28-dB gain mid-infrared optical amplification using resonant quantum cascade laser optical amplifier

Abstract

We report the operation of quantum cascade lasers (QCLs) as a mid-infrared photodetector as well as a tunable resonant amplifying detector. When biased at low voltage or without bias, QCL works as a photoconductive or photovoltaic detector. When biased near threshold, QCL operates as a tunable resonant amplifying detector. The detected signal reaches its maximum when the QCL bias is close to its threshold. The maximum signal power is over 28 dB higher compared with the case without bias. These interesting mid-IR detection and amplification characteristics of QCL gain material can help with mid-IR optical filtering and photonics integration.