Fig. 1. Schematic of high-efficiency, low threshold, high repetition rate H-β Fraunhofer line light at 486.1 nm generation by an intracavity frequency-doubled SR-OPO.

Fig. 2. Fundamental-mode beam size of the signal wave in (a) sagittal plane and (b) tangential plane.

Fig. 3. (a) Power transfer and (b) conversion efficiency of the signal output in SR-OPO at different transmittances (T = 20%, 30%, 40%).

Fig. 4. (a) Spectrum of 972.2 nm at the maximum power of 1.9 W (FWHM); (b) oscilloscope trace of 972.2 nm at 1.9 W; inset, pulse train of 972.2 nm.

Fig. 5. (a) Power transfer at 486.1 nm; inset, oscilloscope trace of 486.1 nm at the maximum power of 1.6 W; (b) spectrum of 486.1 nm at 1.6 W.

Fig. 6. (a) Beam quality measurement of the 486.1 nm output at the maximum power of 1.6 W; inset, beam profile collected; (b) power stability of the 486.1 nm output at the maximum power over 2 h.