研究純量與向量結構光及與層狀二硫化鉬之交互作用

Scalar and Vector Structured Light: Generation and Interaction with Layered Molybdenum Disulfide

黃騰德(Teng-De Huang)

指導教授 ： 陸亭樺

國立臺灣師範大學/理學院/物理學系/博士(2020年)

https://doi.org/10.6345/NTNU202000169

摘要

角動量雷射為具有光學軌道角動量、螺旋型的波前與相位分布及光旋渦之雷射光，其擁有與傳統雷射截然不同的空間分布及光學特性。將不同參數之角動量雷射做疊加，能製造單一光場擁有多個光旋渦之光源。因角動量雷射的參數可以不斷增加，與傳統控制光學偏振及其基本參數的實驗相比，前者多了更高的自由度，也不易受到實驗上的侷限。角動量雷射具有的特殊性質，在不同領域中，它能提供不同的應用價值。舉例來說，討論光學操控(optical manipulation)的領域時，角動量雷射由於螺旋型的波前以及其特有的波印亭向量(Poynting vector)，使其能產生光力矩(optical torque)並抓住粒子，且帶動粒子隨著其強度分布做逆時針或順時針的旋轉，而其方向取決於角動量雷射的參數。討論光通訊的領域時，角動量雷射能攜帶比傳統雷射更高的資訊量。傳統光纖通訊，使用時間範疇(time domain)的方式(1或0)，1為光傳播訊號，0為光不傳播訊號。藉由此方式傳播數據，需有很大的重複率來提高傳播速度，而角動量雷射能在採取1的動作時，給予更高的資訊量，進而提高整體傳播速度。另外，角動量雷射也能應用在大氣傳播中(free propagation)，因其具有特殊的螺旋型波前，使其不易受到空氣擾動(air turbulence)的影響，進而能進行遠距離的傳播，再者，若將角動量雷射與空間非齊性(space-inhomogeneous)的偏振分佈做結合(向量場之角動量雷射)，更能提高其傳播效率。角動量雷射也能應用於量子解密或量子糾纏中，此應用在未來通訊協定或是宇宙科學的方面都提供很高的應用潛力。因此，利用不同光學系統製造空間齊性偏振分佈(Scalar beam)及空間非齊性(Vector beam)的角動量雷射為本論文的重要工作。在本論文中，空間齊性偏振分佈的角動量雷射能藉由半柱面型共振腔搭配腔外柱透鏡、空間光調制器搭配電腦產生之全像片(computer-generated hologram)來產生。另一方面，空間非齊性的角動量雷射可以藉由共振腔及空間光調制器與其他光學元件的結合來產生。如: 干涉儀、四分之一波片等…。另外，我們也將產生之角動量雷射光源與層狀二維材料做結合，探究其特有光學特性與材料交互作用後，產生的光致發光及聲子震動(拉曼光譜)，進而研究產生的物理甚至與元件的製程做連接。

關鍵字

光旋渦雷射 ； 光學軌道角動量 ； 偏振 ； 純量及向量結構光

並列摘要

Structured light possesses properties such as orbital angular momentum (OAM), spiral wavefront, spiral phase, and optical vortex. The crucial properties of the generated beams extend its potential applications to various research fields, such as optical manipulation, optical communication, and optical cryptography.
In general, a scalar structured light, which is an optical field with space-homogenous polarized distribution, is directly generated either from a spatial light modulator (SLM) with computer-generated holograms (CGHs) or a hemi-cylindrical resonator with an extra-resonator cylindrical lens. The order of the structured light is determined by the different grating phase of the structured light, as well as the pump offset and defocus magnitude of the laser resonator, respectively. On the other hand, a vector structured light, which is an optical field with space-inhomogeneous polarized distribution, is passively generated by combining the SLM with other optical systems such as Mach-Zehnder interferometer, dove prism, and optical retarder. It could also be directly generated from the vortex phase plate (VPP). Structured light with space-inhomogeneous polarized distribution provides an extra degree of freedom to further extend its potential applications. All states of polarization of the scalar and vector structured light are described by the fundamental Poincaré sphere and high-order Poincaré sphere (HOPs).
Meanwhile, the scalar and vector structured light beam have been utilized to interact with layered Molybdenum Disulfide (MoS2). The resulting phonon behavior in the material is analyzed using polarized Raman spectroscopy, which shows that the symmetry of the phonon can be broken by using elliptically polarized light. The exciton behavior in the layered material is also observed via the optical spectra induced by the light-matter interaction, which demonstrates that the photon energy is increased when the order of structured light is incremented. These results introduce a probable increase of the degree of freedom in various material science applications.

並列關鍵字

twisted light ； optical orbital angular momentum ； polarization ； scalar or vector structured light

參考文獻

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