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2013-12-26

A group of researchers at Osaka University and Aisin Seiki Co., Ltd. have developed technology for producing controlled polarization of THz electromagnetic radiation with variations in the creation and arrangement of evenly-spaced stacked metal plates.
As an effective method of material analysis and non-destructive inspection, transmissivity of electromagnetic waves in far-infrared range is attracting attention. It is relatively easy to control light waves in the infrared region; however, there are few technologies for controlling polarization. In order to control polarization without changing the optical axes, phase plates are used. Phase plates made from crystal, plastic, and semiconductors are used in visible near-infrared regions, but there have been no materials functioning as phase plates in middle and far infrared regions.
This group fabricated metal plates with a periodic array of holes created by chemical etching in order to optimize phase variation in the THz frequency range and demonstrated that the phase plates controlled polarization in the frequency region of 0.67 - 1.21 THz.
This group succeeded in creating inexpensive optical devices composed of stacked parallel metal plates by making use of waveguide technology in the THz frequency regions. This technology will contribute in the development of optical isolators and highly-sensitive THz-wave detection.

Graduate School of Engineering Science, Osaka University: Masaya NAGAI, Noriyuki MUKAI, Yosuke MINOWA, Masaaki ASHIDA

Aisin Seiki Co., Ltd.: Jun TAKAYANAGI, Hideyuki OHTAKE

Abstract

We propose a simple achromatic terahertz wave plate composed of stacked parallel metal plates with a hole array. It consists of an ensemble of designed parallel plate waveguides; the high and low propagation speeds of waves in TE and TM waveguide modes with the same group velocity cause a constant phase difference over a wide frequency region. Using that wave plate, we obtained intense single- and multi-cycle THz pulses with circular polarization.

 

Figure 1

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To learn more about this research, please read the full research report entitled "Achromatic THz wave plate composed of stacked parallel metal plates" at this page of the Optics Letters website.



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