Amplifying mirrors for terahertz plasmons

Abstract

Semiconductor plasmons have long held out a promise for terahertz generation, but competitive plasmonic mechanisms have yet to be found. Here, we introduce amplifying terahertz mirrors: planar interfaces for two-dimensional electron channels that amplify plasmons in the presence of electron drift. In contrast to existing formulations, we develop a rigorous mode matching technique that takes the complete mode spectrum into account. Mirrors are characterized by plasmon reflection and transmission coefficients whose values can increase with drift. Amplitude and power coefficients are determined, and conditions are found for their values to exceed unity. Resonators based on different combinations of amplifying mirrors are investigated, and an asymmetric configuration (consisting of two different electron channels confined between conducting planes) whose roundtrip gain can exceed unity is identified. The unusual conditions needed for oscillation are examined in detail and the general advantages of asymmetric arrangements are highlighted. Finally, the potential of mode matching as a universal tool for plasmonics is discussed.

Amplified-reflection plasmon instabilities in grating-gate plasmonic crystals

“…Our mechanism of instability can be understood as follows. In a single gated cell of plasmonic crystal, the downstream plasmon undergoes an amplified DyakonovShur reflection from the gated/ungated boundary 21,22 . In an isolated gated cell, the reflected upstream wave would be attenuated upon reflection from the opposite boundary.…”

Amplification and generation of terahertz plasmons in gated two-dimensional channels: Modal analysis

“…Some studies have indeed taken all four of them into account. 7,14 However, as numerical calculations show, 14 amplification upon reflection can be explained solely by an interplay of the low-wavenumber plasmons. v 0 ¼ 3 Â 10 6 cm/s.…”

“…In contrast, previous papers considered either open channels 15,16 or channels closed on both sides. 13,14 Section II introduces the model. Section III considers reflection from a conducting boundary (a source or a drain) and demonstrates plasmon amplification.…”

“…Solving Maxwell's equations and using the Fourier analysis and, Popov et al 12 studied plasmon generation and coupling to electromagnetic radiation in one-dimensional FET arrays. Sydoruk et al 13,14 developed a semi-analytical model based on mode matching. The latter, in contrast to the traditional treatment of Dyakonov and Shur, relies on electrodynamic boundary conditions and takes into account the field distributions along an entire contact.…”

“…The latter, in contrast to the traditional treatment of Dyakonov and Shur, relies on electrodynamic boundary conditions and takes into account the field distributions along an entire contact. It has been used to predict distributed gain in channels with multiple sections, 13 to study plasmon amplification at contacts, 14,15 and to consider effects of electron collisions and diffusion. 16 This paper develops further the mode-matching technique for plasmon amplification.…”