二極體雷射頻率控制之研究

Abstract

以近紅外光雷射合成一高穩定的次毫米波連續光源，需要兩個基本元件，即一穩定之雙波長連續波雷射光源與一有效率可將近紅外雷射光轉換成次毫米波之混頻器(Photomixer)。本論文主要是研究雙波長雷射光源中所需的頻率控制方法，研究對象為850 nm二極體雷射。 論文內容包括下列三部分： 1.注入鎖定(Injection Locking) 在注入鎖定的實驗中，我們成功地以TUI光柵回授二極體雷射(線寬 約為100 kHz)，將一SDL雷射(功率為100 mW)鎖定，並探討頻率鎖定範圍與注入訊號之關係，測量結果與理論非常符合。 2.外腔式雷射系統(External Cavity Laser System) 利用一部分反射鏡與一SDL雷射120 mW之DBR雷射組成一外腔式雷射系統，採用延遲外差(Delay-Heterodyne)干涉法測量其線寬，證實可將DBR雷射之線寬從約10~15 MHz壓縮至100 kHz。 3.光學鎖相(Optical Phase Locking) 組裝一鎖相迴路，探討外腔式雷射與TUI光柵回授雷射間光學鎖相之可行性。發現雷射線寬雖然足夠小，但由於雷射結構之不穩定造成兩雷射間的拍頻有10~20 MHz的跳動，無法達成鎖相。未來將雷射之結構改進，消除拍頻之跳動，再嘗試鎖相之研究。

Use near IR laser to creative sub-mm CW light source, we need two fundamental devices, stabile dual-wavelength CW laser and photo mixer, which can efficiently convert near IR laser to sub-mm wave. This thesis focuses on the development of the frequency control method of the stabile dual-wavelength CW laser. The thesis covers the following three topics: 1.Injection Locking In the experiment, we successfully used TUI grating feedback laser (linewidth ~ 100 kHz) to lock a SDL laser, and analyze the relation of the range of the frequency locking and the inject signal, the results match the predictions of theory. 2.External Cavity Laser System Use a partial reflective mirror and a 120-mW SDL laser to set up a external cavity laser system, and try to use Delay-Heterodyne interference to measure the linewidth. We can demonstrate the linewidth of the DBR laser can be narrowed from 10~15 MHz to 100 kHz. 3.Optical Phase Locking Try to set up a phase locking loop to analyze the possibility of the optical phase locking between the external cavity laser system and the TUI feedback laser. We found the linewidth is enough narrow, but the instability of the laser structure can result in the 10~20 MHz jitter of the beat frequency, can not lock. In the future, we try to improve the laser structure to eliminate the jitter of the beat frequency, and continue the study the optical phase locking.