Optical spatial filtering readout techniques for IR/THz imaging and their performance analysis

Abstract

Abstract Optical spatial filtering readout techniques (OSFRTs), such as knife-edge filtering and circular hole filtering, are broadly used in optomechanical microcantilever focal plane arrays for infrared (IR)/terahertz (THz) imaging. In order to further improve the responsivity of IR/THz imaging, it is important to improve the optical readout responsivity (ORR). However, the shape and location of the optical spatial filter cannot be well optimized for lack of a unified theoretical ORR model of OSFRTs. This paper gives and experimentally validates a unified ORR model of OSFRTs. Based on this model, the influence of the shape and location of the four commonly used spatial filters on the imaging resolution and light utilization efficiency is discussed. Both theory and experiment show that the slit filter has higher optical readout responsivity than the knife-edge filter and better light utilization efficiency than the rectangular or circular hole filters. Therefore, the slit filter should be the best of the four commonly used filters.