The goal of this project is to learn to control the flow of light and the conversion of light energy into other forms of energy (and vice versa). This project is fundamental physics research that supports the mission of DOE in the areas of energy-efficient lighting, efficient solar energy utilization, and thermophotovoltaics. Research in this Project can be grouped into two sub-tasks.
Photonic Crystal Physics
Photonic band gap materials are artificially designed periodic dielectric or metallic structures with high refractive-index contrast that can be used to control light (photons) in a manner similar to that used by semiconductors to control electrons. Although this research project originated from theoretical work, its emphasis now is on physical manifestations and tests of the theory. Over the next three years research goals within this subtask will focus on:
- Wide area fabrication of photonic crystal and polymer waveguide structures using reasonable-cost soft lithography techniques (K. Constant, W. Leung, K.-M. Ho).
- Study of fundamental photonic crystal properties including tailored thermal emission, beam steering and focusing (R. Biswas, K. Constant, C. Soukoulis, W. Leung, K.-M. Ho).
- Development of highly efficient algorithms for design and study of devices using photonic crystals. Extension of techniques to study non-linear systems or systems with gain as well as the effects of disorder/fabrication defects on the performance of photonic crystal structures. (C. Soukoulis, K.-M. Ho)
Organic Semiconductor Physics
The goal of this subtask is to provide the fundamental physics underpinning necessary to understand and optimize the performance of organic light-emitting devices (OLEDs) at both low and high brightness. More specifically, the goal is to elucidate the interactions (particularly the spin-dependent interactions) between singlet excitons (SEs), triplet excitons (TEs), polarons, bipolarons, and trions, as they impact the optical and transport properties of these materials and devices. For example, our past experimental work has revealed the central role of TEs and polarons in quenching the SEs, thus decreasing the photoluminescence quantum yield of the films and the internal quantum efficiency of OLEDs. Indeed, these quenching processes are now recognized as the source of the decreasing efficiency of OLEDs at high injection current.
Over the next three years research within this subtask will focus on fundamental studies on novel OLED structures, including n-stacked (tandem) OLEDs, graded junction OLEDs, and hybrid polymer/small molecular OLEDs. (J. Shinar).
Decker M; Ruther M; Kriegler C E; Zhou J; Soukoulis C M; Linden S; Wegener M . 2009. Strong optical activity from twisted-cross photonic metamaterials. Optics Letters. 34:2501-2503.
Vantarakis G; Mathioudakis C; Kopidakis G; Wang C Z; Ho K M; Kelires P C . 2009. Interfacial disorder and optoelectronic properties of diamond nanocrystals. Physical Review B. 80:045307.
Ye Z; Hu X H; Li M; Ho K M; Cao J R; Miyawaki M . 2009. Localized optical orbital approach to study localized states of light in photonic crystals. Physical Review B. 80:035111.
Stieler D; Barsic A; Tuttle G; Li M; Ho K M . 2009. Effects of defect permittivity on resonant frequency and mode shape in the three-dimensional woodpile photonic crystal. Journal of Applied Physics. 105:103109.
Stieler D; Barsic A; Biswas R; Tuttle G; Ho K M . 2009. A planar four-port channel drop filter in the three-dimensional woodpile photonic crystal. Optics Express. 17:6128-6133.
Guney D O; Koschny T; Kafesaki M; Soukoulis C A . 2009. Connected bulk negative index photonic metamaterials. Optics Letters. 34:506-508.
Tapalian H C; Langseth J; Chen Y; Anderegg J W; Shinar J . 2008. Ultrafast laser direct-write actuable microstructures. Applied Physics Letters. 93:243304.
Chen Y; Cai M; Xiao T; Hellerich E; Shinar J . 2008. Optically Detected Magnetic Resonance (ODMR) Studies of Trions in Organic Light-Emitting Materials and OLEDs, and Their Possible Relation to Long-Term OLED Degradation - art. no. 70510G. Organic Light Emitting Materials and Devices Xii. 7051:G510-G510666.