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Terahertz Light Emission and Lasing in Current-Driven Graphene-based 2D Nano- and Plasmonic-Structures

Taiichi Otsuji

Graphene has attracted considerable attention due to its massless and gapless energy spectrum of Dirac Fermions as well as strong light-matter interactions via plasmon-polaritons. This paper highlights recent advances in terahertz (THz) light emission and lasing in current-driven graphenebased 2D nano-structures.The dual-gate graphene channel transistor (DGGFET) structure promotes carrier population inversion in the lateral p-i-n junctions under complementary dual-gate biased and forward drain biased conditions, promoting spontaneous incoherent THz light emission. A laser cavity structure implemented in the active gain area can transcend the incoherent light emission to the single-mode lasing. We designed and fabricated the distributed feedback (DFB) DG-GFET. The GFET channel consists of a double layer (non-Bernal) epitaxial graphene, providing an intrinsic field-effect mobility exceeding 100,000 cm2/Vs. The teeth-brashshaped DG forms the DFB cavity having the fundamental mode at 4.96 THz. THz emission from the sample was measured using a Fouriertransform spectrometer with a 4.2K-cooled Si bolometer. Broadband rather intense (~10 µW) am-plified spontaneous emission from 1 to 7.6 THz and weak (~0.1 µW) single-mode lasing at 5.2 THz were observed at 100K in different samples.