Interfaces between two different electron channels (a) or between a channel and conducting plane (b) can act as amplifying mirrors for terahertz plasmons. Field matching at the interface solely by plasmons is impossible due to their different decay lengths.
Dispersion curves for non-drifting and drifting plasmons. Whereas non-drifting plasmons (black lines) have the same dispersion for opposite directions, drifting plasmons (orange lines) propagating in opposite directions have different wavenumbers.
Mode spectrum of a two-dimensional channel at a single frequency (1 THz). The system supports two plasmons propagating in opposite directions with different propagation constants (circles on the horizontal axis) and infinite number of evanescent modes with complex propagation constants (dots merging into continuous lines). There are no waveguide modes due to the small dielectric thickness (w = 100 nm).
Amplitude and power reflection and transmission coefficients of plasmons against the dc current density. The plasmons can be amplified: the amplitude (a) and (d), and the power (b) and (e), coefficients can exceed those in the absence of drift, and the combined power of the reflected and transmitted plasmons (c) and (f), can exceed that of the incident plasmon. Plasmons are incident from the left in (a)–(c) and from the right in (d)–(f).
Distributions of electric and magnetic fields established when a drifting plasmon is incident from the left on a two-channel interface, placed at z = 0. Far from the interface, the distributions show interference between the incident and reflected plasmons and the reflected plasmon. Close to the interface, up to about 100–200 nm, evanescent waves distort the field patterns.
Amplitude and power reflection coefficients of plasmons incident on a conducting plane exceed unity when the drift is directed away from the plane. Amplification is larger for small dc electron density (a) and (b).
Distributions of electric and magnetic fields established when a drifting plasmon is incident on a conducting-plane interface, placed at z = 0. The incident and reflected plasmons form the field patterns away from the interface, while close to it, the evanescent waves play additional role, compare with Fig. 5.
Two-mirror resonators (a), (c), and (e), comprising the amplifying two-channel and conducting-plane interfaces. All of them have roundtrip gain (b), (d), and (f), smaller than unity. Here and in following figures, solid lines denote resonating sections with while dashed lines denote sections with .
The reflection coefficient of plasmon incident from the left on the composite mirror in Fig. 8(e) as a function of the length of the middle, resonating section. Its absolute value of can exceed that of individual interfaces, compare with Figs. 4 and 6.
Three-mirror oscillator comprising two different channels (a) and the complex roundtrip gain of the left (b) and right (c) resonators. The roundtrip gain can have real values exceeding unity.
Article metrics loading...
Full text loading...