11 research outputs found
Plasma instability and amplification of electromagnetic waves in low-dimensional electron systems
A general electrodynamic theory of a grating coupled two dimensional electron
system (2DES) is developed. The 2DES is treated quantum mechanically, the
grating is considered as a periodic system of thin metal strips or as an array
of quantum wires, and the interaction of collective (plasma) excitations in the
system with electromagnetic field is treated within the classical
electrodynamics. It is assumed that a dc current flows in the 2DES. We consider
a propagation of an electromagnetic wave through the structure, and obtain
analytic dependencies of the transmission, reflection, absorption and emission
coefficients on the frequency of light, drift velocity of 2D electrons, and
other physical and geometrical parameters of the system. If the drift velocity
of 2D electrons exceeds a threshold value, a current-driven plasma instability
is developed in the system, and an incident far infrared radiation is
amplified. We show that in the structure with a quantum wire grating the
threshold velocity of the amplification can be essentially reduced, as compared
to the commonly employed metal grating, down to experimentally achievable
values. Physically this is due to a considerable enhancement of the grating
coupler efficiency because of the resonant interaction of plasma modes in the
2DES and in the grating. We show that tunable far infrared emitters, amplifiers
and generators can thus be created at realistic parameters of modern
semiconductor heterostructures.Comment: 28 pages, 15 figures, submitted to Phys. Rev.
Control of absolute negative mobility via noise recycling procedure
Absolute negative mobility (ANM) is investigated in a spatially-periodic symmetric system
under the influence of noise consisting of the superposition of a white Gaussian noise
with the same noise delayed by time τ. The effects of the noise intensity
σ, the time delay τ and feedback intensity
ϵ in the noise recycling are discussed. It is found that the noise
intensity σ and time delay τ can induce the phenomenon
of ANM, while the feedback intensity ϵ can not induce it. This phenomenon
of ANM can be tested in the setup consisting of a resistively and capacitively shunted
Josephson junction device by using a vertical cavity surface emitting laser to generate
the noise recycling procedure