| Summary: | 碩士 === 淡江大學 === 物理學系 === 88 === The major purpose of this thesis is to investigate how to utilize nonlinear optical effects to generate tunable deep UV light effectively, study the influence of noncollinear phase matching upon phase matching angle, and explore the problem of asymmetrically distributed sum-frequency signal versus phase mismatch angle in BBO. Theoretically, the basic principles of sum-frequency generation (SFG) in nonlinear optical crystals were reviewed, and the situation of noncollinear phase matching was also discussed. Experimentally, the third, fourth, and fifth harmonics of an Nd:YAG laser light were made to sum-frequency in BBO or LBO with the infrared or visible output of an optical parametric oscillator system, respectively. Deep UV light beams of wavelengths from 188.7 to 269.2 nm were generated. It was found that in the short wavelength range (< 205 nm) the SFG phase matching angle of BBO is bigger than the corresponding theoretical value; this agrees with Kato’s experimental results. Also, it is noted that when the input beams are not at normal incidence noncollinear phase matching may occur, leading to a larger phase matching angle. In addition, we observed that when the SFG wavelength gets close to the absorption edge of BBO, heating effects in the crystal may be significant enough to change the phase matching angle, and this may cause an asymmetry in the SFG signal versus phase mismatch angle relation. In contrast, when using the LBO crystals the SFG wavelengths are far above the absorption edge and the relationship between SFG signal and phase mismatch angle shows good symmetry. However, both the noncollinear phase matching and heating effects on the phase matching angle were found to be insignificant in our experiment; the discrepancy between the experimentally determined phase matching angles and the theoretical values may be attributed to the inaccuracy in the Sellmeier’s equation in the short wavelength range.
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