Type of Document Dissertation Author Wang, Huazhong URN etd-11092009-011104 Title Study of 2-D Square Rod-in-Air Photonic Crystal Optical Switch and Design of Fast Planar Laser Shutter Degree Doctor of Philosophy Department Electrical and Computer Engineering, Department of Advisory Committee
Advisor Name Title Jim P Zheng Committee Chair Hui Li Committee Member Petru Andrei Committee Member Jim Cao University Representative Keywords
- Pockels cell
- Laser shutter
- Optical switch
- Photonic crystal
Date of Defense 2009-03-04 Availability unrestricted AbstractThis dissertation is made of two parts. Part I, chapter 1 to chapter 7, is 2-D square rod-in-air photonic crystal optical switch; Part II, chapter 8 to chapter 12, is design of fast laser shutter.
Photonic crystal is a kind of materials with periodic structures. Moreover the lattice constant of photonic crystals is on the same scale as the wavelength of electromagnetic waves. One of photonic crystal’s specific properties is that only allowable electromagnetic wave states could propagate inside. This property presents a new way of controlling the propagation of light inside materials. In this paper, a 2-D photonic crystal optical switch is proposed. This is a rods-in-air structure device by removing two cross-lines of rods from a 2-D square-rod photonic crystal. The optical switch feature is achieved by inserting a single rod along the line segment from (-0.7, -0.7) to (0.7, 0.7) in coordinate. In fact, this line segment is the diagonal line of the intersection area of two removed cross-lines of rods. The position of the inserted single rod determines how much the total source energy propagates into the upper channel. In the case of transverse magnetic Gaussian point source, up to 41.38% of the total source energy goes into the upper channel and is shown by time domain simulation. It is also found that the magnitude of the reflected wave in the left channel varies greatly with spatial position of the single inserted rod. The larger the magnitude of the reflected wave in the left channel, the less energy goes into the upper channel. The time delay between the incident wave and the reflected wave in the left channel is also related to the position of the single inserted rod. In addition, the extremely large time delay between the incident wave and the reflected wave in the left channel shows that the reflected wave encounters many reflections with the walls of the left channel, instead of reflected back from the single inserted rod directly. Simulations also demonstrate that the control effect of this 2-D photonic crystal optical switch exists under the cases of Gaussian/continuous wave, point/line source. The advantage of this photonic crystal optical switch presented here is operational simplicity because the change of the position of only one rod is needed to finish the switching function. This operational simplicity is critical in microoptoelectromechanical system (MOEMS) device. Consequently, this 2-D photonic crystal optical switch is an attractive design in the study of integrating optical circuit.
The goal of Part II is to design a laser shutter to protect eyes from fast laser pulse. The width of targeted laser pulse is 30 ns. It is proposed to apply Pockels cell intensity modulator with longitudinal configuration to block the laser pulse. The Pockels cell material is Deuterated Potassium Dihydrogen Phosphate KD2PO4 (DKDP) because its electrooptic parameter, r63, is highest among popular nonlinear electrooptic materials. The laser shutter is controlled by a semiconductor photon sensor. When photon sensor probes laser pulse, laser shutter starts to block off the laser pulse. The performance of laser shutter is also investigted under variant condictions: laser pulse intensity, semiconductor carrier lifetime, size of Pockels cell.
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