Abstract

In recent years the development of green-pumped, cw singly resonant optical parametric oscillators (cw SROs) based on undoped periodically poled LiNbO₃ (PPLN) has been impeded by the effects of photorefractive damage and green-induced infrared absorption (GRIIRA) [1,2]. It has been demonstrated that both effects are eliminated or at least significantly reduced for MgO doped LiNbO₃ [3,4]. Nevertheless MgO doped stoichiometric periodically poled LiTaO₃ (MgO:sPPLT) was the preferred nonlinear material for green-pumped cw SROs in recent works [2,5,6]. We here show that it is possible to build a stable cw SRO from (5 mol%) MgO doped PPLN pumped at 532 nm by a single-mode DPSS laser. The device features a low threshold which is reduced by a factor of more than 2.3 compared to similar devices made of MgO:sPPLT. The experimental setup is depicted in Fig. 1(a). The ring cavity is resonant for the signal wave and one mirror (M3) is mounted on a piezo-actuator for scanning and controlling the cavity length. The temperature controlled, 40 mm-long MgO:PPLN crystal (grating period Λ = 7.3 μm) is placed between the mirrors Ml and M2. An uncoated glass etalon inside the resonator allows for frequency fine tuning. As shown in Fig. 1(b) parametric oscillation occurs at P_pump ≥ 1.2 W. At a pump power of 2 W we yield a maximum idler power of 310 mW at an idler wavelength of 1416 nm (conversion efficiency 41%). Single-mode signal operation is confirmed by monitoring the transmission of a scanning FPI (FSR = 1 GHz). The SRO is operated at temperatures from 40.0°C to 80.0°C giving access to an idler wavelength range of 1406-1451 nm (corresponding signal wavelength range: 840-856 nm).

© 2009 IEEE