中紅外線面射型光子晶體雷射

Abstract

中紅外線此頻段有極具發展性的光學應用，因許多氣體分子的吸收頻譜恰好在這頻段，所以我們將中紅外線InGaAsSb/AlGaAsSb雙層量子井雷射結合光子晶體結構，以光激發形式操作，形成一階布拉格繞射垂直面射出光，雷射的發光波長約在2.3μm。

此研究的架構分為單波長與雙波長，光子晶體面射型單波長雷射的空氣柱是正方週期，我們製作出三種形狀的空氣柱，有圓形、正方形、等腰直角三角形空氣柱，其中因本身結構，圓形空氣柱會有最低的threshold power與輸出能量，等腰直角三角形空氣柱會有最高的threshold power與輸出能量，此實驗還調變了Filling factor(空氣填充率)與蝕刻深度，目的在於獲得更低的threshold power，並探討輸出特性，例如L-L曲線、極性、threshold power、波長隨溫度移動率、特徵溫度的變化趨勢與其相關性。

雙波長的部分是利用正方形空氣柱在光子晶體的兩個垂直方向上，製作兩種不同週期的共振腔，因此可從實驗得到其極化pattern為兩垂直線性極化組成的。但受限於本身的threshold power，兩種波長的輸出能量，可能沒辦法在任何輸入下都保持相同的大小，不過這個構想目前只有本實驗室在中紅外波段上達成。

Mid-infrared Surface-emitting photonic-crystal distributed-feedback lasers emitting at around 2.3m are reported in this thesis. The surface emission was obtained by using second order two-dimensional photonic crystal, formed by etched air holes in the semiconductor. The lasers were operated by optical pumping. Single mode operation at and above room temperature was achieved. Three different kinds of air hole shapes were used for the photonic crystal fabrication. The dependence of device performance on the air holes’ period geometry, etched depth and the filling factor were studied. Besides single wavelength lasers, we have also fabricated two-wavelength lasers using different periods for the etched holes along the X and the Y directions. The lasers were characterized at different temperatures. The characteristic temperature (T0) for the threshold shift and the temperature dependence of the emission wavelength were studied. As all DFB lasers, our lasers had very small temperature dependence on the wavelength. The polarization of the emitted light was also studied. For the single wavelength lasers, the polarization had no preferred orientation. But for the two wavelength lasers, two clear polarization orientations were clearly observed for the two different wavelengths. The mid-infrared surface emitting lasers are expected to be useful in many different applications, especially in environmental control such as gas sensing. In this thesis, the two wavelength surface emission at this wavelength was reported for the first time. I will provide additional flexibility for sensing applications.