缺陷共振腔高階模態研究

Abstract

本文在傳統雷射共振腔之中置入缺陷，製造出一個光波無法穿越的區域，進而造成雷射模態結構產生改變。實驗結果證實共振腔內的缺陷可以成為一個全新調整雷射模態的因素。

一維 Hermite-Gaussian (HG) 模態實驗結果證實操控金屬細線在共振腔內的位置可使HG模態轉換為落在幾何軌跡上的光束。利用該方式得到的雷射模態與透過離軸激發方式得到的結果有很好的對應。以HG模態作為基底進行數值分析，缺陷共振腔產生的模態也與HG簡併態的疊加結果有著良好的對應。

二維HG模態實驗結果亦顯示透過金屬細線形成的缺陷共振腔可操控雷射模態落在利薩如軌跡之上。更進一步發現共振腔缺陷所在的位置與相位有著密切的關係。藉由控制缺陷的位置可以有效的控制利薩如圖形的相位。

缺陷共振腔有別於以往盡可能降低腔內的干擾，以金屬細線影響雷射光在腔內的傳播，最後達到改變雷射模態結構的目的。實驗結果顯示了以金屬細線作為缺陷能有效操控雷射模態，成為一個重要的實驗參數。

In this research, we applied an additional mental wire into laser cavity served as an artificial defect to block the original light path. We’ve found this adjustment may interfere with output laser mode.

In the experiment of one-dimensional Hermite-Gaussian (HG) modes with an obstacle, the trajectory change matches the experimental results and numerical simulation of an off-axis laser perfectly.

Previous research suggests that if the ratio of L-mode and T-mode within a degenerate resonator is a rational number, than the superposition of each 2D HG modes will be localized on Lissajous parametric surfaces. However, an external obstruction may disturb the formation of Lissajous pattern. Thus, the position of the obstacle plays an important role in two-dimensional HG modes experiments, not only the Lissajous pattern matches with 2D off-axis laser, we also can control the phase of Lissajous pattern by fine tuning the opaque-wire.

Unlike traditional laser experiments, which usually try to reduce the number of defaces in laser cavity as much as possible, our newly developed technique becomes another useful method which also can manipulate laser modes.