We report an orientation-patterned gallium arsenide (OP-GaAs) optical parametric oscillator (OPO) offering a high degree of temporal flexibility with controllable pulse repetition rates from 100 MHz to 1 GHz and pulse durations from ∼95 ps to ∼1.1 ns. The maximum average power of 9.2-W signal (3.3 μm) and 4.5-W idler (4.9 μm) was obtained at a repetition rate of 100 MHz and a pulse duration of ∼95 ps, with a pump power of 34.3 W and at a slope efficiency of 45.4%. The corresponding total average output power of 13.7 W is the highest power achieved to date from an OP-GaAs OPO, to the best of our knowledge.

We report a high-power single-mode mid-infrared (MIR) pulse delivery system via anti-resonant hollow-core fiber (HCF) with a record delivery distance of 108 m. Near-diffraction-limited MIR light was transmitted by HCFs at wavelengths of 3.12–3.58 µm using a tunable optical parametric oscillator (OPO) as the light source. The HCFs were purged beforehand with argon in order to remove or reduce loss due to parasitic gas absorption (HCl, CO2, etc.). The minimum fiber loss values were 0.05 and 0.24 dB/m at 3.4–3.6 µm and 4.5–4.6 µm, respectively, with the 4.5–4.6 µm loss figure representing, to the best of our knowledge, a new low loss record for a HCF in this spectral region. At a coupling efficiency of ∼70%, average powers of 592 mW and 133 mW were delivered through 5 m and 108 m of HCF, respectively. Assuming the 120-ps duration of the MIR pulses remained constant over the low-dispersion HCF (theoretical maximum: 0.4 ps/nm/km), the corresponding calculated peak powers were 4.9 kW and 1.1 kW.

A compact, mid-infrared (MIR), synchronously pumped, fiber-feedback optical parametric oscillator (OPO) based on periodically poled lithium niobate (PPLN) is developed with tunable signal and idler wavelength ranges of 1472.0–1758.2 nm and 2559.1–3562.7 nm, respectively. A solid-core SMF-28 fiber and a hollow-core fiber (HCF) were used as the feedback fibers in order to compare the effect of their substantially different levels of nonlinearity. The OPO generates 1-MHz, 120-ps, MIR pulses with up to 1.50-µJ pulse energy and 11.7-kW peak power.

We report a high-energy, picosecond, mid-infrared (MIR) optical parametric oscillator (OPO), in which a length of hollow-core-fiber (HCF) is employed to enable operation at 1-MHz repetition rate in a compact cavity format. The OPO is synchronously pumped by an ytterbium-doped-fiber (YDF) master-oscillator-power-amplifier (MOPA) system, seeded by a 1040-nm gain-switched laser diode (GSLD). Using periodically poled lithium niobate (PPLN) as the nonlinear crystal, the OPO generates signal and idler beams with tunable wavelengths in the range of 1329–1641 nm and 2841–4790 nm, respectively. The OPO provides 137-ps pulses with a maximum signal energy of 10.05 µJ at 1600 nm and a maximum idler energy of 5.13 µJ at 2967 nm. This, to the best of our knowledge, represents the highest energy MIR pulses, as well as the highest total converted pulse energy (15.18 µJ), ever achieved from a fiber laser pumped picosecond OPO.

Short-pulsed mid-infrared (MIR) lasers have many important applications including spectroscopy, material processing and free space communication, where pulse parameters such as a high repetition rate and high peak power can play a critical role in enhancing features e.g. processing speed and signal-to-noise ratio [1]. Optical parametric oscillators (OPOs) are commonly used as MIR laser sources but they require temporal synchronisation between the pump and signal when used to produce short pulses [2]. Hence, picosecond (ps) OPO systems normally operate with a short cavity length for high repetition rate pulses with low peak power, or with a relatively long cavity length for pulses at low repetition rate and high peak power. Here we report a compact short-cavitylength ps OPO that can still provide high-peak-power pulses through burst-mode operation. MIR pulses at a high repetition rate of 1.5 GHz and controllable peak powers up to a maximum of 1.2 kW are demonstrated. The pump source for the OPO is a 1040-nm gain-switched laser-diode (GSLD) seeded Ytterbium fibre Master Oscillator Power Amplifier (MOPA) system, similar to the MOPA described in reference [3]. The GSLD technique offers highly controllable pulses at a choice of repetition rates and with flexible pulse duration. In this work, a pulse width of 37 ps and repetition rate of 1.5 GHz are selected for the experiment. In the MOPA, an electro-optic modulator (EOM) is employed as a time gate to suppress a variable number of pulses every 1 µs to enable burstmode operation with a 1-MHz burst repetition rate (Fig. 1a). The MOPA generates 14-W of maximum average output power for all numbers of pulses-per-burst. The OPO is of a signal-resonant linear cavity design consisting of two concave mirrors with a 40-mm-long periodically poled lithium niobate (PPLN) nonlinear gain medium. Both mirrors are of high reflectivity at a wavelength of 1.5 µm (signal) and ~81% transmission at both 1 µm (pump) and 3 µm (idler). The cavity length was set at just 15 cm to allow synchronous pumping every two signal roundtrips at a 1.5 GHz repetition rate. The PPLN crystal, having 5 channels of grating periods ranging from 29.52-31.59 µm , is mounted in an oven that allows temperature tuning from 20 to 200 °C, from which an idler wavelength tunability of 2260-3573 nm was realized (Fig. 1b). Time (ns) 900 ns Window Voltage