We demonstrate the generation of radially polarized terahertz pulses via optical rectification in a Cherenkov geometry exploiting velocity mismatch, contrary to the traditional approach for generating linearly polarized terahertz beams. A compact system is implemented using 001-cut ZnTe pumped by an ultrafast Yb-doped fiber amplifier.
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http://dx.doi.org/10.1364/ol.32.000433 | DOI Listing |
ACS Appl Mater Interfaces
January 2025
State Key Laboratory of Optoelectronic Materials and Technologies, School of Materials Science and Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China.
Terahertz (THz) emission arising from the second-order nonlinear photocurrent effects in two-dimensional quantum materials has attracted significant attention due to its high efficiency and ease of polarization manipulation. However, in centrosymmetric quantum materials, the terahertz emission is typically suppressed, caused by the directional symmetry of the photocurrent generated under femtosecond laser excitation. In this work, we report that wafer-scale type-II Dirac semimetal PtTe with lattice centrosymmetry exhibits remarkably high THz emission efficiency (2 orders of magnitude greater than that of a ZnTe nonlinear crystal with equivalent thickness) and pronounced polarization sensitivity at room temperature.
View Article and Find Full Text PDFAdv Sci (Weinh)
December 2024
RIKEN Center for Advanced Photonics, RIKEN, 519-1399 Aramaki-Aoba, Sendai, Miyagi, 980-0845, Japan.
This study presents a generalized design strategy for novel terahertz-wave polarization space-division multiplexing meta-devices, functioning as multi-polarization generators, modulators, and analyzers. It introduces the spin-decoupled phase control method by combining gradient phase design with circular polarization multiplexing techniques, enabling exceptional flexibility in controlling the polarization directions and spatial distributions of multiple output beams. The meta-device M-4D is significantly demonstrated as proof of concept, which converts an incident linearly polarized wave into four beams with distinct polarization angles.
View Article and Find Full Text PDFSci Rep
December 2024
Department of Electronics, Carleton University, Ottawa, ON, K1S 5B6, Canada.
In this paper, we propose a novel structure of anisotropic graphene-based hyperbolic metamaterial (AGHMM) sandwiched as a defect between two one-dimensional photonic crystals (PCs) in the terahertz (THz) region. The proposed structure is numerically simulated and analyzed using the transfer matrix method, effective medium theory and three-dimensional finite-difference time-domain. The defect layer of AGHMM consists of graphene sheets separated by subwavelength dielectric spacers.
View Article and Find Full Text PDFBiosensors (Basel)
November 2024
Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
Biosensors operating in the terahertz (THz) region are gaining substantial interest in biomedical analysis due to their significant potential for high-sensitivity trace-amount solution detection. However, progress in compact, high-sensitivity chips and methods for simple, rapid and trace-level measurements is limited by the spatial resolution of THz waves and their strong absorption in polar solvents. In this work, a compact nonlinear optical crystal (NLOC)-based reflective THz biosensor with a few arrays of asymmetrical meta-atoms was developed.
View Article and Find Full Text PDFNano Lett
December 2024
Physics Department, University of Regensburg, 93040 Regensburg, Germany.
Nonlinear electron transport induced by polarized terahertz radiation is studied in two-dimensional tellurene at room temperature. A direct current, quadratic in the radiation's electric field, is observed. Contributions sensitive to radiation helicity and polarization orientation as well as polarization independent current are found.
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