MID-INFRARED AND TERAHERTZ SPECTROSCOPY
The visible/near-infrared (400 nm to ~2 microns; 3.1 eV to 0.62 eV) has been extremely well explored. Lower photon energies, however, are very important for understanding a variety of condensed matter behaviors, such as phonon frequencies, superconducting gaps, intra-excitonic transitions, plasmon frequencies, and inter-subband transitions. Using both mid-infrared (3 to 10 microns; 0.4 to 0.124 eV) and terahertz (150 microns to 1200 microns; 8 meV to 1 meV) sources, we optically investigate physical properties at low energies.
In the Rice lab, we are interested in four research avenues best explored using low photon energy spectroscopy: exciton properties, the photo-spin-voltaic (PSV) effect, InSb quantum dots, and terahertz (THz) generation. The first two are investigated using an optical parametric amplifier (tunable-wavelength, pulsed laser source). For our exciton work, we are interested in using the OPA as a visible source, while measuring the excitonic properties using a terahertz pulsed probe. This system is currently being built in the Pikal lab by Henry Wladkowski and Joe Murphy. For the PSV effect work, which is a collaboration with David Ellsworth and Mingzhong Wu at CSU, we use the OPA as a strong excitation source that can be tuned across a wide wavelength range. This spectral dependence is an important contribution towards understanding the PSV effect. For our InSb work, which is done in conjunction with Ted Kraus and Bruce Parkinson, we use an incoherent source to measure the optical and electrical properties of the InSb quantum dots. Finally, Ying-Hao Chien is using our 1035 nm amplifier to explore new ways of generating THz pulses.