Synchronous upconversion of quantum cascade lasers in AgGaS₂

We investigate synchronous upconversion of a pulsed, tunable quantum cascade laser (QCL) in the important 5.4-10.2 µm range, with a 30 kHz, Q-switched, 1064 nm laser. The possibility to accurately control the repetition rate and pulse duration of the QCL results in a good temporal overlap with the Q-switched laser, leading to an upconversion quantum efficiency of 16% in a 10 mm-long AgGaS₂ crystal. We investigate the noise properties of the upconversion process in terms of pulse-to-pulse energy stability and timing jitter. For QCL pulses in the 30-70 ns range the upconverted pulse-to-pulse stability is approximately 1.75%. The demonstrated combination of broad tunability and high signal to noise in the system is well-suited for mid-IR spectral analysis of highly absorbing samples.