69 research outputs found
Mass-polariton theory of light in dispersive media
We have recently shown that the electromagnetic field in a medium is made of
mass-polariton (MP) quasiparticles, which are quantized coupled states of the
field and an atomic mass density wave (MDW) [Phys. Rev. A 95, 063850 (2017)].
In this work, we generalize the MP theory of light for dispersive media
assuming that absorption and scattering losses are very small. Following our
previous work, we present two different approaches to the theory of light: (1)
the MP quasiparticle theory, which is derived by only using the fundamental
conservation laws and the Lorentz transformation; (2) the classical optoelastic
continuum dynamics (OCD), which is a generalization of the electrodynamics of
continuous media to include the dynamics of the medium under the influence of
optical forces. For the coupled MP state of a single photon and the medium, we
obtain the total MP momentum of the Minkowski form while the field's share of
the momentum is equal to the Abraham momentum. We also show that the
correspondence between the MP and OCD models and the conservation of momentum
at interfaces gives an unambiguous formula for the optical force. The dynamics
of the light pulse and the related MDW lead to nonequilibrium of the medium and
to relaxation of the atomic density by sound waves in the same way as for
nondispersive media. We also carry out simulations for optimal measurements of
atomic displacements related to the MDW in silicon. In the simulations, we
consider different waveguide cross-sections and optical pulse widths and
account for the breakdown threshold irradiance of materials. We also compare
the MP theory to previous theories of the momentum of light in a dispersive
medium. We show that our generalized MP theory resolves all the problems
related to the Abraham-Minkowski dilemma in a dispersive medium
QED based on eight-dimensional spinorial wave equation of the electromagnetic field and the emergence of quantum gravity
Quantum electrodynamics (QED) is the most accurate of all experimentally
verified physical theories. How QED and other theories of fundamental
interactions couple to gravity through special unitary symmetries, on which the
standard model of particle physics is based, is, however, still unknown. Here
we develop a coupling between the electromagnetic field, Dirac
electron-positron field, and the gravitational field based on an
eight-component spinorial representation of the electromagnetic field. Our
spinorial representation is analogous to the well-known representation of
particles in the Dirac theory but it is given in terms of 8x8 bosonic gamma
matrices. In distinction from earlier works on the spinorial representations of
the electromagnetic field, we reformulate QED using eight-component spinors.
This enables us to introduce the generating Lagrangian density of gravity based
on the special unitary symmetry of the eight-dimensional spinor space. The
generating Lagrangian density of gravity plays, in the definition of the gauge
theory of gravity and its symmetric stress-energy-momentum tensor source term,
a similar role as the conventional Lagrangian density of the free Dirac field
plays in the definition of the gauge theory of QED and its electric
four-current density source term. The fundamental consequence, the Yang-Mills
gauge theory of unified gravity, is studied in a separate work
[arXiv:2310.01460], where the theory is also extended to cover the other
fundamental interactions of the standard model. We devote ample space for
details of the eight-spinor QED to provide solid mathematical basis for the
present work and the related work on the Yang-Mills gauge theory of unified
gravity
Noiseless amplification of weak coherent fields without external energy
According to the fundamental laws of quantum optics, noise is necessarily
added to the system when one tries to clone or amplify a quantum state.
However, it has recently been shown that the quantum noise related to the
operation of a linear phase-insensitive amplifier can be avoided when the
requirement of a deterministic operation is relaxed. Nondeterministic noiseless
linear amplifiers are therefore realizable. Usually nondeterministic amplifiers
rely on using single photon sources. We have, in contrast, recently proposed an
amplification scheme in which no external energy is added to the signal, but
the energy required to amplify the signal originates from the stochastic
fluctuations in the field itself. Applying our amplification scheme, we examine
the amplifier gain and the success rate as well as the properties of the output
states after successful and failed amplification processes. We also optimize
the setup to find the maximum success rates in terms of the reflectivities of
the beam splitters used in the setup. In addition, we discuss the nonidealities
related to the operation of our setup and the relation of our setup with the
previous setups.Comment: arXiv admin note: substantial text overlap with arXiv:1309.428
Thermal balance and photon-number quantization in layered structures
The quantization of the electromagnetic field in lossy and dispersive
dielectric media has been widely studied during the last few decades. However,
several aspects of energy transfer and its relation to consistently defining
position-dependent ladder operators for the electromagnetic field in
nonequilibrium conditions have partly escaped the attention. In this work we
define the position-dependent ladder operators and an effective local
photon-number operator that are consistent with the canonical commutation
relations and use these concepts to describe the energy transfer and thermal
balance in layered geometries. This approach results in a position-dependent
photon-number concept that is simple and consistent with classical energy
conservation arguments. The operators are formed by first calculating the
vector potential operator using Green's function formalism and Langevin noise
source operators related to the medium and its temperature, and then defining
the corresponding position-dependent annihilation operator that is required to
satisfy the canonical commutation relations in arbitrary geometry. Our results
suggest that the effective photon number associated with the electric field is
generally position dependent and enables a straightforward method to calculate
the energy transfer rate between the field and the local medium. In particular,
our results predict that the effective photon number in a vacuum cavity formed
between two lossy material layers can oscillate as a function of the position
suggesting that also the local field temperature oscillates. These oscillations
