| Summary: | 碩士 === 國立交通大學 === 光電工程所 === 87 === Traditional Polarizing Beam Splitters (PBSs), such as Wollaston Prism and MacNeille Polarizer, have advantage of high extinction ratio, broad band, and high efficiency. However, owing to the inherent nature of their asymmetric properties, these PBSs have small field of incident angle and are in huge volume. In order to overcome this shortage, subwavelength grating is used to design a planar PBS with high efficiency and wide field of incident angle.
Subwavelength gratings can be treated as uniaxial media with large birefringence. Moreover, the birefringence can be controlled through the fill factor of grating. With these properties, it is possible to design the grating so that it forms a dielectric mirror under one polarization, and forms an antireflection coating under another polarization. Moreover, using the multilayer structure, we have designed a planar PBS with an efficiency of 0.97 for both polarizations. Moreover, since the uniaxial behavior of subwavelength grating is almost independent of incident angle, the field of incident angle is as large as ±10 degree.
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