藉由氧化銦錫層之增強光學力於氮化矽波導上進行微米粒子傳輸與分類

Abstract

這篇論文的目標為，在一個光容易耦合進入的波導結構上，增強消逝波與微米粒子的交互作用，以完成高效率且高穩定度的進場粒子傳輸系統。為此目的，我們研究光學作用力隨著實心波導幾何結構的改變。由模擬結果預測，較細薄的波導可以在較短波長處得到較強的推動力，而此推動力直接影響粒子的傳輸效率。為了達到多粒子的平行傳輸，我們必須同時考慮光穿透率與光學推進力；此穿透率為波導上傳遞光通過傳遞粒子後依然於波導上傳遞的比率。透過光穿透率與光學推進力的乘積，我們可以評定一波導結構進行多粒子平行傳輸的能力。為了進一步提升消逝波與粒子的交互作用，我們在波導結構及基板間加入200奈米厚之氧化銦錫層。模擬結果顯示，透過氧化銦錫層的金屬特性，光學作用力可有效的被增強。實驗結果顯示，以功率為一瓦特的光導入波導中，具有氧化銦錫層之0.5微米寬的波導可以以每秒9.65微米的速度傳輸直徑2微米的粒子，這結果是優於較寬的波導所呈現的，其速度更是比不具有氧化銦錫層之波導結構還快許多。此外，具有氧化銦錫層之波導也同時在側向以及垂直方向擁有較大的吸引光學力，可以有效率的捕捉粒子在波導之上的，達到穩定捕捉及傳遞。除此之外，我們也可以藉由與粒子尺寸的不同，所對應的光學力與速度的落差，來進行粒子分類的實驗。

In this thesis, we investigate the dependence of induced optical forces on geometry of solid-core waveguide. Simulation results predict that the thinner and narrower waveguide can transport particles more efficiently at short wavelength. For the parallel-transport system, the force-transmission product we used to verify the ability of particles manipulation of waveguides at the same time. We also find that an indium-tin-oxide (ITO) layer between the waveguide and substrate can further improve the optical forces. Experimental results show that when 1W power is coupled into waveguide, 0.5μm wide waveguide with ITO layer underlaid can transport 2μm particles for 9.65μm/s, which is faster than that on the wider waveguides, and much faster than that on similar without ITO layer underlaid. The waveguide with ITO layer underlaid also have the greater attractive optical force in lateral and vertical direction, then it can trap particles efficiently at the equilibrium point above the waveguide. The particle-size dependent forces are used in the sorting experiments, and we can separate en-mass particles in practical system.