單與雙波長外腔式寬面積半導體雷射之穩頻研究

Abstract

本論文主要是針對一新型外腔可調雙波長輸出之半導體雷射的輸 出線寬及穩頻特性進行研究。 此雷射之外腔結構包括一削角入射光柵、透鏡、與條型鏡；若採 用 v 型條型鏡，可以雙波長輸出。 我們所採取的穩頻方式是以對外腔腔長作回授控制而達穩頻之目 的。方 法是以Fabry-Perot干涉儀作為系統之頻率鑑別器，經由一自製鎖 相放 大器取出誤差信號，再利用比例-積分控制迴路觸發高壓放大器， 用 此高壓信號驅動一壓電材料藉此控制腔長。 目前在實驗上我們已能將外腔式單波長可調系統自頻率漂移量約 35MHz 穩至0.892MHz，σ=1.22×10-9 at τ=1 sec.；而外腔式雙波長 可調 系統則可將每個雷射頻率的原漂移量43 MHz降至4.2 MHz，σ =1.14×10-8 at τ=2 sec.；這是雙波長雷射系統穩頻的首度報導。 The primary focus of this thesis is the investigation of the output linewidth and the feasibility of the frequency stabilization of a tunable broad- area laser diode in an external cavity . The external cavity consists of a grazing- incidence grating , lens , and strip-mirror . By using a V-shape strip mirror , the laser could be operated in a dual- wavelength mode . Frequency stabilization of the laser output is achieved by feedback control of the external cavity length . A Fabry-Perot interferometer was utilized as the frequency discriminator . The laser linewidths are lessthen 94 MHz (instrument-limited) for both single- wavelength and dual-wavelength operation . With the servo loop operating , the peak- to-peak frequency fluctuation of the tunable single wavelength external cavity laser system can be reduced from 35 MHz down to 0.9 MHz over a period of 4600 sec. . This correspond to an Allan variance of {符號 115 \f "Symbol" \s 14|} =1.22{符號 180 \f "Symbol" \s 14|}10-9 for an integrating time-constant of {符號 116 \f "Symbol" \s 14|} =1sec . For the dual-wavelength operation , the peak-to-peak frequency fluctuation decreased from 43 MHz to 4.2 MHz , or {符號 115 \f "Symbol" \s 14|} =1.14{符號 180 \f "Symbol" \s 14|}10-8 at {符號 116 \f "Symbol" \s 14|} =2 sec. To our knowledge , frequency stability of the dual-wavelength laser diode in an external cavity has been demonstrate for the first time in this work .