Compact, efficient and widely tunable 2-μm high-repetition-rate optical parametric oscillators

Abstract Compact efficient high-repetition-rate tunable optical parametric oscillators (OPOs) in the 2- μ m region were investigated, based on nonlinear crystals of KTP and periodically polarized LiNbO3 (PPLN) intracavity pumped by a diode-end-pumped acousto-optical (AO) Q-switched Nd:YVO4 laser. The cavity was designed and optimized from the theoretically analysis on thermal stability and mode matching. Using walk-off compensated twin KTP-crystal pairs as the nonlinear media, the maximum output power of 4.15 W was obtained at 25 kHz and the tuning range spanned from 1923.22 nm to 2378.63 nm, pumped at the diode power of 18.41 W at 808 nm. The optical–optical conversion efficiency of 22.5% and the photon conversion efficiency of around 60% are both among the highest in intracavity pumped OPOs. To overcome the power degradation during angle tuning, a type-II quasi-phase matched (QPM) PPLN crystal with temperature tuning was also studied. With a 55-mm-long 14.1- μ m-grating period PPLN crystal, the maximum output power was 3.41 W corresponding to the optical–optical conversion efficiency of 18.5%. Both the KTP and PPLN OPOs demonstrated good efficiency as well as temporal, spectrum and beam characteristics, providing excellent 2- μ m laser source for applications of lidar, medical diagnosis, nonlinear frequency conversion to the long-wave infrared and terahertz range, etc.

[1]  K. Zhong,et al.  Enhancement of terahertz wave difference frequency generation based on a compact walk-off compensated KTP OPO , 2010 .

[2]  Liejia Qian,et al.  Over 20-W Mid-Infrared Picosecond Optical Parametric Oscillator , 2015, IEEE Photonics Journal.

[3]  Eiko Takaoka,et al.  Sellmeier and thermo-optic dispersion formulas for KTP. , 2002, Applied optics.

[4]  Konstantin L. Vodopyanov,et al.  ZnGeP 2 optical parametric oscillator with 3.8–12.4-µm tunability , 2000 .

[5]  P B Phua,et al.  Compact 21-W 2-mum intracavity optical parametric oscillator. , 2000, Optics letters.

[6]  W. Shi,et al.  High-Repetition-Rate Terahertz Generation in QPM GaAs With a Compact Efficient 2- $\mu \text{m}$ KTP OPO , 2016, IEEE Photonics Technology Letters.

[7]  R. A. Fields,et al.  Thermal modeling of continuous‐wave end‐pumped solid‐state lasers , 1990 .

[8]  Biao Wang,et al.  Compact Efficient 2.1- $\mu $ m Intracavity MgO:PPLN OPO With a VBG Output Coupler , 2015, IEEE Photonics Technology Letters.

[9]  W. Shi,et al.  High power, widely tunable dual-wavelength 2 μm laser based on intracavity KTP optical parametric oscillator , 2017 .

[10]  D. Hanna,et al.  High-power cladding-pumped Tm-doped silica fiber laser with wavelength tuning from 1860 to 2090 nm. , 2002, Optics letters.

[11]  Martin M. Fejer,et al.  Terahertz-wave generation in quasi-phase-matched GaAs , 2006 .

[12]  V. Pašiškevičius,et al.  ZnGeP2 parametric oscillator pumped by a linewidth-narrowed parametric 2 microm source. , 2006, Optics letters.

[13]  L. Becouarn,et al.  Optical parametric oscillation in quasi-phase-matched GaAs , 2004, Conference on Lasers and Electro-Optics, 2004. (CLEO)..

[14]  Mali Gong,et al.  High-slope-efficiency 2.06 μm Ho: YLF laser in-band pumped by a fiber-coupled broadband diode. , 2016, Optics letters.

[15]  W. Shi,et al.  Widely-tunable high-repetition-rate terahertz generation in GaSe with a compact dual-wavelength KTP OPO around 2 μm. , 2016, Optics express.

[16]  Xiaowen Shu,et al.  70-W average-power doubly resonant optical parametric oscillator at 2 μm with single KTP , 2014 .