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Nanowire-based devices for THz polarimetry - Prof Michael B Johnston
Over the past few decades THz time domain spectroscopy (THz-TDS) has revolutionized spectroscopy and imaging in this rich region of the electromagnetic spectrum.[1] THz-TDS directly measures electric field as a function of time, making it excellent for probing the dielectric properties of materials.[1] The pulsed nature of the technique has allowed it to be extended to study dynamic process with femtosecond time resolution.[2] To date most THz-TDS spectrometers and imagers just generate and measure linearly polarized THz radiation. However, the polarization state of a THz pulse can contain as much information as in the amplitude and phase spectra.[3,4] We have exploited the unique interactions of semiconductor nanowires to optical and THz photons [4] to designed and realize a compact THz detector that measures the complete state of a THz pulse.[5] The detector consists of two orthogonal bow-tie antennas fabricated on an insulating quartz substrate. Each antenna pair is connected by InP nanowires in such a way that the orthogonal antennas are electrically insulated from each other. The polarization selectivity of the nanowires to a gating laser pulse combined with minimal shadowing makes nanowires the ideal photoconductive element in this detector. Using this detector, we have performed THz polarimetry on THz meta-materials and characterized anisotropic media [5]. The design of our detector eliminates cross-talk between polarization channels and the resulting device also very compact and alignment insensitive. Thus, the cross-nanowire detector can easily replace a standard photoconductive emitter in most THz-TDS systems without significant alteration to the spectrometer or imaging system.

[1] SS Dhillon et al. The 2017 terahertz science and technology roadmap.
J. Phys. D-Appl. Phys., 50:043001 (2017)
[2] CQ Xia, S Ponce, JL Peng, AM Ulatowski, JB Patel, AD Wright, RL Milot, H Kraus, QQ Lin, LM Herz, F Giustino, MB Johnston. Ultrafast photo-induced phonon

Jan 20, 2022 11:00 AM in Canberra, Melbourne, Sydney

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