Abstract
In this dissertation, we study and measure the nonlinear optical coefficients of various nonlinear optical materials. The property and feasibility of these materials used in optical parametric process are discussed. These researches have been contributed to the optical parametric generation/amplification technique to obtain a narrow-band and high peak power laser for spectroscopy.To investigate nonlinear coefficients of optical materials, we first use a Q-switched Nd3+： YAG laser of optical wavelength 1064nm and peak power 4kWatt to generate powder SHG signal of several organic nonlinear optical materials including Urea, DAST, MHB, and MBST, and inorganic nonlinear optical material LiNbO3. With the known characteristics of LiNbO3, we can conclude the high nonlinear optical coefficients of these probed samples. The powder SHG efficiency from high to low is found to be as LiNbO3, MBST, MHB, and Urea. As for DAST, due to its strong absorption at the SHG signal, it mere generates fluorescent light of optical wavelength at 700nm with a line width of 100nm.Next a Q-switched Nd3+： YAG laser of higher peak power 11kWatt is used for driving the optical parametric generation(OPG) and optical parametric amplifier(OPA) processes. In OPG experiment, by varying the operation temperatures from 35oC to 165oC in 10oC increments, we scan the OPG spectra with a monolithic PPLN having eight different grating periods from 28μm to 31μm in 0.5μm increments. In OPA experiment, a 1561nm laser diode is used as the seeding source to be amplified with a 30μm-grating-period PPLN at the phase matching temperature 70 oC. In order to narrow down the 1561nm laser diode linewidth, we use optical grating to disperse it down to 4 . Since OPA laser is characterized in high peak power and narrow-band linewidth, it is very helpful for achieving high-resolution and low-detection-limit photoacoustic spectroscopy.Finally we investigate the photoacoustic spectroscopy for low concentration NH3 with CO2 laser, a detection limit of sub-ppm has been achieved. This method can certainly be contributed to environment sensing.