High-energy Picosecond-pulsed MIR lasers

Tunable sources of short laser pulses in the mid-infrared (MIR) are useful for a number of spectroscopic and materials processing applications due to the presence of characteristic vibrational absorptions of organic materials in this spectral region. Optical parametric processes offer an effective route to frequency down-conversion of readily available near-IR sources to longer MIR wavelengths. Techniques such as optical parametric generator (OPG), optical parametric amplifier (OPA) and optical parametric oscillator (OPO) have been widely employed to access the MIR spectral region, among which OPG provides simplicity and compactness, while OPA offers higher degree of control on the spectral and spatial characteristics. Despite this, OPO has unique advantages of wide tunability, high conversion-efficiency and good beam-quality, which enables widely deployment in various of applications. However, temporal synchronization between the pump and the resonated signal is required for OPO when used to produce ultrashort pulses. Hence, a long cavity length is required when pumped with high-energy pulses at a low repetition rate, which would normally impose great physical and practical issues. In this talk, I will introduce fibre-feedback OPO technology to overcome the challenge and demonstrate the development of µJ-level pulse-energy picosecond-pulsed OPO operating at low repetition-rate of 1 MHz.