The Study of Multi-Longitudinal Mode NIR Optical Parametric Oscillator and Visible laser

This thesis has basically two parts: (1) Build a degenerate pump optical parametric oscillator (OPO) with periodically poled lithium tantalate (PPLT) and two mirrors, and (2) using the source generated by OPO, we generate a series of signal in visible wavelength.
First, in the degenerate pump OPO part, we have built a degenerate pump OPO with threshold about 54 mW and slope efficiency about 47%. We also observed comb shape signal in wavelength. And the span of com shape is about 1.5nm in wavelength domain and about 14 wavenumber (cm-1) or 450 GHz in frequency domain. We have generated a series of com shape signal in our IR spectrum by our OPO.
Finally, we use comb shape IR as our next pumping source. We use two different PPLN as our experimental sample. For sample A, two different pumping source (the spectrum is different) but the result is very close, only a huge peak near 532 nm. For sample B, two different pumping source and result in two different spectrums in visible domain. The reason why two results are very different is that the range of the Quasi Phase Match period is different for each sample. We also observed comb shape signal in visible laser domain. And the span is also about 14 wavenumber (cm-1), this is because the comb shape signal in IR not only go SHG process but SFG process. Since the comb signal exist in both IR and visible domain, we can assign each other and to find the nonlinear process mechanism in the future.