Ultrafast coherent terahertz spectroscopy in high magnetic fields

With an aim towards measuring the high-frequency complex conductivity of correlated electron materials in the regime of low temperatures and high magnetic fields, we introduce a method for performing time-domain terahertz spectroscopy directly in the cryogenic bore of existing dc and pulsed-field magnets. Miniature, fiber-coupled THz emitters and receivers are constructed and are demonstrated to work down to 5 K and up to 6 Tesla, for eventual use in higher-field magnets. Maintaining the sub- micron alignment between fiber and antenna during thermal cycling, and obtaining ultrafast (<200fs) optical gating pulses at the end of long optical fibers constitute the major technical challenges of this project. Preliminary data on YBCO superconducting thin films is shown.