雷射系統的頻率差值及共振腔橫向邊界尺寸 對大面積面射型雷射螢光光譜影響之研究

Abstract

面射型雷射的共振腔是以DBR做為前後反射鏡，主動區周圍還以氧化層將電流與光子限制在其內部。共振腔的設計使其本身可以被視為準二維結構，由氧化層的範圍決定二維邊界的形狀。面射型雷射由於被放大的自發放射(amplified spontaneous emission)以及光與共振腔的交互作用，使次臨界電流下產生的螢光能夠有相當清楚的結構。為了了解光與邊界的交互作用情形，我們分析螢光光譜中橫向波向量部分的資訊，為一數量有限的序列脈衝函數。對函數作傅立葉轉換，最後得到一特徵長度譜線。不同脈衝位置的特徵長度剛好對應到二維邊界內不同的週期軌道長度，因此面射型雷射的螢光光譜可以用在二維邊界的週期軌道之研究上。不過，光譜中的脈衝序列是以有限的形式存在，光譜的結構會影響到傅立葉轉換與週期軌道的對應情形。影響光譜結構的因素有許多種，例如共振腔的橫截面積、溫度造成頻率差值的改變、共振腔內部得電流分佈等。這本論文的主要內容就是分析這些因素是如何影響螢光光譜與週期軌道的對應情形。

In VCSEL, the laser resonator consists of two distributed Bragg reflector (DBR) mirrors parallel to the wafer surface with an active region bounded by oxide layers. Current and photons are confined in active region. The cavity can be regarded as quasi two-dimensional structure, and the transverse boundary is determined by oxide confinement. The sub-threshold luminescence can have clear structure because of the amplified spontaneous emission and the interaction between light and cavity. We measure spectrum and analysis the information of transverse part, which is a sequence impulse function with limited numbers. The Fourier-transform result of this function is a length spectrum in which the characteristic lengths correspond to different periodic orbits of 2D boundary. The morphology of spectrum can be obviously affected by operating conditions and boundary. So we want to discuss the influence factors on sub-threshold luminescence emitted from VCSELs, ex: cavity size, frequency detuning, current distribution.