Abstract
Abstract To realize nonreciprocal transmission, it is necessary to break the time-reversal symmetry of the transmission system, but it is very challenging to keep the linear polarized (LP) input and output unchanged in the free space transmission system. Magnetized semiconductor InSb can realize terahertz (THz) nonreciprocal transmission for the two conjugated photonic spin states, but it cannot realize efficient one-way transmission of LP state due to gyro-mirror symmetry. In this work, by introducing a pair of orthogonal uniaxial anisotropies from the meta-gratings on both sides of InSb, both the gyro-mirror and time-reversal symmetries are broken for the LP state, thus making this cascaded grating–InSb–grating structure serves as a high-performance isolator for the LP light. The experiment results indicate isolation of 50 dB at 0.4 THz for the same LP input and output under a weak biased magnetic field of 0.17 T. Moreover, we further illustrate the factors affecting the isolation bandwidth of the device, also demonstrated another broadband structure with the 10 dB isolation bandwidth from 0.2–0.7 THz, and the relative bandwidth achieves 110%. The mechanisms of THz nonreciprocal transmission and polarization manipulation proposed in this work will contribute to the development of efficient THz magneto-optical devices.
Highlights
Isolators and circulators are nonreciprocal one-way transmission devices, in which the forward electromagnetic wave propagates with low insertion losses, but the backward wave cannot transmit due to a very large attenuation [1,2,3], which plays some great important roles in the protection of source and detector, impedance matching, noise-canceling, and decoupling [4, 5]
By introducing a pair of orthogonal uniaxial anisotropies from the meta-gratings on both sides of InSb, both the gyro-mirror and time-reversal symmetries are broken for the linear polarized (LP) state, making this cascaded grating–InSb–grating structure serves as a high-performance isolator for the LP light
By combining the meta-gratings with the gyroelectric semiconductor InSb, we proposed a THz isolator for the LP input to LP output
Summary
Isolators and circulators are nonreciprocal one-way transmission devices, in which the forward electromagnetic wave propagates with low insertion losses, but the backward wave cannot transmit due to a very large attenuation [1,2,3], which plays some great important roles in the protection of source and detector, impedance matching, noise-canceling, and decoupling [4, 5]. Due to the lack of feasible, broadband, and low-loss THz nonreciprocal transmission devices, THz echoes of the reflection and scattering from system components limits the performance of these THz systems It threatens the safety of high-power THz source [10,11,12] and high-sensitive detection systems [13, 14], which is an essential component in these booming systems. THz magneto-optical (MO) materials [15,16,17,18,19] provide a fundamental way of developing nonreciprocal devices It requires significant MO effects in the THz regime operating under a relatively weak external magnetic field (MF) and small absorption loss for THz waves; the materials which meet the above conditions are very rare in the THz regime. Different from the THz spintronic devices controlled by the polarization state of femtosecond laser [11, 12], the polarization state of THz wave passing through InSb can be
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
