Tailoring the pulse characteristics of LiB₃O₅-based femtosecond optical parametric oscillators by temperature tuning

We show that the phase mismatch in LiB₃O₅ (LBO) crystals is approximately proportional to the temperature deviation from the phase-matching temperature of crystals. Moreover, a fixed temperature deviation would result in approximately the same amount of phase mismatch over a large range of wavelengths. Based on this, we demonstrate that the pulse characteristics of LBO-based femtosecond optical parametric oscillators (OPOs) can be tailored by simply tuning the crystal temperature. Experimentally, at a temperature deviation of 10°C, nearly transform-limited optical pulses were obtained over a tuning range of 780-910 nm, and at a temperature deviation of -9°C, linearly chirped pulses with broadened spectra were obtained, which were de-chirped to be nearly transform-limited ones outside the cavity. The capability of generating femtosecond pulses with different pulse characteristics and at various wavelengths would benefit many applications, including spectroscopy and Raman microscopy.