奈米光柵結構應用於3D立體顯示

Abstract

本論文探究如何利用奈米光柵結構製作出不同類型的極化出光元件，使其應用於極化3D立體顯示系統。金屬奈米光柵結構有很高的熱穩定性，適合用於現代的顯示系統。奈米結構分別使用了雷射干涉曝光顯影、電子束曝光顯影與奈米壓印的方式來製作。根據不同的製程方式，我們對應設計出適合的偏光片與四分之一波片。此外，奈米光柵結構也可以當作透明電極使用，並且應用在太陽能電池或是極化出光元件上。本論文主要分為四個部分:線極化出光元件應用於3D顯示，圓極化出光元件應用於3D顯示，使用奈米結構做為透明電極與光柵的影像品質分析。 第一部分，多種不同方式製作出來的奈米光柵被設計用來製作偏光片。當可見光波長在400奈米到700奈米內，偏光片可以讓入射TM波穿透且反射TE波以達成偏光效果。為了確保極化光有高極化率，入射光的穿透頻譜與極化率都事前用嚴格耦合波分析法(RCWA)來進行模擬。當把這個技術應用到有機發光二極體(OLED)，可以製作出有極化出光的綠光OLED與白光OLED，而且極化率可以到達接近90%。 第二部分，本論文使用一個簡單的方法量測兩光軸間的相位差與圓偏振極化光的橢偏率。利用奈米光柵結構設計並且製作窄頻的相位延遲片，穿透光的極化特性也根據理論與實驗結果進行分析。所有圓偏振出光的橢偏率都可以到達接近90%,並且不同相對應的元件彼此之間的交互干擾(cross-talk)都可以低於7%。此外，我們也製作金屬奈米光柵設計的寬頻四分之一波片，因為寬頻四分之一波片在可見光波段都有效，所以此項技術可以簡化3D立體顯示系統的製程。而此寬頻的光柵元件也進一步與線偏振出光OLED結合以達成圓偏振出光OLED的製作。 第三部分，使用嵌入式的光柵結構來保護光柵並且同時當作極化濾波片與透明電極。嵌入式結構的OLED展現高發光效率與高極化率的出光，在未來的3D立體顯示產業有很大的潛力。另一方面，在太陽能電池的應用，奈米光柵透明電極可以增加太陽能電池主動層內的光場強度並且增加主動層的吸收。TM入射波在主動層內可以產生SPP模態而TE入射波則可以激發波導模態。表面電漿式非使用銦錫氧化物(ITO)的有機高分子太陽能電池效率可以達到3.64%。 第四部分，基於上述的研究結果，這邊模擬了極化3D立體顯示系統的影像，以便了解影像品質與交互干擾的關係。此外，相對應的光學系統也架設以模擬實際3D立體顯示系統。為了觀察影像的均勻度，這邊除了使用輝度計外，也實際拍攝了照片。奈米光柵結構的寬頻四分之一波片在雷射3D投影系統應用上將有很大的潛力。

The thesis explores various polarized emitting light source in polarized 3D system application by utilizing nano-grating structures. The temperature stability of the metal nano-grating structures is high, such that it is suitable for the modern display system. The nano-grating structures are fabricated by laser interference lithography, e-beam lithography and nano-imprint process, respectively. According to different fabrication processes, the samples are designed to function as a polarizer or a quarter wave plate. Moreover, nano-structure also works as a transparent electrode, which can be used in solar cell or polarized organic light emitting diode (OLED) devices. The thesis is divided into four primary tasks: linearly polarized OLED for 3D system, circularly polarized OLED for 3D system, nano-grating structure for transparent electrode and the image quality of 3D system based on nano-grating structures. First, the metal nano-grating structures prepared by various fabrication processes are designed to function as a polarization selector to allow transmission for transverse magnetic (TM) wave and reflect transverse electric (TE) wave in the wavelength range of 400-700 nm. The transmission spectra and polarization characteristics of the designed sample are simulated by rigorous coupled wave analysis (RCWA) method to ensure the high polarization ratio of the emission light. By applying this technology to OLEDs, we successfully fabricated a green and a white light OLED with linearly polarized emission. The polarization ratio can reach around 90%. Second, a simple method to measure the phase difference between two optical axis and the ellipticity of the circularly polarized light is demonstrated. The nano-grating structures working as the phase retarder are designed for narrow wavelength band, and then fabricated. The polarized characteristics of transmitted light are estimated theoretically and experimentally. The ellipticity of circularly polarized emission for all samples can reach around 90% and the cross-talk of those of samples are smaller than 7%. In addition, the metal grating quarter wave plate operating in the wavelength range of 400–700 nm is also designed and fabricated. It can simplify the fabrication of 3D system as the sample can function as a phase retarder in visible wavelength range. The nano-grating sample is further combined with linearly polarized OLED to form a circularly polarized OLED. Third, the embedded grating structure is used to protect the grating from damage, and simultaneously function as the polarizing filter and the transparent electrode. The OLED with embedded structure can exhibit highly polarized emission and high efficiency, which has great potential in the future 3D display industries. On the other hand, for the application of the solar cell, the nano-grating transparent electrode is used to enhance the field intensities in the active layer and increase the absorption of the active layer. The TM wave can generate the surface plasmon polariton (SPP) mode, and the TE wave can excite the wave guide mode at the active layer. The power conversion efficiency of the plasmonic ITO-free polymer solar cell can reach as high as 3.64%. Fourth, in terms of previous tasks, the images of the polarized 3D display system are simulated to understand the relation between the image quality and cross-talk. In addition, the optical components are also arranged to simulate the real 3D system. To observe the uniformity of the images, we not only measure the brightness of the images by luminous-meter but also take the photography. The nano-grating quarter wave plate shows a great potential in the application of polarized 3D laser projector system.