| Summary: | 碩士 === 國立清華大學 === 光電工程研究所 === 102 === In this thesis, we derived the analytic solution of continuous-wave parametric gain under the low gain and depleted pump conditions. We also numerically analyzed the nanosecond pulse optical parametric oscillator (OPO), and the way how to calculate the efficiency and chose the suitable beam waist and cavity length. We used a Nd:YAG pump laser and three periodically poled lithium niobate (PPLN) crystals to implement the cascaded second-harmonic generation (SHG)-OPO-SHG processes to generate 4 kHz repetition rate, 7.5 mW yellow laser at 584 nm with 1.54% power fluctuation. The yellow laser was used in on biomedical experiment. The biomedical experiment has to measure the photoacoustic signal of the object by using three different wavelengths. When laser input an object, it creates thermal expansion and we can use the ultrasonic sensor to receive the photoacoustic signal of vibration that thermal expansion makes. The absorption of the objects determine the photoacoustic signal energy, and we can use it to separate sort of the objects. Finally, the biomedical experiment has fail because the interval of different wavelengths is too close to distinguish the different absorption.
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