二極體激發式固態雷射之基模與高階橫模之研究

Abstract

利用半導體雷射端面激發固態晶體的雷射技術研究輸出效率與激發模及腔模重疊程度的關係，並藉由數值分析得到最佳化的設計；在空間相關之速率方程式中考慮能量上轉換(ETU, Energy transfer upconversion)所造成的影響，因而設計出一結構緊密的腔體達到高效率的固態雷射。另外亦利用此種端面積發的固態雷射技術研究雷射橫模在空間上及時間上的動態特性以及大尺度的橫模變化；藉由一激發光源成一環形激發固態晶體並藉由改變輸出鏡的曲率來調整腔模的尺度。在空間橫模的變化上可以觀察到LG0,l模態，橢圓模態，雙曲線模態，以及晶格狀排列的模態。而同一頻率的模態間的交互作用輔以固態雷射固有的震盪頻率(relaxation oscillation)，使得其在時間的變化上是十分豐富的；計有調變(modulation)、混沌(chaos)、鎖定(locking)、及自發脈衝(self-pulsing)。

One issue of this dissertation is to study the influence of pump-to-mode overlap in the slope efficiency and output beam quality in diode end-pumped solid-state lasers. The space-dependent rate equations were employed to analyze the thermal effects in CW and Q-switched end-pumped solid-state lasers. Including the thermal effects into the cavity design, a 30W of TEM00 CW mode output power with good beam quality and near 1 mJ pulse energy in Q switched operation were developed. The other issue of this dissertation is to study the formation of high-order transverse modes in a microchip laser. Experimentally, a technology based on a doughnut pump profile was developed to generate pure Laguerre-Gaussian (LG) TEM*0,l modes. In addition, the dynamics of a solid-state laser sustaining the oscillation of the Laguerre-Gaussian TEM*0,l mode is investigated theoretically and experimentally. On the other hand, a new type of laser transverse modes was demonstrated in an isotropic microchip laser with a doughnut pump profile. The observed transverse modes include elliptic and hyperbolic wave patterns that are analogous to the quantum states of classical trajectories of a 2D harmonic oscillator. Finally, it was found that the transverse pattern of optical vortex lattices could be generated by controlling the transverse mode spacing, the mode size and pump profile.