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Title:Investigation of physical and electro-optic diffractive structures for energy-efficient smart window applications
Author(s):Jang, Linus
Director of Research:Jain, Kanti
Doctoral Committee Chair(s):Rogers, John A.
Doctoral Committee Member(s):Jain, Kanti; Geil, Phillip H.; Sottos, Nancy R.; Eden, James G.
Department / Program:Materials Science & Engineerng
Discipline:Materials Science & Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Energy-Efficient Smart Window
Spectral Selectivity
Blazed Diffraction Grating
Liquid Crystal Light Modulation
Microelectronic Fabrication
Excimer Laser Photoablation
Abstract:The cost of energy used for lighting, heating, and cooling in commercial and residential buildings is increasing annually while wasteful losses and gains through inefficient windows can be avoidable with advanced technology. Energy-efficient smart windows in commercial and residential buildings can reduce energy consumption for temperature control and lighting, potentially saving billions of dollars in heating, cooling, and lighting costs. A smart window is so named for its ability to have control over the window’s optical properties such that they adapt to changing environments. A wide variety of technologies to improve window efficiency have been researched to date, including various mechanical and optical methods, but none has shown the ability to efficiently reject or admit solar heat when desired while retaining daylight that is useful for indoor lighting. To overcome the limitations of current window technologies in providing control over both visible and near-infrared radiation, a novel smart window technology is described that incorporates both physical and electro-optic blazed diffractive components for the control of solar heat while retaining natural light. The optical behavior of physical diffractive structures in different configurations to optimize design parameters such as spatial frequency, groove angle, and angle of incidence are investigated by both theoretical and experimental approaches. Predictive optical models that agree well with experimental results are developed to design the diffractive components for the smart window with high-efficiency. A novel fabrication technique, which offers a low-cost approach with customizability of grating pitch and grating angle, for physical blazed gratings using angled photoablation and in-situ masking is also developed. Based on the results from physical blazed gratings, the novel concept is extended to electro-optic diffractive structures that can be incorporated into energy-efficient adaptive window systems with the desired user controllability. The continuous triangular groove profile of the physical blazed grating is approximated by a 4-step binary profile which is realized by an array of blazed elements each with a 4 x 4 array of passive matrix pixels. Extensive optical modeling and simulation performed using advanced optical design software further confirmed the functionality of selective transmission of the near infrared radiation and indicated the feasibility of the electro-optic diffractive components for smart window technology. Microelectronic fabrication processes for the pixelated optoelectronic smart window based on liquid crystal polymer blazed diffraction gratings are also explored and developed.
Issue Date:2011-06-27
Rights Information:Copyright 2010 Linus Jang
Date Available in IDEALS:2011-06-27
Date Deposited:2010-12

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