Towards passive terahertz imaging using a semiconductor quantum dot sensor

Passive terahertz imaging of high spectral sensitivity can be performed using a low temperature sensor coupled to an optical system delivering radiation from room temperature. We study this system in application to security screening and material analysis. Different types of low temperature sensors based on GaAs/AlGaAs quantum dots have been designed and characterised. The most sensitive sensor, which is able to detect individual terahertz photons, consists of a quantum dot coupled to a metallic single electron transistor. This sensor requires state of the art nanofabrication. A more robust but less sensitive sensor with relaxed nanofabrication demands, the point contact, is also being developed. The spectral sensitivity of the system is determined by the excitation spectrum of the quantum dot and spectral characteristics of the antenna. We designed a sensor to make an assessment of the combination of traditional log-periodic and near field antennae coupled to the quantum dot, and to compare performance of the sensors with single electron transistor and point contact.