Abstract
In the thesis, we have investigated on distributed feedback structure toward optical parametric oscillation. In order to fabricate a grating structure in the nonlinear gain medium such as MgO: LN, we used nano-second 355 nm UV pulse laser with interferometer technique to induce a periodical refractive index modulation (grating) structure, and this phenomenon is generated by photorefractive effect. Also, we demonstrated an optical parametric generation in MgO: LN which is used to detect the DFB structure. In our knowledge, Mg-doped LiNbO3 is better than pure congruent LiNbO3 with low noise, fast photorefractive response time, higher photorefractive sensitivity and optical damage threshold. We demonstrated a type I phase matching optical parametric generation with pump 532 nm by changing the temperature of the crystal from 200.7 to 106.5℃. The results shows a wide tuning range of signal and idler from 817.5 to 1523 nm. In order to design a tunable resonated cavity structure which means a tunable grating structure, we investigated on Indium Tin Oxide (ITO). In the experiment, when we pump a 355 nm UV with interferometer pattern, we discovered that there is a transient grating structure in the ITO by two-photon absorption. The maxima value of the refractive index change in ITO is ∆n=4.1×〖10〗^(-3). The tunable grating period in our interferometer setup is widely from 193.6 nm to 766.7 nm, which means the resonated wavelength is from 890nm to 2.5 μm. This particular transient grating result may give a chance on DFB OPO wave guide in future. Furthermore, in theoretical simulation, we combined the coupled-wave theory with DFB theory to discuss the longitudinal mode selectivity and parametric threshold gain, also we modified the simulation with considering the absorption term completely. At last, we used the present experimental results and then combined it into the theory. To understand the physics and the opportunity for application.