室溫下運作之圓極化紫外波段金屬氮化鎵奈米雷射

Abstract

在此論文中，我們展示了在室溫下金屬氮化鎵手性奈米雷射的雷射現象，並分析雷射訊號的圓極化特性。 在第一個部分中，我們設計具有手性之卍字結構金屬共振腔，接下來則使用有限元法近似解模擬工具確認卍字結構金屬共振腔之共震模態，在製程方面，我們以電子束微影系統於未參雜之氮化鎵上定義出左手性以及右手性的卍字結構，並使用乾蝕刻系統將卍字結構轉印至氮化鎵上，最後則鍍上金屬鋁作為金屬共振腔層，接下來以掃描式電子顯微鏡確認所製成之元件是否符合我們所設計。完成製程後，則以Micro-PL系統量測元件的雷射特性，實驗結果發現了我們的室溫雷射波段為三百六十四奈米，且無論左手或右手性結構皆為同樣的波長；我們再藉由量測不同週期陣列的雷射特性，發現波長不因周期的不同而有所變化，因此可以確定雷射特性是由卍字結構金屬共振腔所決定。 論文的第二部分則藉由在Micro-PL系統中增加一個由四分之波板以及線性偏振片以量測雷射訊號的偏振特性，為了區分左手以及右手卍字結構金屬共振腔所產生之偏振特性，我們由計算非對稱因子，確認左手結構和右手結構分別產生左右圓極化光；我們也發現左手結構在左圓光源下擁有較低之閥值能量密度。 綜合以上結果，我們證明卍字結構金屬共振腔具有在室溫下以奈米元件產生圓極化雷射光。

In this thesis, we demonstrate a room temperature operated metal-GaN nanolaser and analysis lasing characteristic and polarization state of it. In the first part, we design our gammadion metal-cavity and use FEM to simulate the electric field mode profile. We then define the left-handed and right-handed gammadion pattern on our undoped GaN by e-beam lithography. We then etch down to GaN layer by ICP and finally we coat Al layer. After fabrication procedure, we use SEM to confirm our device fitting our design. We use micro-photoluminescence system to measure the lasing signal from the gammadion metal-cavity. The measured wavelength of the left-handed and right-handed gammadion metal-cavity are both 364 nm. We also measure the lasing wavelength that emitted from different period gammadion metal-cavity. The measured wavelength from different period gammadion metal-cavities are equal. This result confirms that lasing characteristic is controlled by single gammadion metal-cavity. In the second part, we modify the setup of micro-photoluminescence system by adding a tunable quarter wave plate and a linear polarizer to analyze the polarization state of gammadion metal-cavity. In order to distinguish the polarization difference between left-handed and right-handed gammadion metal-cavity, we calculate dissymmetry factor and find out the polarization state of left-handed and right-handed gammadion metal-cavity are left and right circularly polarized, respectively. We also discover that left-handed gammadion metal-cavity exist lower incident pumping power density under left circularly polarized pumping source. These result shows that we demonstrate a circularly polarized nanolaser by gammadion metal-cavity.