IMR: Acquisition of an Amplified Ultrafast Laser System for Terahertz Spectroscopic Research and Student Training

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The award from the Instrumentation for Materials Research program (IMR) will be used to acquire an amplified femtosecond laser system. The availability of such pulsed visible radiation will open up exceptional opportunities for the utilization of intense pulsed electromagnetic radiation, both optical and far-infrared. This latter spectral region is of great scientific and technological significance, but high-intensity coherent radiation for spectroscopic measurements has typically only been available from sources such as synchrotrons or free-electron lasers. The production of high-intensity radiation in the far- to mid-infrared will be accomplished via optical rectification of the visible laser pulses. This method will produce single-cycle electromagnetic pulses with spectral content extending beyond 30 THz. In addition to allowing research on the physics and fundamental limitations of these nonlinear optical frequency conversion processes, the requested equipment will permit important new spectroscopic techniques to be developed. The primary areas of application planned for these enhanced capabilities are to the study of both dynamic and nonlinear processes in a variety of materials, including both electronic and biological. In addition to the impact that the laser system will have on the PI's research effort, the unique capabilities of a high-intensity broadband terahertz spectroscopic system will enhance and expand collaborative opportunities with members of the Physics, Chemistry, Materials Science and Engineering, Biology, and Electrical and Computer Engineering Departments. The broader impact of these interactions is related primarily to the research training of students from many different disciplines. The award from the Instrumentation for Materials Research program (IMR) supports the acquisistion of an amplified femtosecond laser system. The availability of such pulsed visible radiation will open up exceptional opportunities for the utilization of intense pulsed electromagnetic radiation, both optical and far-infrared. This latter spectral region is of great scientific and technological significance, but high-intensity coherent radiation for spectroscopic measurements has typically only been available from sources such as synchrotrons or free-electron lasers. The production of high-intensity radiation in the far- to mid-infrared will be accomplished via optical rectification of the visible laser pulses. This method will produce single-cycle electromagnetic pulses with spectral content extending beyond 30 THz (i.e., 1000 cm-1). The primary goal of the research effort will be in developing new and unique spectroscopic applications that allow for the measurement of materials properties that were previously difficult or impossible. Linear time-domain terahertz spectroscopy is a technique that has been well developed over the last decade to measure the linear, static dielectric properties of a medium. However, there is a relative paucity of data involving the application of time-resolved terahertz spectroscopic measurements or nonlinear THz spectroscopy. In the former technique, one can probe electronic charge transport in a wide variety of materials, such as liquids, insulators, and quantum dots. The technique is all-optical, no electrical contacts are required, and the approach can be applied to materials exhibiting low intrinsic conductivity or short recombination lifetimes. These capabilities are expected to yield valuable information that includes the properties of the nonlinear susceptibility in the far-infrared. When applied to liquids, the approach will yield valuable information about the timescale for orientation relaxation. In addition to the impact that the laser system will have on the PI's research effort, the unique capabilities of a high-intensity broadband terahertz spectroscopic system will enhance and expand collaborative opportunities with members of the Physics, Chemistry, Materials Science and Engineering, Biology, and Electrical and Computer Engineering Departments. The broader impact of these interactions is related primarily to the research training of students from many different disciplines.