| 摘要: | 體積小高功率的半導體雷射泵浦固態雷射在雷射測距、顯示科技、遠端感應、光儲存、生醫以及海底通訊等方面有許多令人感興趣的應用。而Q調制雷射技術提供一種能重複地生產高能鐳射脈搏的有效方法並且能大大提升雷射的峰值功率，因此對能產生輸出功率大於瓦特等級的微型化固態雷射而言，Q調制雷射已經變成一種重要技術。 另外藉由整合雷射共振腔內元件除了可以減少共振腔對雷射的損耗以及簡化雷射光路的校準，也同時可以達到縮減雷射系統體積的優點。在傳統的雷射系統中，雷射增益物質與其他共振腔內元件(例如Q開關、偏振片、非線性晶體等)是獨立分開的，也因此內建式Q調制雷射與內建式二倍頻雷射在追求系統微小化的過程中提供其他更好的選擇。在本篇論文中，我們率先嘗試在Nd:MgO:LiNbO3晶體上整合一塊週期性極化反轉鈮酸鋰晶體(PPLN)來作為電光(EO)式Q開關並加以完成輻射波長為1.085µm的小型半導體雷射泵浦固態雷射。我們成功製作一個Nd:MgO:PPLN並同時整合雷射增益與Q調製的功能。我們的論文中顯示了半導體雷射泵浦內建式Q調制Nd:MgO:PPLN雷射的功能與光學特型藉由一塊長度為12mm、週期為13.6µm的Nd:MgO:PPLN晶體來作為雷射Q開關。當我們對Nd:MgO:PPLN晶體以5kHz的頻率以及施加260V的電壓以及吸收功率為0.61W時來做Q調制時，我們測量到雷射平均功率為7.6mW以及脈衝寬度約30ns，經計算後得知脈衝峰值功率為55W而脈衝能量為1.6µm。本文中已經完成Q調制雷射的製作，以此為基礎加以延伸，再配合PPLN來做波長轉換，相信可以成功的製作出內建式腔內波長轉換元件。Compact and powerful diode laser-pumped solid-state lasers are of particular interest for many applications, such as laser ranging, display, remote sensing, optical storage, biomedicine, and undersea communication. Laser Q-switching technique has provided an efficient way of producing repetitively high-energy laser pulses to greatly enhance the peak power of the laser and therefore become an important technique in especially a miniature solid-state laser for producing an output power >watt level. In addition to the merit of system size reduction, monolithic integration of laser intracavity elements has the obvious advantage of reducing the difficulty with resonator loss and laser alignment. While conventional laser systems have laser gain media operated separately to other intracavity elements (e.g., the Q-switches, polarizers, nonlinear crystals, etc.), self-(internal-)Q-switching and self-frequency-doubling lasers have given good alternatives of further system miniaturization. In this work, we demonstrated the first attempt of integrating an electro-optic (EO) PPLN Q-switch in a Nd:MgO:LiNbO3 crystal to realize a compact diode-pumped internally Q-switched solid-state laser radiating at 1.085μm. We have successfully integrated a 12-mm long, 13.6-μm period EO Nd:MgO:PPLN in a 17-mm long Nd:MgO:LiNbO3 laser gain medium. When the EO Nd:MgO:PPLN Q-switch was driven by a 5 kHz, 260-V voltage pulse train with a 300 ns pulse width, at 0.61-W absorbed pump power, we measured ~7.7 mW average power or 55 W peak power with 1.6-μJ pulse energy in ~30-ns laser pulse width. Since PPLN is characterized by its flexibility of structure tailoring for phase-matching an arbitrary nonlinear wavelength conversion process, the extension of currently developed internally Q-switched Nd:MgO:PPLN laser to a monolithic all PPLN internally Q-switched intracavity wavelength converter is promising. |
