Abstract-Surface-phonon-polariton-mediated photon response of terahertz quantum-well infrared photodetectors

DiXiang Shao, XuGuang Guo, YiMing Zhu, SongLin Zhuang, ZhangLong Fu,  JunCheng Cao

http://iopscience.iop.org/article/10.1088/1361-6463/aaeb77/meta

A surface-phonon-polariton (SPHP)-mediated photon response near the longitudinal optical (LO) phonon frequency of GaAs is investigated in a terahertz GaAs/AlGaAs quantum-well infrared photodetector, integrated with a one-dimensional metal grating. For a contrast device without a grating coupler, no SPHP-related signature is found in the photocurrent spectrum, because the incident radiation from free space cannot excite the SPHP, due to the mismatch of momentum. The intensity of the electric field component along the growth direction of the device absorption layer is numerically calculated. The results show that the photocurrent response peaks near the LO phonon frequency band (8.8–9.0 THz) are attributed to the local field enhancement induced by SPHP. Our results are useful to realize high performance SPHP-mediated terahertz photodetectors and other related terahertz devices.

Abstract-Near-Field Infrared Pump–Probe Imaging of Surface Phonon Coupling in Boron Nitride Nanotubes

Leonid Gilburd†, Xiaoji G. Xu†‡, Yoshio Bando§, Dmitri Golberg§, and Gilbert C. Walker*†

† Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada

‡ Department of Chemistry, Lehigh University, 6 East Packer Avenue, Bethlehem, Pennsylvania 18015, United States

§ National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044, Japan

J. Phys. Chem. Lett., 2016, 7, pp 289–294

DOI: 10.1021/acs.jpclett.5b02438

Publication Date (Web): January 4, 2016

Copyright © 2016 American Chemical Society

*E-mail: gwalker@chem.utoronto.ca.

http://pubs.acs.org/doi/abs/10.1021/acs.jpclett.5b02438

Surface phonon modes are lattice vibrational modes of a solid surface. Two common surface modes, called longitudinal and transverse optical modes, exhibit lattice vibration along or perpendicular to the direction of the wave. We report a two-color, infrared pump-infrared probe technique based on scattering type near-field optical microscopy (s-SNOM) to spatially resolve coupling between surface phonon modes. Spatially varying couplings between the longitudinal optical and surface phonon polariton modes of boron nitride nanotubes are observed, and a simple model is proposed.