Intra-cavity Frequency Doubling Of Femtosecond Optical Parametric Oscillator

Optical parametric oscillators (OPO), as efficient, tunable devices for frequencyconversion, have attracted much attention of research works. In this thesis,intra-cavity frequency doubling of synchronously-pumped optical parametricoscillator was investigated. The main research works were summarized as follows:(1) The principle and development of optical parametric oscillator wereintroduced;(2) Nonlinear optical frequency conversion and quasi-phase matching technologywere introduced;(3) Based on the theory of frequency doubling and energy conservation law, thephase matching angle and effective nonlinear coefficient of BBO crystal wereanalyzed in type Ⅰ and type Ⅱ phase matching。The results show that a wider spectralrange and a larger effective nonlinear coefficient can be obtained in type Ⅰ phasematching. So type Ⅰ phase matching is preferred to type Ⅱ phase matching for thefrequency doubling process of BBO;(4) A ring-cavity synchronously-pumped optical parametric oscillator wasinvestigated, which was pumped by a self-mode-locked Ti:sapphire laser. Aperiodically poled KTiOPO4crystal was used in the oscillator, and the parametricoperation was obtained. The wavelength of the signal wave could be tuned from1000nm to1500nm. The signal wave was successfully frequency doubled by inserting aBBO crystal in the cavity. The wavelength of second harmonic could be tuned from550nm to650nm freely by cavity-length tuning. In order to analyze the loss in thecavity and the threshold of the pump power, a thin glass substrate was inserted intothe cavity to couple the light out, then the output power was measured; furthermorethe loss and dispersion in the cavity was discussed.