Infrared and terahertz signal detection in a quantum Dot nanostructure

•All optical method is proposed for infrared and terahertz signal detection.•A quantum dot with appropriate energy is obtained by external voltage.•A probe and a control field interact by quantum dot for coherent population trapping.•An IR or TH signal influences the electron population in dark and bright levels.•Absorption and transmission spectra of probe field in the medium can be altered.

In this paper an all-optical method for infrared (IR) and terahertz (TH) signals detection in quantum dot nanostructure is proposed. In our model, incoming IR or TH signals do not directly excite electrons and thus thermionic dark current cancels out. Core of detector is made of four-level quantum dot nanostructure which is designed numerically by the Schrödinger and Poisson's equations. By size control of quantum dot and external voltage, one can design a four level quantum dot with appropriate energy levels which can be suitable for IR or TH signals detections. In this case, a probe and a control field simultaneously interact by four-level quantum dot for creation of coherent population trapping. An IR or TH signal can influence the electron population in dark and bright levels, therefore absorption and transmission spectrum of probe field in the medium can be altered. Thus, one can by studying of probe absorption, easily guesstimate the existence of IR or TH signals in the medium.