FRG: Excitation Dynamics and Laser Action in Systems of Pi-Conjugated Materials

University Of Utah, Salt Lake City UT

Investigators

Abstract

This project is a collaborative effort among researchers at the University of Utah Physics De-partment with expertise in Organic Materials Science, Transport and Device Physics, Optics and Optoelectronics, and Theoretical Physics. The project research goals are the synthesis and growth of novel semiconductor pi-conjugated organic crystals and self-assembled polymer thin films; fabrication, applications and theory of organic optoelectronic devices and microlasers with un-usual resonators; and study of the photoexcitation dynamics, laser action and charge carrier prop-erties in these systems. The approach is to study pi-conjugated polymers and long oligomers that form self assembled 2D lamellae and/or other highly planar chain morphologies in spin cast films, as well as novel single crystals of oligomers, acenes, and their alloys. These polymer films and single crystals can be grown with very low defect densities, consequently substantially in-creasing their carrier mobilities. The photogeneration and dynamics of excitons and polaron pairs in the polymer films and single crystals at low excitation intensities, the formation of stimulated emission, laser action and exciton nonlinear processes at high excitation intensities will be stud-ied. Additionally, organic light emitting diodes (OLED) and field effect transistors (FET) will be fabricated using self-assembled polymer films and single crystals, along with study of the prop-erties of carriers injected into the OLED active material and FET channel transistor using a novel spectroscopic technique. A variety of unusual microlaser resonators will be fabricated, tested and investigated experimentally and theoretically. These include randomly formed resonators, which give rise to the phenomenon of random lasers in pi-conjugated films and infiltrated opals; asym-metric resonators that form both chaotic and stable laser modes with improved directionality over existing microdisk laser resonators; and 2D photonic crystals that will be directly patterned onto the organic crystals using electron beam lithography. %%% The project addresses fundamental research issues in topical areas of electronic/photonic materi-als science having technological relevance. An important feature of the project is the strong em-phasis on education, and the integration of research and education. The combined resources, in-cluding crystal growth, polymer synthesis, experimental and theoretical physics methods, device fabrication, processing and testing, provide special opportunities for education and training of post doctoral associates, graduate and undergraduate students involved in highly interdisciplinary forefront research. ***