在本論文中，我們推導了在低增益條件下的近似增益解析解，可以縮短在模擬光參震盪器時所花費的時間。我們也介紹了脈衝式光參震盪器的運作機制，與其光腰半徑與共振腔長的設計方式。能夠產生波長532奈米雷射的途徑有很多種，我們舉了六個達成方式來分析，由分析結果，我們選擇利用串聯倍頻，光參震盪器，倍頻的方式來達成，並且用其進行相關的生醫實驗。我們利用不同波長打入待測物，待測物會因熱膨脹而產生超聲波訊號，由於不同波長有著不同的吸收率，而產生不同的超聲波訊號大小，進而分辨待測物種類。最後，生醫實驗失敗的可能原因是由於波長選用範圍太接近所造成。

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.

CHAPTER 1: INTRODUCTION
1.1 Motivation
1.2 Nonlinear frequency mixing
1.3 Quasi-phase-matching

CHAPTER 2: THEORY OF OPTICAL PARAMETRIC OSCILLATION
2.1 Coupled-wave equations
2.2 Continuous wave optical parametric oscillation
2.3 Nanosecond pulsed- optical parametric oscillation

CHAPTER 3: DESIGN OF A NONLINEAR YELLOW LASER
3.1 Analysis of a nonlinear yellow laser generation
3.2 Cavity design

CHAPTER 4: EXPERIMENTAL RESULTS
4.1 Experimental setup
4.2 Experimental results and discussions
4.3 Conclusion

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