以錐形半導體放大器為增益介質、外腔VBG回饋半導體雷射研究

Study of external cavity VBG-feedback laser using semiconductor tapered amplifier as the gain medium

詹偉平(Wei-ping Chan)

指導教授 ： 鍾德元

國立中央大學/理學院/光電科學研究所/碩士(2010年)

摘要

本論文主要說明可調式的藍紫光雷射系統及利用感光材料製做體積全像布拉格光柵(Volume Bragg Grating, VBG)的技術，首先介紹目前氬離子雷射(波長為488 nm)的應用，而在實驗上引入利用窄化藍紫光半導體雷射頻寬和用紅外光半導體雷射搭配倍頻晶體來將紅外光波長轉換至可見光波段來取代氬離子雷射的構想。
本實驗我們架設兩種半導體雷射系統架構：一種為藍紫光半導體雷射(波長為405 nm)搭配體積全像布拉格光柵(VBG)作為其線型外腔式共振腔的反射鏡；另一種則使用半導體雷射錐形放大器(Tapered amplifier) 做為光源，利用可同時修正雷射的模態且可將輸出功率放大的特性搭配體積全像布拉格光柵(作為其線型外腔式共振腔和V型外腔式共振腔反射鏡)來改善我們所使用的雷射光學品質，其中所架設V型外腔式共振腔以繞射中心波長比輸出波長還長的VBG同時作為波長選擇及橫向模態選擇器，並以一介電平面鏡做為共振腔的反射鏡，架設依改變頂角大小來選擇波長機制的可調式波長系統。
目前常見的可調式雷射系統所應用的元件，由於其元件需同時達到調變雷射波長及模態選擇，卻必須提高整體系統的損耗，故本論文使用體積全像布拉格光柵這光學元件並嘗試用感光高分子材料(PQ:PMMA)搭配Two-beam interference架設來製作此光學元件。
再來使用不同的光學儀器量測各架設下雷射的特性，藉由光譜儀及Fabry-Perot干涉儀量測可得窄頻寬的藍紫光半導體雷射(FWHM~0.13 pm)且功率約為106.2 mW輸出，而可調變紅外光雷射系統可調波長範圍大約37 nm~38 nm(FWHM~30 pm)，以PQ:PMMA製作其VBG繞射光譜頻寬約5.1 nm，其繞射效率約38.21%。

關鍵字

感光高分子材料 ； 錐形放大器 ； 體積全像布拉格光柵 ； 外腔式共振腔

並列摘要

This research explained the blue-violet light tunable laser systems and use the photographic material to make the volume holographic grating (Volume Bragg Grating, VBG) . First, current applications for argon ion laser (488 nm wavelength) were introduced. The infrared laser diode and nonlinear crystal are used together to convert infrared light to visible light for replacing argon ion laser .

In this thesis, we demonstrated two semiconductor laser systems setup: one for the blue-violet semiconductor laser (wavelength for 405 nm) using a volume holographic Bragg grating (VBG) as linear external cavity mirror；the other uses the tapered amplifier for light source. The laser can correct the mode and amplify the output power with a volume holographic grating (as linear external cavity and V-cavity external cavity mirrors) to improve the laser optics. The V-cavity external cavity uses VBG with the central wavelength longer than the output wavelength to select the wavelength and transverse mode and using the dielectric mirror as a cavity mirror. The wavelength tunable system is set up using the changes in the angle for wavelength selection.

A typical application of tunable laser systems requires modulated laser wavelength and transverse mode, but this will increase the system loss at the same time. Therefore, this thesis shows the use of light-sensitive polymer (PQ:PMMA) to make volume holographic Bragg grating with Two-beam interference.
Using different instruments to measure the laser characteristics, we observed the narrowed bandwidth of the blue-violet semiconductor laser (FWHM ~ 0.13 pm, output power~106.2 mW) with spectroscopy and Fabry-Perot interferometer. The tunable infrared laser system has a tuning range of approximately 37 nm ~ 38 nm (FWHM ~ 30 pm). PQ:PMMA is used to make the VBG of diffraction spectrum bandwidth of 5.1 nm and diffraction efficiency roughly 38.21%.

並列關鍵字

Tapered amplifier ； external cavity ； Volume Bragg grating ； PQ:PMMA

參考文獻

1. Tanaka, T., et al., Tunable blue laser compensates for thermal expansion of the medium in holographic data storage. APPLIED OPTICS, 20070901: p. 6263~6272.

2. Sugita, T., et al., 31%-efficient blue second-harmonic generation in a periodically poled MgO : LiNbO3 waveguide by frequency doubling of an AlGaAs laser diode. Optics Letters, 1999. 24(22): p. 1590-1592.

3. 余兆陞, 以鎂掺雜鈮酸鋰製作二倍頻藍光雷射波導元件之製

6. Efimov, O.M., et al., High-efficiency Bragg gratings in photothermorefractive glass. Applied Optics, 1999. 38(4): p. 619-627.

7. Venus, G.B., et al. High-brightness narrow-line laser diode source with volume Bragg-grating feedback. in High-Power Diode Laser Technology and Applications III. 2005. Bellingham, WA, USA: SPIE.