The First Radioastronomical Observation with Photonic Local Oscillator

We present the results of experimental radioastronomical observations of an interstellar molecular spectral line with an SIS (superconductor–insulator–superconductor) receiver pumped by a photonic local oscillator (LO). A millimeter-wave LO signal was generated by feeding an optical comb signal into a W-band (75–110 GHz) photomixer using a uni-traveling-carrier photodiode (UTC-PD). A CS $$J = 2 \hbox{--} 1$$ line at 98 GHz was observed toward a high-mass star-forming region W 51 ($$\mathrm{H}_2 \mathrm{O}$$). We compared the obtained spectra with those obtained with a conventional Gunn oscillator as an LO. As a result, the line parameters, such as the width, intensity, and frequency, were consistent with each other. The results presented here show that the photonic LO is a very promising source for heterodyne receivers in millimeter–and submillimeter-wave astronomy.