以由下而上的方法製作二氧化鈦量子點微碟共振腔

Abstract

本論文中，我們利用由下而上的微碟製作方法，成功製作出具有圓周邊緣不被乾蝕刻之二氧化鈦微碟共振腔，圓周邊緣不被乾蝕刻能使光在內部繞行時，較不被邊緣的粗糙面影響，可以完好的在內部進行全反射並減少散射損耗，使品質因子上升，但在實驗過程中我們發現利用此法製作出的微碟會有變形的情況，導致輻射損耗，因此我們會討論不同程度變形下的Q值表現情形。我們以U型錐形光纖耦合的方式進行Q值的量測，以中心波長1330nm超輻射二極體(Super Luminescent Diode, SLD)進行傳輸頻譜量測，其中直徑20μm，厚度400nm二氧化鈦微碟，在傳輸頻譜的量測下，Q值為600。 接著我們將由下而上的微碟製作方法應用於量子點微碟共振腔元件，以硒化鎘/硫化鋅膠狀量子點做為主動層材料，利用二氧化鈦薄膜上下包覆量子點形成三明治結構，製作出不被蝕刻影響的的量子點微碟共振腔。量測上我們使用波長在532nm的Nd:YAG固態雷射作為激發光源，在室溫下以連續式綠光雷射激發微碟共振腔，其中直徑20μm，厚度250nm，在過程中，我們可觀察到迴音廊模態產生，但未能實現紅光雷射。

In this paper, we successfully fabricated titanium dioxide microdisk resonators using a bottom-up microfabrication approach to ensure that the circumferential edge was not affected by dry etching. This edge preservation minimizes the impact of rough surfaces on light circulating within the resonator, which enables effective internal total reflection and reduces scattering losses, thus increasing the quality factor (Q). However, during the experiment, we observed deformation in the microdisks produced using this method, resulting in radiation losses. Therefore, we discuss the performance of the Q factor under varying degrees of deformation. We measured the Q factor using a U-shaped tapered optical fiber coupling method and employed a 1330 nm Super Luminescent Diode (SLD) for transmission spectrum measurements. For a titanium dioxide microdisk with a diameter of 20 μm and a thickness of 400 nm, the Q factor measured in the transmission spectrum was 600. Subsequently, we applied the bottom-up microdisk fabrication method to quantum dot microdisk resonator devices. We also utilized cadmium selenide/zinc sulfide colloidal quantum dots as the active layer material. A sandwich structure of quantum dots encapsulated between titanium dioxide thin films was fabricated to form quantum dot microdisk resonators resistant to etching effects. For measurement, we used a continuous green laser at 532 nm wavelength from a Nd:YAG solid-state laser as the excitation source at room temperature. We observed whispering gallery modes during the excitation of the microdisk resonator with a green laser, but red laser operation did not materialize .