标题: 微极化分光器应用于自由空间型微光学读写头
Micro Ploarization Beam Splitter for Free-Space Micro Optical Pickups
作者: 蔡婉伶
Wang-Ling Tasi
谢汉萍
光电工程学系
关键字: 极化分光器;微光机电;PBS;MOEMS
公开日期: 2004
摘要: 极化分光器在光电系统上是一个很重要的元件,主要用来将光分成两个极化方向互相正交的光束。在光学读写头上,极化分光器扮演一个不可或缺的角色。由光源打出的光经极化分光器后分成横向电波(TE)及横向磁波(TM)模式。一般的极化分光器主要是利用双折射晶体或次波长光栅来建构;但前者有体积大的缺点,而后者的成本则过于昂贵。
本论文主要利用微机电制程技术来设计与制作体积小、重量轻以及相容于自由空间型光学读写头之红光及蓝光波段的微型极化分光器。在设计上,我们利用氮化矽薄膜在可见光区段的高穿透、制程上的高蚀刻选择比及低应力特性来当此分光器之光学薄膜,并藉由微枢纽及止动微结构等辅助定位系统使其垂直于矽基板上。基于布鲁斯特角及光学薄膜的性质,我们可模拟出具有高分光比的微型极化分光器。在制作三维的微元件之前,我们使用制程上较易达成的平面型极化分光器来验证其光学特性是否符合我们的需求。接着利用微机电的面型微加工技术来制作自由空间型的立体极化分光器。量测的结果与预期的相当接近:横向磁波的平均穿透在红光及蓝光波段可达到89%及50%以上,而穿透与反射的极化分光比则大约为9.6及20.9。这表示此极化分光器可有效分离横向磁波及横向电波,而此穿透的横向磁波则可读写光碟片上的资料。此具有高光效率与极化分光比的微型化极化分光器对于应用于光学读写头上是一个可行的途径。
MEMS-based optical pickups offer many advantages over conventional ones, including small size, light weight, high functionality and assembly steps. A free-space micro-optical pickup is consisted of many optical elements, among which polarization beam splitter (PBS) is a key component to split the light into two orthogonally polarized components, transverse electric(TE) and transverse magnetic(TM) modes. However, there is neither thin nor compact PBS that can efficiently produce polarized light and integrate with the free-space system.
The main objective of this thesis is to design and fabricate two types of SiN based micro-PBS: one is for 633 nm wavelength, the other is for 405 nm wavelength system. Silicon nitride membranes of low absorption in the visible wavelength and superior mechanical characteristic of low stress for red and blue ray application were deposited as an optical material. For the micro-optical pickup application, the design target is to have maximum transmittance of TM mode and detectable reflectance of the reflected TE mode. By choosing a proper thickness z of the thin film, the transmitted TM mode and reflective TE mode can be easily turned to be a desired value. A sensitivity analysis was conducted for fabrication and alignment tolerances. Based on the simulations, the planar PBS for demonstrating the properties of the thin film and pop-up PBS were fabricated. At Brewster angle incidence and proper thickness of the thin film, the transmitted TM mode of micro pop-up PBS are 89% and 50 % for red and blue ray spectra, respectively. Therefore, the SiN based micro-PBS has the potential to apply in the micro optical pickup.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT009224559
http://hdl.handle.net/11536/76753
显示于类别:Thesis


文件中的档案:

  1. 455901.pdf
  2. 455902.pdf
  3. 455903.pdf
  4. 455904.pdf
  5. 455905.pdf
  6. 455906.pdf
  7. 455907.pdf
  8. 455908.pdf
  9. 455909.pdf
  10. 455910.pdf
  11. 455911.pdf

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