Intracavity frequency doubling of PPKTP-based optical parametric oscillator

A ring-cavity synchronously-pumped optical parametric oscillator was investigated, which was pumped by a self-mode-locked Ti:sapphire laser. A periodically poled KTiOPO₄ crystal was used in the oscillator, and the parametric operation was obtained. The wavelength of the signal wave covered from 1000 nm to 1500 nm. The signal wave was successfully frequency doubled by inserting a nonlinear BBO crystal in the cavity. The wavelength of second harmonic could be tuned from 550 nm to 650 nm freely by cavity-length tuning. The loss of the cavity and the threshold of the pump power, a thin glass substrate is inserted into the cavity to couple output the light, then the output power is measured for varying pump power, based on the measurement the loss in the cavity was discussed. Furthermore, the characteristic of output pulses is also measured.