以雷射注入鎖頻達成光學載波與旁波帶間之相位控制

Abstract

當一個的主要 (master)半導體雷射光源注入另一個從屬 (slave) 半導體雷射光源的共振腔中，並且使後者的中心頻率與前者的頻率相同時，即產生所謂光學注入鎖頻(Optical Injection locking)的現象。此時根據失調(detuning)程度與雷射強度，從屬雷射的狀態可能是穩定鎖定、不穩定鎖定、或者混亂的狀態。而主要-從屬雷射的相位差也與失調程度、雷射強度比、以及鎖定頻寬(locking bandwidth)有關。 另一方面，由於對光作精確的相位控制 (phase control) 一直是一個挑戰。我們提供一個方法，針對經過聲光調制器之後的 823nm 半導體雷射所產生的載波(Carrier)與旁波帶(Sideband), 利用雷射注入鎖頻的原理，對兩者之相位差做操控。我們首先利用實驗證明若主要雷射為一拍頻光束，注入後的從屬雷射也會是相同的拍頻光。接著，我們將兩者拍頻訊號混合取出相位訊號。利用此相位訊號我們就能透過主要或從屬雷射的頻率控制來改變載波與旁波帶間的光相位差，達到相位控制的目的。

The injection locking phenomenon appears when a source laser (or a “master” laser) with a appropriated injection power is injected into a free oscillating laser (slave laser), and detuned from the frequency of it. Depending on the frequency detuning and the injection power, the slave laser can be either stably, unstably locked, or become chaotic. The phase difference between master and slave laser is also related to the detuning, injection power, and locking bandwidth. On the other hand, accurate optical phase control is always a challenge. This thesis proposes an approach, using the technique of optical injection locking, regarding to the carrier and sideband of a 823nm semiconductor laser, to control the phase between them。 We first prove by experiment that a beat note injecting radiation can also induce a beat note from the slave laser with the same frequency. Then we use this method to extract the phase signal by mixing the master and slave beat signal. By observing the phase signal we can change the frequency of the master or slave laser to control the phase difference between the carrier and sideband of the injection locked radiation.