Terahertz polarization conversion from optical dichroism in a topological Dirac semimetal

Author:

Meng Haiyu12,Wang Lingling3,Lee Ching Hua2,Ang Yee Sin4ORCID

Affiliation:

1. School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411100, China

2. Department of Physics, National University of Singapore, Singapore 117542

3. School of Physics and Electronics, Hunan University, Changsha 410082, China

4. Science, Mathematics and Technology (SMT), Singapore University of Technology and Design, Singapore 497372

Abstract

Topological Dirac semimetals (TDSMs), such as Cd3As2 and Na3Bi, exhibit strong optical dichroism with contrasting dielectric permittivity along different crystal axes. However, such optical dichroism is often overlooked in the study of TDSM-based optoelectronic devices and whether such optical dichroism can lead to unique functionalities not found under the isotropic approximation remains an open question, thus far. Here, we show that the optical dichroism in TDSM lead to starkly different terahertz (THz) responses and device performance as compared to the isotropic case. Using finite-difference time-domain simulations of a Cd3As2-based metasurface, we demonstrate that such optical dichroism can lead to an unexpected THz wave polarization conversion even if the metasurface structure remains fourfold rotationally symmetric, a useful feature not achievable under the isotropic model of TDSM. Our findings concretely reveal the contrasting spectral response between isotropic and anisotropic media and shed important light on the capability of anisotropic TDSM in THz applications, leading not just to the more accurate device modeling but also a new route in realizing THz wave polarization conversion without the need for complex device morphology commonly employed in conventional polarization converters.

Funder

SUTD Start-up Research Grant

National Natural Science Foundation of China

Publisher

AIP Publishing

Subject

Physics and Astronomy (miscellaneous)

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