EAGER: Collaborative Proposal: R-Optics, Light in the Optical "No-Man's Land"

University Of Notre Dame, Notre Dame IN

Investigators

Abstract

Abstract Title: Novel Approaches for Generating and Controlling Light in the Optical No-Man's Land of the Far-IR Abstract Content: Nontechnical: The Reststrahlen Band is the portion of the optical spectrum where materials have strong absorption of light resulting from collective vibrations of the crystal lattice. Though this band varies between materials, it generally falls between the wavelengths of 20-60 microns, and has effectively precluded the development of any significant optical infrastructure in this far-IR portion of the optical spectrum. In some sense, the Reststrahlen Band is one of the last optical frontiers. This EAGER program's innovative approach lies not only in our efforts to build a tool-set for the development of optical and optoelectronic materials and devices in the Reststrahlen band, but also in its goal of laying the foundation for further Reststrahlen band exploration by delineating a set of potential R-Optics applications and technologies. In doing so, our desire is to build the framework of an optical infrastructure for this unexplored wavelength range, demonstrating techniques for generating, manipulating, and controlling light at these long wavelengths, but also developing an understanding of the potential applications of such long-wavelength optical and optoelectronic devices for a variety of biological, chemical, medical and defense applications. Technical: The primary thrust of the EAGER will be an integrated theoretical, computational, and experimental effort to (a) demonstrate phonon-enhanced thermal emission from a range of material systems, and improve phonon-assisted light collection using self-focusing and steering surfaces, (b) expand coverage of the Reststrahlen band by i) control of free-carriers to tailor the permittivity of phononic materials and ii) isotope engineering in GaN, and (c) generate and detect optical emission from non-equilibrium phonon populations in semiconductor quantum-cascade-like devices, for the potential development of electrically-pumped Reststrahlen band sources. We will develop spatially and spectrally selective thermal sources in the Reststrahlen band, as well as mechanisms for controlling materials' Reststrahlen band optical properties. At the same time, we will look to demonstrate sources based on quasiparticle generation using quantum cascade-like devices. We will also investigate a range of material systems in order to build a library of materials (and material properties) for the development of composite optical materials for Reststrahlen band applications. Many, though not all, of our devices and materials will be grown by Molecular Beam Epitaxy, and all materials and composites will be characterized by Fourier transform infrared and Raman spectroscopy, as a function of temperature, material composition and/or geometry, and electrical (or optical) pumping power. The end result of the 18-month EAGER is ambitious: the development of an optical and optoelectronic foundation and framework for a heretofore underserved and mostly avoided wavelength range.