嵌入量子點之光子晶體微共振腔的製作與分析

Abstract

在本文中，我們將以平面波展開法(Plane Wave Expansion)與有限差分時域法(Finite-Difference Time-Domain)來模擬光子晶體的結構與特性。利用埋有砷化銦鎵 (InGaAs)量子點的主動材料，經過電子束直寫微影技術，以及乾式與溼式蝕刻方式做出二維平板狀光子晶體共振腔。 首先我們改變共振腔大小，發現隨著共振腔增大，所量測到的模態數也越多，並且在越大的共振腔中，迴音廊模態的品質係數有越高的趨勢，接著我們使用特定的共振腔，改變特徵尺寸為變異數，發現隨著孔洞半徑的減小，共振模態往長波長移動，這與我們的理論預期吻合。 我們模擬並實現在六角形對稱共振腔結構中，移動六個孔洞位置使之成為較接近圓形共振腔的結構，實驗證實可以大幅地增加品質係數。在共振腔中心設計直徑為50nm的孔洞，可以削減徑向模態的發生，使之成為單一共振模態。在直線形缺陷共振腔的部分，藉由移動兩邊孔洞的位置，觀察品質係數的改變與模態波長的移動。最後在不同溫度下，發現樣品有效折射率變化導致模態波長的移動與強度的變化。

In this work, we used plane wave expansion and finite-difference time-domain methods to simulate the resonant behavior of photonic crystal cavities. Using InGaAs quantum dots as active material, we have successfully fabricated two dimension photonic crystal slab microcavities by E-beam lithography, dry etching and wet etching techniques. First, we observed that resonant mode numbers and quality factor of whispering gallery modes increase with the cavity sizes. Resonant modes can be controlled by different designs of lattice constants and air hole radii respectively. Second, we have simulated and fabricated photonic crystal cavities with improved quality factors by rearranging the inner holes to form a more circular cavity. We added an air hole with 50nm diameter in center to suppress the side modes. In linear cavities study, we observed that quality factors of resonant mode change when rearranging air holes at both edges. Third, we observed resonant modes at various temperatures, which show red-shift behavior and intensity variation with increasing temperature.