超快雷射於電漿子超穎物質之製作與操控

Abstract

電漿子超穎物質乃是一種人造次波長週期性結構所組成，其光學性質主要由組成之奈米結構之幾何參數所決定。藉由各種超穎物質的奇特電磁波共振性質近年來人們在光學領域已經實現許多重要且有趣的應用，例如負折射材料、隱形斗篷、電漿子奈米雷射、以及生醫感測晶片。本論文將研究利用超快雷射於多層電漿子超穎物質的製作以及主動式調控兩個應用。在多層超穎物質製作上採用接觸式超快雷射轉印術加工由金及介電質交疊之奈米薄膜來製作多層裂環共振器。利用傅立葉光譜以及數值計算證實此超穎物質具有良好的光學共振效應，也觀察到超穎物質裂環共振器層與層之間的近場耦合效應。在利用超快雷射主動式調控超穎物質的震盪方面，超快雷射脈衝可用來操控超穎物質之共振，兩道反向但同調之超快雷射脈衝可於空間中相距四分之一波長的位置分別形成電場之極大值及磁場之極大值。當超穎物質放製於此系統中時，超穎物質所具有之多極矩共振將會被選擇性的放大或是抑制，端看此時兩道脈衝之間的相位差在空間中形成之電磁場分佈。此外，亦可用此技術來探討超穎物質隱藏於電偶極矩下之複雜多極矩共振行為。此操控超穎物質的技術稱為同調性選擇激發光譜學。此技術可以用來作為主動式的光操控。超穎物質極薄且次波長的單位元，且不需要用到非線性效應便得以用光操縱光，因此具有很大的應用潛力。

Plasmonic metamaterials as a novel class of artificially engineered nanostructures exhibit unconventional optical responses and applications, such as negative refraction, super-resolution imaging, photonic nanolasers, chiral optics components, and biosensors. In this thesis an ultrafast laser is utilized in two applications - fabrication and active control of multilayered plasmonic metamaterials. Contact-mode laser induced forward transfer technique is employed to fabricate arrays of multilayered split ring resonators in which the layered structures are composed of gold/dielectric/gold thin films. Optical measurement reveals rich resonance properties and coupling between split ring resonators of the fabricated metamaterials. The active control of the plasmonic metamaterials by ultrafast laser utilizes two counter-propagating ultrafast laser pulses that form local electric and magnetic field maxima in nearby free space. Under excitation of a particular condition, a certain group of multipolar resonances from the metamaterial are amplified while others are suppressed at the maximum of electric or magnetic field. Using this technique, we were able to reveal the hidden resonance modes of metamaterials which allowed us to gain understanding of these features that are otherwise difficult to study. This technique opens an important pathway for developing novel plasmonic metamaterials and exploring their associated properties.