A distributed-absorber cold-electron bolometer single pixel at 95 GHz

Abstract

We describe a Frequency Selective Surface (FSS) based distributed-absorber Cold-Electron Bolometer (CEB) pixel at 95 GHz integrated in a multi-moded horn. The FSS provides a resonant interaction with incident mm and sub-mm radiation and defines the bandwidth of the array while the horn provides the matching of the beam to the telescope optics. CEB detectors with matched impedance are integrated within the periodic elements of the FSS and generate a voltage response proportional to the incident optical power in the bandwidth of the FSS. A prototype pixel was designed, fabricated, and characterized at a temperature of 280 mK. We present optical response to blackbody radiation and fit it to the CEB model. For an absorbed power of 50 pW, we estimate an optical responsivity of 1.2 × 108 V/W and a readout dominated Noise Equivalent Power (NEP) of 1.8 × 10−15 W Hz−1/2. A measured bandwidth of 9 GHz of this detector array confirms the frequency selective nature. This prototype represents a possible solution as a detector for the 95 GHz channel of the SWIPE instrument on the LSPE balloon-borne telescope. This kind of FSS based mm-wave architecture can be easily scaled to other frequency ranges and used on any other balloon-borne telescope focal planes.