Frequency-Comb-Assisted Terahertz Quantum Cascade Laser Spectroscopy

Abstract

The spectral purity of quantum cascade lasers (QCL) suggests their use in high-precision metrology applications at terahertz wavelengths. By combining a QCL with a THz frequency comb, scientists have been able to measure the frequency of a rotational transition of a gas (methanol) with a record-breaking precision of four parts in one billion.