A Femtosecond Optical Parametric Oscillator Based on A Temperature‐Chirped Crystal

ABSTRACT We demonstrate a femtosecond optical parametric oscillator (OPO) based on using a temperature‐chirped LBO crystal as the parametric gain medium. The temperature‐chirp along the long LBO crystal is obtained by separately heating several points along the crystal. We achieve a wavelength‐tuning range over 660–945 nm for the signal wave by simply scanning the OPO cavity length, without the need to re‐align the OPO cavity. The tuning speed is only limited by the rate of scanning the cavity length. Experimentally, we have achieved a wavelength tuning speed of 124 nm ms −1 , which, to the best of our knowledge, represents the highest tuning speed that has been demonstrated for green‐pumped femtosecond OPOs. Moreover, by altering the temperature profile along the crystal, the OPO can generate chirp‐free pulses or chirped pulses over the wavelength‐tuning range. Our work provides a scheme to break the tuning‐speed limitation of conventional femtosecond OPOs based on temperature‐tuned crystals, which will benefit many applications, including biological imaging and Raman microscopy.