are expected to be directly observable using relatively straightforward
experimental setups in which the field-matter interaction is dominated by the
coupling to the electric field
Generalized noise terms for the quantized fluctuational electrodynamics
The quantization of optical fields in vacuum has been known for decades, but
extending the field quantization to lossy and dispersive media in
nonequilibrium conditions has proven to be complicated due to the
position-dependent electric and magnetic responses of the media. In fact,
consistent position-dependent quantum models for the photon number in resonant
structures have only been formulated very recently and only for dielectric
media. Here we present a general position-dependent quantized fluctuational
electrodynamics (QFED) formalism that extends the consistent field quantization
to describe the photon number also in the presence of magnetic field-matter
interactions. It is shown that the magnetic fluctuations provide an additional
degree of freedom in media where the magnetic coupling to the field is
prominent. Therefore, the field quantization requires an additional independent
noise operator that is commuting with the conventional bosonic noise operator
describing the polarization current fluctuations in dielectric media. In
addition to allowing the detailed description of field fluctuations, our
methods provide practical tools for modeling optical energy transfer and the
formation of thermal balance in general dielectric and magnetic nanodevices. We
use the QFED to investigate the magnetic properties of microcavity systems to
demonstrate an example geometry in which it is possible to probe fields arising
from the electric and magnetic source terms. We show that, as a consequence of
the magnetic Purcell effect, the tuning of the position of an emitter layer
placed inside a vacuum cavity can make the emissivity of a magnetic emitter to
exceed the emissivity of a corresponding electric emitter
Monte Carlo study of non-quasiequilibrium carrier dynamics in IIIâN LEDs
Hot carrier effects have been observed in recent measurements of IIIâNitride (IIIâN) light-emitting diodes. In this paper we carry out bipolar Monte Carlo simulations for electrons and holes in a typical IIIâN multi-quantum well (MQW) LED. According to our simulations, significant non-quasiequilibrium carrier distributions exist in the barrier layers of the structure. This is observed as average carrier energies much larger than the 1.5kBT1.5kBT corresponding to quasi-equilibrium. Due to the small potential drop over the MQW being modest, the non-quasiequilibrium carriers can be predominantly ascribed to nnp and npp Auger processes taking place in the QWs. Further investigations are needed to determine the effects of hot carriers on the macroscopic device characteristics of real devices
Photon momentum and optical forces in cavities
During the past century, the electromagnetic field momentum in material media
has been under debate in the Abraham-Minkowski controversy as convincing
arguments have been advanced in favor of both the Abraham and Minkowski forms
of photon momentum. Here we study the photon momentum and optical forces in
cavity structures in the cases of dynamical and steady-state fields. In the
description of the single-photon transmission process, we use a field-kinetic
one-photon theory. Our model suggests that in the medium photons couple with
the induced atomic dipoles forming polariton quasiparticles with the Minkowski
form momentum. The Abraham momentum can be associated to the electromagnetic
field part of the coupled polariton state. The polariton with the Minkowski
momentum is shown to obey the uniform center of mass of energy motion that has
previously been interpreted to support only the Abraham momentum. When
describing the steady-state nonequilibrium field distributions we use the
recently developed quantized fluctuational electrodynamics (QFED) formalism.
While allowing detailed studies of light propagation and quantum field
fluctuations in interfering structures, our methods also provide practical
tools for modeling optical energy transfer and the formation of thermal balance
in nanodevices as well as studying electromagnetic forces in optomechanical
devices
Bipolar Monte Carlo Simulation of Hot Carriers In III-N LEDs
We carry out bipolar Monte Carlo (MC) simulations of electron and hole transport in a multi-quantum well light-emitting diode with an electron-blocking layer. The MC simulation accounts for the most important interband recombination and intraband scattering processes and solves self-consistently for the non-quasiequilibrium transport. The fully bipolar MC simulator results in better convergence than our previous Monte Carlo-drift-diffusion (MCDD) model and also shows clear signatures of hot holes. Accounting for both hot electron and hot hole effects increases the total current and decreases the efficiency especially at high bias voltages. We also present our in-house full band structure calculations for GaN to be coupled later with the MC simulation in order to enable even more detailed predictions of device operation
Cooling of radiative quantum-dot excitons by terahertz radiation: A spin-resolved Monte Carlo carrier dynamics model
We have developed a theoretical model to analyze the anomalous cooling of
radiative quantum dot (QD) excitons by THz radiation reported by Yusa et al
[Proc. 24th ICPS, 1083 (1998)]. We have made three-dimensional (3D) modeling of
the strain and the piezoelectric field and calculated the 3D density of states
of strain induced quantum dots. On the basis of this analysis we have developed
a spin dependent Monte Carlo model, which describes the carrier dynamics in
QD's when the intraband relaxation is modulated by THz radiation. We show that
THz radiation causes resonance transfer of holes from dark to radiative states
in strain-induced QD's. The transition includes a spatial transfer of holes
from the piezoelectric potential mimima to the deformation potential minimum.
This phenomenon strongly enhances the QD ground state luminescence at the
expense of the luminescence from higher states. Our model also reproduces the
delayed flash of QD ground state luminescence, activated by THz radiation even
s after the carrier generation. Our simulations suggest a more general
possibility to cool the radiative exciton subsystem in optoelectronic devices.Comment: 18 pages, 1 table, 8 figures, submitted to Physical Review B v2:
major conceptual changes. The article was extended considerably to suit
Physical Review B (instead of Physical Review Letters
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