Multiwavelength Laser Based On Aperiodically Poled MgO-doped Lithium Niobate

In this thesis, we investigate the second-order frequency conversion based on quasi-phase matching (QPM) technology, including optical second-harmonic generation (SHG), sum-frequency generation (SFG) and difference-frequency generation (DFG). And the analytical solutions to the coupled-mode equations of cascaded second-harmonic generation (cSHG/DFG) are derived by using simplified calculation.We describe the structure of aperiodic optical superlattice (AOS), and demonstrate the fabrication of this kind of AOS, including the domain inversion and simulated annealing (SA) methods. The detailed discussion about the second-harmonic generation with broadened flattop bandwidth in AOS is presented in this thesis, and the relatively effective nonlinear coefficient d reffis introduced, which is utilized to study the conversion efficiency of cSHG/DFG. Meanwhile, we explain the trade-off, which shows that the broadened flattop bandwidth is bigger, d reffis smaller; the broadened flattop bandwidth is smaller, d reffis bigger, between broadened flattop bandwidth and conversion efficiency. In our design of AOS, which is an aperiodically poled MgO-doped lithium niobate (MgO:APPLN), 3 n m broadened flattop bandwidth is obtained with d reffequals to 0.112.Two schemes of multiwavelength laser based on cSHG/DFG interactions in MgO:APPLN are proposed. At least four simultaneous outputs can be realized in both two schemes. In scheme I, the output wavelengths are tunable by changing the wavelengths of two input pumps. Additionally, the outputs of the proposed multiwavelength laser can be selected by tuning the operation temperature of MgO:APPLN. The output wavelengths of scheme II are also tunable by changing the input wavelength of two pumps, while the output wavelengths are selectable through changing the input powers of two pumps. The third scheme of multiwavelength laser based on cSHG/DFG interactions in MgO:APPLN and four-wave mixing (FWM) in highly nonlinear fiber (HNLF) is proposed. In this proposal, two seed lights are generated by the cSHG/DFG interactions in MgO:APPLN, and with the seed light provided by the external cavity laser (ECL), 13 outputs are obtained through FWM in the HNLF. Meanwhile, the wavelengths and wavelength spacing between these 13 outputs can be adjusted by changing the wavelengths of the pump from ECL or the input pumps of MgO:APPLN.