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We report measurements of terahertz (THz) frequency radiation pulses emitted by photoconducting (PC) antennas fabricated from high-resistivity Fe-doped Ga0.69In0.31As. The Ga0.69In0.31As:Fe was grown using a hybrid vertical Bridgman and gradient freezing directional solidification process. GaxIn1−xAs crystals were uniformly doped with Fe atoms to obtain high-resistivity (∼107 Ω cm). The ultrafast carrier mobility in this material is about three orders of magnitude higher than in GaxIn1−xAs thin films grown by molecular beam epitaxy. The bandgap of Ga0.69In0.31As:Fe is low enough (∼1 eV) to use compact Yb-based multiwatt lasers operating at 1.1 μm for photoexcitation of Ga0.69In0.31As based PC antennas for high power THz emission.

Ex vivo and in vivo studies of human skin using reflected terahertz radiation (THz) have revealed that THz has potential for use in medical diagnosis of skin diseases. Detected signals could be enhanced via the application of creams or oils. This idea is similar to that in therapeutic ultrasound: hydrophilic gels improve the coupling of the acoustic wave to the stratum corneum (SC). The use of creams or oils to enhance THz coupling to the SC has not been previously explored. This paper elucidates the impact of two types of commercially available ointment on three different pseudo-skin phantoms at THz frequencies.