Multi-element receiver with semimetal film sensing element for the submillimeter thermal imagers of viewing type

Abstract

Prospects of developing multi-element receivers for the submillimeter range (SMM) on the basis of thin-film semimetallic sensitive bolometers are considered. Electromagnetic waves of the SMM band have a high penetrating power and allow developing a thermal imager for the detection and observation of objects through various materials: fabrics, cardboard, wood, etc. The previously obtained research results are summarized. On the basis of the theoretical and experimental studies and of a review of scientific, technical and patent literature, in this work, a thermoresistive converter based on single-crystal films of materials in the metal – narrow-bandgap semiconductor – dielectric transition state is selected as a sensitive element. To determine the possibilities of using thinfilm Bi and Bi–Sb system as an absorber of terahertz radiation, as well as a polyimide film as an absorption-enhancing antireflection coating, the transmission spectra and reflection spectra of single-crystal Bi films grown on a 12 μm thick polyimide substrate were measured. The measurements were performed on a setup using selective radiation reception at cyclotron resonance absorption in InSb, which records the thermal radiation of material samples in the range from 1 to 5 THz with a spectral resolution of 0.6 THz. The design and characteristics of the model receiver are presented. The experimental setup was performed using a terahertz gas-discharge laser. The NEP of the proposed receiver is ~(4 ÷ 6)∙10–11 W/Hz1/2.

Keywords

• terahertz radiation
• bolometric receiver
• semimetal films
• water vapor laser