High power GaInAs photoconductive terahertz radiation source

Rensselaer Polytechnic Institute, Troy NY

Investigators

Abstract

Objective: Our objective is the development of a compact sub-picosecond THz-radiation source for time-domain (TD) THz spectroscopy and THz-imaging with an average power of 1mW operating at MHz repetition rates. Intellectual merit: The approach utilizes voltage-biased THz-emitters made from ternary and quaternary alloyed semiconductors driven by multi watt mode-locked Ytterbium (Yb) lasers. Unique crystal growth by Vertical Bridgman and Vertical Gradient Freezing Methods with accelerated crucible rotation technique will be used to produce crystals with high-resistivity (104-107?Çcm), high-mobility (3000-5000 cm2/Vs) and femtosecond carrier lifetimes as well as variable band gaps between 0.4eV to 1.5eV. Materials grown from melt will provide superior electrical and optical properties due to the near-equilibrium growth process compared to thin films grown from vapor or solid phases. The energy band gap of ternary and quaternary alloyed semiconductors can be perfectly matched to the emission wavelengths of Yb-lasers in the 1000-1100nm band. Broader impact: The proposed research integrates research and education through curriculum enhancement as well as undergraduate and graduate students¡¦ research participation. Outreach to undergraduate students from non-PhD-granting institutions will be practiced through a summer REU program. Another strong focus will be outreach to minorities underrepresented in science and engineering and recruiting of these students for our research. The proposed research will advance applications of time-domain THz- spectroscopy and imaging in research and industries across a broad range of disciplines through brighter emitters and compact THz-systems. Time-domain THz technology will be one key application of multi watt mode-locked Ytterbium lasers in the future.