以週期性極性反轉鈮酸鋰之電光效應為布拉格調變器

Electro-optic PPLN Bragg Modulator

張癸五(Guey-Wu Chang)

指導教授 ： 黃衍介

國立清華大學/電機資訊學院/光電科技產業研發碩士專班/碩士(2007年)

摘要

在此論文中，我們成功的展示一個新式且極具影響性的以週期性極性反轉鈮酸鋰之電光效應為布拉格調變器串接可調式準相位匹配非線性轉換晶體於單一晶片上。在實驗過程中，我們首先架設一個以前述布拉格調變器作為Ｑ參數調變器之主動式Ｑ參數調變雷射。此雷射以波長808 奈米之二極體雷射作泵浦源激發摻釹石榴石晶體產生波長1064 奈米之雷射。此實驗中所使用之電光效應布拉格調變器尺寸為17釐米 (長) x10釐米 (寬) x0.78釐米 (厚)，週期20.1毫米，相對應半波電壓為160伏特。此主動式Ｑ參數調變雷射再19.35瓦之泵浦公率下產生之最大輸出脈衝能量為198.7毫焦，其重複率為１千赫茲。此布拉格調變器的損耗調變在由室溫至攝氏180度之間最多有2.4%的誤差。根據前述特徵，一個非線性轉換串接此布拉格調變器得以實現。我們將前述主動式Ｑ參數調變產生之波長1064奈米之雷射重新送回此串接式晶體中之非線性波長轉換區進行非線性轉換。藉由調動相位匹配溫度，在光參數產生區中，我們成功的產生了波長由1797至2608奈米之可調式波長雷射，溫度調動範圍由攝氏100度至168度。此光參數產生區之尺寸為30釐米 (長) x7釐米 (寬) x0.78釐米 (厚)，週期31毫米。其輸出脈衝能量約為30毫焦，轉換效率在溫度調動過程中均能維持在17%。二次協頻產生則是三階二次協頻，週期19.5毫米，尺寸為30釐米 (長) x5釐米 (寬) x0.78釐米 (厚)之區段中產生。在鋒值泵浦功率6千瓦的情況下能產生%轉換效率30%之波長532奈米之綠光，其最大輸出平均功率因為光折變損傷效應而被箝制在18毫瓦。

關鍵字

週期性極性反轉鈮酸鋰 ； 布拉格調變器 ； 電光效應 ； 雷射

並列摘要

A novel, compact and monolithic Electro-Optic periodically poled lithium niobate (PPLN) Bragg modulator with tunable quasi-phase-matching PPLN has been successfully demonstrated in this thesis. In the experiments, an active Q-switched 1064nm laser pumped by 808 nm diode laser with a-cut 0.25% doped Nd:YVO4 crystal has been constructed with an EO Bragg modulator firstly. The dimension of the EO Bragg modulator is 17mm (L) x10mm (W) x0.78mm (d) with grating period Λ=20.1μm and the corresponding half-wave voltage is 160V. The maximum output energy of the AQS laser reaches 198.7 μJ under 19.35-W pump power at 1 kHz repetition rate. The loss modulation of the EO Bragg modulator is temperature insensitive by 2.4% loss deviation from room temperature to 180℃. According to this feature, a cascaded OPG/SHG nonlinear conversion section with EO Bragg modulator has an opportunity to actualize. We used the AQS 1064 nm laser generated by EO Bragg modulator and injected into the nonlinear conversion QPM sections to proceed the OPG/SHG process. A tunable wavelength laser from 1797 to 2608 nm was generated by tuning the phase-matching temperature from the 100℃ to 168℃. The dimension of OPG section is 30mm (L) x7mm (W) x0.78mm with grating period Λ=31μm. The output signal pulse energy was approximately 30 μJ and the conversion efficiency was held at 17% under different phase matching temperature. The SHG process was executed on the same chip with the 30 mm (L) x5 mm (W) x0.78 mm and grating period was Λ=19.5μm for 3rd order SHG process. The maximum conversion efficiency was 30% under 6kW peak pump power. Due to the photorefractive damage, the maximum 532nm average power was clamped at 18 mW.

並列關鍵字

PPLN ； Bragg Modulator ； Electro-optic ； Laser