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|Type of Document
||Study of Polarization Independent Spatial Light Modulator and Optical Vortex Applications|
|Date of Defense
Spatial light modulator
||Spatial light modulator (SLM) is an electro-optic device possessing high spatial resolution of birefringent pixels. Each pixel can be controlled individually by the signals sent from the computer. Therefore, SLM is capable of modulating the spatial distribution of phase, amplitude and polarization of the incident beam, leading to plenty applications in optics and photonics, such as micro-projection and optical tweezers. |
This study aims to improve SLM particularly for the use in phase modulation and explore their possible applications in spatial control of optical field. Most of the liquid-crystal-on-silicon (LCoS) based SLMs utilize nematic liquid crystals as their host media. Nematic liquid crystals nevertheless possess intrinsic restrictions including polarization-dependent modulation and slow electro-optic response. Polymer-stabilized blue phase (PSBP) liquid crystals emerge as a promising candidate for SLM because of their optical isotropy and sub-millisecond switching. However, the required operating voltage of current commercially available PSBP materials is still too high for SLMs. In this work, we optimized the recipe and polymerization conditions of PSBP and finally demonstrated diffraction experiments using the phase grating generated by a PSBP-based SLM. The experimental findings revealed polarization-independent and ultrafast phase modulation.
The latter part of the thesis describes simultaneous investigations on complex optical vortices generation exploiting the ability of SLM in spatial phase modulation. An optical vortex is a beam carrying an orbital angular momentum and so exhibiting helical wavefront. Using a high-resolution SLM, we were able to convert a Gaussian beam to a vortex beam carrying various orbital angular momenta. Interferometric measurements were applied to verify the vortex nature of the generated beams. In such vortex beams, different orbital angular momenta interfere with each other, thereby forming complex spatial intensity distribution. This makes SLM a more powerful technique in spatial shaping of light fields. The experimental findings agree well with the simulation results. We also demonstrate signal processing of the vortex beams with the SLM acting as both coding and decoding tools. It is believed that further development of the host PSBP materials and complex optical vortices will lead SLMs to a much wider range of practical applications in both the industries and academics.
||Andy Ying-Guey, Fuh - chair|
Shie-Chang Jeng - co-chair
Chi-Yen Huang - co-chair
Tsung-hsien Lin - advisor
Indicate in-campus at 5 year and off-campus access at 5 year.|
|Date of Submission