NEP characterization and analysis method for THz imaging devices

Abstract

Over the last decade, significant progress has been made in the development of Terahertz (THz) imagers to satisfy the growing interest for see-through devices for different market applications. The noise-equivalent power (NEP) is a widely accepted figure of merit used to compare the sensitivity performance of detectors. However, with no widely recognized standard for NEP, it is often difficult to have a fair comparison between different sensors. Having a clear understanding of the characterization method used to calculate this important metric will lead to better estimation of the performances that could be expected from an imaging device. There is some confusion regarding whether NEP should be expressed in terms of power (W) or power by spectral density (W/Hz1/2). The difference between the two expressions is the normalization of the first by the square root of the detector’s equivalent noise bandwidth (ENBW). By properly defining the ENBW for a specific sensor, the translation between the two is then consistent. This paper presents the NEP characterization of INO’s Microxcam-384i camera over a wide frequency range. A description of the measurement setup is provided, as well as the details of the analysis method, including the estimation of the ENBW. Finally, values for the NEP using both expressions are provided for wavelengths between 70μm (4.5 THz) and 1.5mm (198 GHz), demonstrating the broadband sensitivity of the camera.