Fiber Optical Parametric Oscillator With Wide Tuning Range and Fixed Repetition Rate

We present a widely wavelength-tunable fiber-based optical parametric oscillator (FOPO) with a fixed repetition rate using four-wave mixing in a photonic crystal fiber and an intracavity spectral filter. The FOPO produces nearly transform-limited pulses with a spectral width of 1.1 nm and a pulse duration of 1.0 ps. By changing the wavelength of a pump laser and the passband of the spectral filter, the tuning range between 832 and 922 nm is achieved. Over the entire range, the displacement of a delay stage required to match the cavity round trip time with the period of the pump pulses is as small as 0.8 mm. The present FOPO synchronized with a low-noise picosecond laser will be useful for sensitive and broadband vibrational imaging by stimulated Raman scattering microscopy.