2022/05/12 by Greenberg, James, Amin, Rubab, Heffernan, Brendan M. +1
#Applied Physics (physics.app-ph) #FOS: Physical sciences #Optics (physics.optics)
paper · doi:10.48550/arxiv.2205.06380
Optical generation of millimeter-waves (mm-wave) is made possible by an optical heterodyne of two diode lasers on a uni-traveling-carrier photodiode (UTC-PD). We utilized this technique to produce a mm-wave oscillator with desirable phase-noise characteristics, which were inherited from a pair of narrow-linewidth diode lasers. We present the long-term stabilization of our oscillator, achieved by referencing it to a rotational transition of gaseous nitrous oxide (N2O). Direct frequency modulation spectroscopy at 301.442 GHz (J=11) generated an error signal that disciplined the frequency difference between the diode lasers and thus, locked the millimeter-wave radiation to the molecular rotational line. The mm-wave frequency was down-converted using an electro-optic (EO) comb, and recorded by a frequency counter referenced to a Rubidium (Rb) clock. This resulted in short-term fractional frequency stability of 1.5 × 10-11/√τ and a long term-stability of 4× 10-12 at 10,000 s averaging time.