Abstract
We present a three-stage PPLN nonlinear optical process for producing sodium D1, D2 wavelengths, 589.6 nm and 589.0 nm. For the purpose of producing the 589-nm wavelength, we adopt 1064-nm pumped bow-tie ring cavity optical parametric oscillation (OPO), oscillating at its signal wavelength, 1767 nm. In order to obtain the third harmonics of the 1767 nm OPO signal, another PPLN crystal, containing a second harmonic generation (SHG) section, a sum frequency generation (SFG) section, and a dispersion compensation section, was installed in the same OPO cavity. The quasi-phase-matching periods of the OPO, SHG, and SFG PPLN sections are 30.67 □m, 23.93 □m, and 9.73 □m, respectively. The phase matching temperatures of the OPO and cascaded SHG and SFG PPLN crystals are 170.55 oC and 176.57 oC. The lengths of the OPO, SHG, and SFG sections are 5 cm, 1 cm, and 1cm, respectively. The total cavity length is 53 cm. Based upon our cavity design, the calculated mode sizes at the OPO PPLN and the cascaded SHG and SFG PPLN crystals are both ~ 80 □m. Theoretical calculation indicates that the continuous-wave oscillation threshold is 0.4 W if the power loss of the 1767-nm wave is 1 %. When the 1064-nm pumping power is 3 times above the oscillation threshold, the overall up-conversion efficiency is ~ 10 % from the 1064-nm power to the 589-nm laser power. In this dissertation, instead of continuous-wave operation, we demonstrate pulse operation by pumping the bow-tie ring cavity with a Q-switched Nd:YVO4 laser. The Nd:YVO4 laser produces laser pulses with 13-ns pulsewidth at a 6-kHz repetition rate. The pumping threshold energy is 8.53 □J and the conversion efficiency from 1064-nm to the sodium line was around 0.02 %.