant to the operating frequency and is measured to be -110 dBc/Hz @ 100 kHz, which is 10 dB lower than that of a commercial 60 GHz analog signal generator. The Allan deviation of generated 60 GHz mm-wave signal reaches 5.1×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-10</sup> within the average time of 100 s, indicating a long-term frequency stability.