All-fiber CW fiber optical parametric oscillator tunable over 240 nm.

Abstract

Widely-tunable pulsed fiber optical parametric oscillator (OPO) sources, with sideband detunings in excess of 150 THz, have recently been demonstrated [1,2]. Continuous-wave (CW) fiber OPOs have also been realised but with a much restricted tunablity (below 100 nm around 1550 nm) [3,4]. In this paper we present a CW fiber optical parametric oscillator with a tuning range in excess of 240 nm. To our knowledge this is the largest tuning range yet demonstrated for a CW χ(3) oscillator. Key to the operation of this device is the Raman effect that can be exploited to lower the threshold of the device. The oscillator we propose is a singly resonant fiber ring. The threshold power is set at the point where the roundtrip gain of the resonant sideband is equal to its roundtrip loss. Considering the effects of both the Kerr nonlinearity and Raman scattering in a fused-silica fiber we plot in Fig. 1(a) the normalised threshold power, γ P T L (γ nonlinear interaction coefficient, P T threshold power, L fiber length), of the oscillator as a function of output sideband detuning for a resonant roundtrip feedback fraction α = 0.5 . Figure 1(a) shows that at all frequencies between 0 and 30 THz it is advantageous to operate a singly resonant fused-silica fiber OPO with the Stokes wave resonant rather than the anti-Stokes wave.