Observation of High Precision Frequency Tuning of Terahertz Quantum Cascade Lasers Employing a Laser Beating Scheme

We demonstrate a laser beating system to investigate the frequency tuning characteristics of terahertz quantum cascade lasers (QCLs) induced by temperature or drive current. The system is composed of two QCLs, one is operated as a frequency comb and the other is driven at lower current to emit a single frequency. Experimental results show that the frequency tuning coefficients of the terahertz QCL are 6.1 MHz/0.1 K (temperature tuning) and 2.7 MHz/mA (current tuning) that have not been revealed by traditional terahertz spectrometers.