We report the low-threshold operation of a nanosecond β-BaB2O4 optical parametric oscillator (OPO) pumped by the third harmonic of a Q-switched Nd:YAG laser. Using cylindrical focusing of the pump beam, a threshold pulse energy of ∼0.5 mJ is obtained at the signal wavelength of 560 nm, which is about sixteen times lower than that of a spherical focusing configuration. The importance of diffraction loss in the design of tightly focused OPOs is discussed in terms of a simple extension of the conventional OPO model. © 2007 Elsevier Ltd. All rights reserved.
Bapna, R. C., Rao, C. S., & Dasgupta, K. (2008). Low-threshold operation of a 355-nm pumped nanosecond β-BaB2O4 optical parametric oscillator. Optics and Laser Technology, 40(6), 832–837. https://doi.org/10.1016/j.optlastec.2007.11.009