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We report a stable, Yb-fiber-laser-based, green-pumped, picosecond optical parametric oscillator (OPO) for the near-infrared based on periodically poled potassium titanyl phosphate (PPKTP) nonlinear crystal, using fan-out grating design and operating near room temperature. The OPO is continuously tunable across 726–955 nm in the signal and 1201–1998 nm in the idler, resulting in a total signal plus idler wavelength coverage of 1026 nm by grating tuning at a fixed temperature. The device generates up to 580 mW of average power in the signal at 765 nm and 300 mW in the idler at 1338 nm, with an overall extraction efficiency of up to 52% and a pump depletion >76%. The extracted signal at 765 nm and idler at 1746 nm exhibit excellent passive power stability better than 0.5% and 0.8% rms, respectively, over 1 h with good beam quality in TEM_00 mode profile. The output signal pulses have a Gaussian temporal duration of 13.2 ps, with a FWHM spectral bandwidth of 3.4 nm at 79.5 MHz repetition rate. Power scaling limitations of the OPO due to the material properties of PPKTP are studied.

We report a novel technique for the generation of mode-locked pulses from a continuous-wave (cw) optical parametric oscillator (OPO). The technique is based on the deployment of an electro-optic phase modulator (EOM) in combination with an antiresonant ring (ARR) interferometer internal to a cw OPO. The scheme is implemented in a doubly-resonant cw OPO based on MgO:sPPLT, configured in a standing-wave cavity and pumped at 532 nm by a cw laser. With careful adjustment of the cavity length, modulation frequency and modulation depth, under different conditions, we achieved stable train of 730 ps and 450 ps pulses at a repetition rate of 160 MHz and 80 MHz, respectively. At degeneracy, spectral broadening of ~38 nm and ~20 nm has been observed corresponding to pulses of 160 MHz and 80 MHz repetition rate, respectively. We have confirmed true mode-locked operation by verifying ~4 times enhancement in second-harmonic-generation power under mode-locked operation at both 160 MHz and 80 MHz, compared to that in cw operation, for a fixed average fundamental power.

We report a tunable, high-energy, single-pass, optical parametric generator (OPG) based on the new nonlinear material, cadmium silicon phosphide, CdSiP2. The OPG is pumped by a laboratory designed cavity-dumped passively mode-locked, diode-pumped, Nd:YAG oscillator, providing 25 J pulses in 20 ps at 5 Hz. The pump energy is further boosted by a flashlamp-pumped Nd:YAG amplifier to 2.5 mJ. The OPG is temperature tunable over 1263-1286 nm (23 nm) in the signal and 6153-6731 nm (578 nm) in the idler, corresponding to a total tuning range of 601 nm. Using the single-pass OPG configuration, we have generated signal energy as high as 636 J at 1283 nm, together with an idler energy of 33 J at 6234 nm, for 2.1 mJ of input pump energy. The signal pulses generated from the OPG have a Gaussian pulse duration of 24 ps and an FWHM spectral bandwidth of 10.4 nm at central wavelength of 1276 nm. The corresponding idler spectrum has an FWHM bandwidth of 140 nm centered at 6404 nm.

We report a compact, efficient, high-energy and high-repetition-rate mid-infrared picosecond optical parametric oscillator (OPO) based on a new nonlinear material CdSiP2. The OPO is synchronously pumped by a master-oscillator power-amplifier system at 1064.1 nm, providing 1-s-long macro-pulses constituting 8.6 ps micro-pulses at 450 MHz, and can be tuned over 486 nm across 6091-6577 nm, covering the technologically important wavelength range for surgical applications. Using a compact cavity (~30 cm) and a CdSiP2crystal, idler macro-pulse energy as high as 1.5 mJ has been obtained at 6275 nm, for an input energy of 30 mJ. The extracted signal pulses have durations of 10.6 ps.

We report efficient generation of picosecond pulses in the near- and mid-infrared in the new nonlinear material CdSiP2pumped at 1.064 m by an amplified mode-locked Nd:YVO4laser at 100 kHz repetition rate. Using single-pass optical parametric generation in 8-mm-long crystal cut for type I (e→00) noncritical phase-matching, an average idler power of 154 mW at 6.204 m together with 1.16 W of signal at 1.282 m has been obtained for 6.1 W of pump at photon conversion efficiencies of 15% and 23%, respectively. Signal pulse durations of 6.36 ps are measured for 9 ps pump pulses, with both signal and idler beams in near-Gaussian spatial profile.

We report a simple, compact and novel implementation for single-pass second-harmonic-generation (SP-SHG) of continuous-wave laser radiation based on a cascaded multi-crystal scheme, which can provide the highest conversion efficiency at any given fundamental power. By deploying a suitable number of identical 30-mm-long MgO:sPPLT crystals in a cascade, and a 30-W cw Yb-fiber laser at 1064 nm as the fundamental source, we demonstrate SP-SHG into the green with a conversion efficiency as high as 56% in the low as well as high-power regime, providing a 5.6 W of green output for 10 W and 13 W green output for 25.1 W of input pump power. The multi-crystal scheme permits substantial increase in cw SP-SHG efficiency compared to the conventional single-crystal scheme, without compromising performance with regard to power stability and beam quality.