This study presents advancements in the synthesis and application of Bi2Se3, a topological van der Waals crystal, for terahertz (THz) detection. High-quality β-Bi2Se3 crystals were synthesized using the Selenium Vapor-Induced Supersaturated Solution Method (SVI-SSM), ensuring stoichiometric integrity. Heterostructures of Bi2Se3 were constructed using hot transfer methods, leading to the fabrication of a rectenna THz detector. Utilizing a 0.95-THz injection-seeded THz parametric generator (is-TPG) as the light source for pulsed-continuous wave (CW) THz waves, THz detection experiments were conducted. The results demonstrated a fast response time of 200 ps and a sensitivity of 40 mV/W with the THz detector, which was maintained even under zero bias conditions. These findings lay the foundation for developing passive THz detection systems with minimal energy consufmption, holding significant promise for advancing THz communication technology.
This paper reviews recent advancements in the research of THz detection by an asymmetric dual-grating gate structure epitaxial-graphene-channel field effect transistor (ADGG-EG-FETs). We designed and fabricated ADGG-EGFET for plasmonic (PL) detection, and it performed a high sensitivity and fast response to irradiated THz with 0.95 THz. The behavior of measured dependence on gate bias voltage cannot be explained only by the PL effect. We found such a phenomenon as a new current-driven phototermoelectric (PTE) detection assisted by electrostatic carrier drift/diffusion under the application of DC drain biases. Furthermore, we analyze the response speed of our fabricated detector to reveal the transition point between PL and PTE detection mechanisms. The minimum output pulse width was ~190 ps when one ADGG bias was at the Dirac voltage (i.e., charge neutrality point) to promote the PL detection, whereas the pulse width was ~200 ps when both ADGG biases were at well-doped levels to promote the PTE detection. Compared with the input pulse width of 155 ps, the intrinsic response time of the detector was estimated to be 10 ps for the PL and 20 ps for the PTE detection. This can be quantitatively explained by the characteristic relaxation times of the momentum relaxation for the PL, and the energy relaxation of the hot electrons by optical-phonon emission for the PTE detection. These results indicate that the ADGG-EG-FETs THz detectors are promising for applications in 6G to 7G-class THz wireless communication systems.
This paper reviews recent advances in the terahertz (THz) graphene-based 2D-heterostructure lasers and amplifiers. The linear gapless graphene energy spectrum enables population inversion under optical and electrical pumping giving rise to the negative dynamic conductivity in a wide THz frequency range. We first theoretically discovered these phenomena and recently reported on the experimental observation of the amplified spontaneous THz emission and single-mode THz lasing at 100K in the current-injection pumped graphene-channel field-effect transistors (GFETs) with a distributedfeedback dual-gate structure. We also observed the light amplification of stimulated emission of THz radiation driven by graphene-plasmon instability in the asymmetric dual-grating gate (ADGG) GFETs by using a THz time-domain spectroscopy technique. Integrating the graphene surface plasmon polariton (SPP) oscillator into a current-injection graphene THz laser transistor is the most promising approach towards room-temperature intense THz lasing.
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