Tunable and narrow linewidth yellow beam generation by sum-frequency mixing of diode-pumped Nd:YAG ring lasers

Output power of 1.1 W and linewidth of 0.7 GHz and beam quality of M² = 1.2 yellow beam was generated by sum-frequency mixing 1064 nm and 1319 nm radiations of quasi-continuous-wave diode-pumped Nd:YAG lasers inside a pair of KTP crystals. The narrow linewidth 1064 nm and 1319 nm beams were realized by inserting solid etalons in the three-mirrors ring resonators. The wavelength of yellow laser was adjusted and controlled by the control of etalon angle and temperature. To achieve the high beam quality at the average power, thermally near-unstable resonators with two-rod birefringence compensation were designed and employed in the 1064 nm and 1319 nm ring lasers. The high sum-frequency efficiency was obtained by using a pair of KTP crystals with a walk-off-compensated configuration. The power of the diffraction-limited, narrow linewidth and precise-tunability yellow laser was reached to 1.1 W by mixing the 1064 nm beam of 7.5 W and the 1319 nm beam of 3.2 W.