Coherent Signal from Incoherently cw-Pumped Singly Resonant Ti:LiNbO{sub}3 Integrated Optical Parametric Oscillator

摘要

Quasi-phase-matched, singly resonant integrated optical parametric oscillators (SR-IOPO), with feedback at the signal wavelength only, offer simplified tuning, high stability, high conversion efficiency, and a low threshold in comparison with bulk devices [1]. Usually, they are pumped by narrow linewidth sources as the spectral properties of the pump are transferred to signal and idler. However, this coherence transfer is strongly determined by the dispersion properties of the waveguide material leading to surprising phenomena. Therefore, we investigate in this contribution the coherence properties of signal and idler generated by the parametric non-degenerate three-wave interaction in a SR-IOPO. In particular, operation with a broad-bandwidth cw-pump and the resulting coherence transfer to signal and idler are studied. To get a highly coherent signal we take advantage of the convection-induced phase-locking mechanism, based on a group-velocity difference between the resonant signal and the pump and idler waves, and a good group-velocity matching of the last two [2]. However, in contrast to the previous investigation for a type II configuration [2], we show here the feasibility of coherent signal generation from an incoherent cw-pump at λ{sub}p = 1.535 μm in a type I {eee} Ti:LiNbO{sub}3 SR-IOPO. The wavelength of the resonant signal is λ{sub}s = 3.941 μm, near the infrared transparency limit. Around this wavelength triple (λ{sub}p, λ{sub}s, and λ{sub}i = 2.514 μm) the substrate dispersion yields significant group-velocity differences Δv{sub}(sp,si) = |v{sub}s - v{sub}(p,i)| between resonant signal and pump/idler, but a small Δv{sub}(pi) = |v{sub}p - v{sub}i| only. Both properties are necessary to get an efficient convection-induced phase-locking mechanism. In order to simulate the planned experiment we consider an SR-IOPO of length L = 3.2 v{sub}p τ{sub}0 = 8 cm. A periodicity of the ferroelectric domain structure Λ{sub}(QPM) = 30.24 μm is assumed yielding quasi-phase matching for the wavelength triple given above. The end face mirrors have a reflectivity R = 98% at the signal wavelength; optical propagation loss coefficients α{sub}p = α{sub}i = 0.1 dB/cm, α{sub}s = 0.26 dB/cm and a pump power P{sub}p = 1.3 W are used as simulation parameters.