International Journal of Infrared and Millimeter Waves, Vol. 6, No. tl, 1985 A HETERODYNE RECEIVER FOR THE SUBMILLIMETER WAVELENGTH REGION BASED ON CYCLOTRON RESONANCE IN lnSb AT LOW TEMPERATURES Elliott R. Brown, Jocelyn Keene, and T. G. Phillips Downs Laboratory of Physics, 320-47 California Institute of Technology Pasadena, California 91125 Received July 19, 1985 Abstract A new heterodyne receiver has been developed for the submillim- eter wavelength region. The mixing element is liquid helium cooled bulk n-ln~b in a quantizing magnetic field. The value of the magnetic induction is such that the detector photoresponse is dominated by cyclotron-resonance absorption. Laboratory tests have yielded double-sideband receiver noise temperatures of 250 If at 492 GHz, 350 K at 625 GHz and 510 K at 812 GHz, The magnetic induction for these tests was ~2.5 KG and the mixer operating temperature was ~1,6 If. Keywords:heterodyne detection, submillimeter wave, cyclotron reso- nance, InSb. Introduction During the past decade, the topic of submillimeter wavelength astronomy has developed considerably, One of the most important tasks in this field is the detailed observation and characterization of interstellar atomic and molecular lines, The suecessful detection of these lines demands very high spectral resolution and sensitivity that is practical only with ~xcellent heterodyne receivers. This paper deals with a new heterodyne detector based on the cyclotron-resonance- assisted photoresponse in liquid helium cooled n-lnSb, The perfor- mance of a receiver incorporating this detector has been measured at both 492 GHz and 625 GHz using frequency-multiplied klystrons as local oscillators and at 81~ GHz using a far-infrared molecular laser, At 812 GHz, the 510 K double-sideband receiver noise temperature is the best performance reported near this frequency to date. Judging from separate direct-detection measurements [i], the useful 1121 0195-9271/85/1100 1121504.50/0 1985 Plenum Publishing Corporalion