Guoliang Chen

Graduation Semester and Year

2015

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Electrical Engineering

Department

Electrical Engineering

First Advisor

Robert Magnusson

Abstract

Guided-mode resonance (GMR) effect based on waveguide grating structure has been attracting plenty of attention in recent years due to its abundant application in energy, information technology, and sensors. This dissertation aims to develop new GMR devices and apply them in the above fields. Initially thermoelectric devices integrated with optical resonance absorbers are demonstrated. We design the absorbers with rigorous numerical methods and fashion experimental prototypes by thin-film deposition, patterning, and etching. A ~2.5-?m-thick p-type heavily doped polysilicon film on a ~2-?m layer of thermally grown SiO2 enables guided-mode resonance. The SiO2 layer additionally serves to thermally insulate the polysilicon layer from the Si substrate. A grating layer is etched into the polysilicon film to form the absorber. Thus, the polysilicon film works as functional material for both the absorber and the thermoelectric converter itself. Numerical simulations show that the resonance segment enhances absorption by ~30% in the visible spectral range and by ~40% in the infrared range relative to unpatterned devices. Moreover, experimental results demonstrate significantly increased electrical output over reference devices. These simple devices can be applied as compact voltage generators and IR sensors. Thereafter GMR multiline devices are investigated. As a preliminary study a glass-sub multiline guided-mode resonance (GMR) filter is applied as a reflector to implement an external cavity laser. We design the resonant element using rigorous numerical methods and fashion an experimental prototype by thin-film deposition, patterning, and etching. A ~100-nm TiO2 grating layer on a ~170-µm-thick glass slab supports thousands of resonant modes. We detect ~10 narrow resonance peaks within a ~10-nm wavelength range centered at the 840-nm wavelength. We apply this multiline GMR device to a gain chip and obtain several simultaneous resonant laser lines that compete for the gain. Precise tuning enables a stable laser line that can be selected from the multiple available resonant lines. Furthermore we investigate GMR multiline devices in more details and with better performances. GMR multiline filters exhibiting resonance lines on a dense spectral grid in a broad near infrared (NIR) wavelength range are demonstrated. We design the filters using rigorous numerical methods and then proceed with experimental verification by patterning, etching, and collecting spectral data. In one embodiment, we design and fabricate thick Si slab-based multiline filters within a wavelength range centered at the 1550 nm with potential application in high sensitivity gas sensors and signal processing system. Devices with two types of gratings, Si grating and TiO2 grating, are demonstrated experimentally with TiO2 grating devices exhibiting better performances. For TiO2 grating devices we can detect 12 narrow resonance peaks within a 10 nm wavelength range centered at the 1550 nm. The spectral width of each resonance peak is ~0.1 nm with free spectral range of ~0.8 nm. High efficiency of ~0.9 and low sideband of ~0.01 can be obtained for individual device output. Design of polarization independent multiline filter and Brewster multiline filter are also presented.Finally, we apply GMR devices to implement the return-to-zero (RZ) and non-return-to-zero (NRZ) formats conversion. We realize the conversion by 2 solutions. In solution 1 RZtoNRZ conversion is done by 2 cascading filters – GMR multiline filter and Gauss filter. We simulate the complete conversion flow using Matlab and the spectral data of GMR multiline device is directly input into the Matlab codes. We successfully obtain converted NRZ signal. In solution 2 we prove that an individual filter possessing Gaussian shape can also realize the conversion. Furthermore we design GMR filters to possess spectral shape matched to the referred optimal FBG filter spectrum. By doing this we can theoretically prove that one individual GMR filter (reflection or transmission) can implement RZtoNRZ conversion with good performance.

Disciplines

Electrical and Computer Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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