We present a theoretical study of the transverse and longitudinal parts of the evanescent electric field from a current density sheet (quantum well). The aim is to identify the part of the evanescent field which upon quantization belongs to the transverse photons. An examination of the field momentum shows that the transverse field is prevented from escaping the evanescent tail by its coupling to the longitudinal field momentum attached to the sheet particles. In the perspective of the four-potential the field-matter interaction is spread over the entire evanescent regime, and in QED this corresponds to an interaction between transverse photons and longitudinal and scalar photons.
A unified description of the physics of the photon based on the transverse vector potential is presented. The description covers subjects from microscopic quantum electrodynamics (QED) to eikonal theory in curved space-time. The link between photon wave mechanics and QED is emphasized. Localized transverse single-photon states in direct space are introduced via a new mean position state in Hilbert space. It is shown that the related correlation matrix is proportional to the transverse subspace part of the Feynman photon propagator. It is argued that a transverse photon acquires an effective rest mass in its interaction with charged massive particles. Starting from the Lorenz gauge four-potential form of the Maxwell-Lorentz equations in General Relativity, the eikonal theory for transverse (unlocalized) light particles is discussed. Contact to the geodesic equation for light rays is made.
Proc. SPIE. 7355, Photon Counting Applications, Quantum Optics, and Quantum Information Transfer and Processing II
KEYWORDS: Particles, Free space, Near field, Quantum electrodynamics, Geometrical optics, Space operations, Electromagnetism, Electrodynamics, Wave mechanics, Near field optics
When rewritten in an appropriate manner, the microscopic Maxwell-Lorentz equations appear as a wave-mechanical
theory for photons, and their quantum physical interaction with matter. A natural extension leads
from photon wave mechanics to quantum electrodynamics (QED). In its modern formulation photon wave mechanics
has given us valuable new insight in subjects such as spatial photon localization, near-field photon
dynamics, transverse photon mass, photon eikonal theory, photon tunneling, and rim-zone electrodynamics. The
present review is based on my plenary lecture at the SPIE-Europe 2009 Optics and Optoelectronics International
Symposium in Prague.
Quantum physical aspects of near-field optics are discussed on the basis of photon wave mechanics, and the upgraduation of the present transverse propagator formalism to the field-theoretic level described.
Optical properties of ultrathin aluminum quantum wells deposited on glass (SiO_{2}) and crystalline silicon (a-Si) are studied at room temperature in the infrared region at 9.201 micrometers wavelength within two thicknesses range: d approximately 5 to 35 angstroms and 36 to 112 angstroms. All our thickness dependence reflectivity measurements were made by tuning a CO_{2} laser to 9.201 micrometers for p-polarization and an angle of incidence of 7 degree(s). Our main contribution here is the reveled fine oscillatory behavior on a gradually increasing reflectivity spectra. These fine oscillation structure can be attributed to quantum size effects.
Experimental and theoretical investigations of the optical second-harmonic generation (SHG) from ultrathin niobium films embedded in a dielectric are presented. The dependence of the intensity of second-harmonic emission on the film thickness (in the range from 6 to 42 angstroms) and the angular dependencies of SHG are investigated for different polarization configurations. The thickness dependencies of the second-harmonic intensity reveal resonant behavior: the p_{(omega} )-to-p_{2(omega} ) second-harmonic intensity exhibits a pronounced maximum for a film thickness of approximately 15 angstroms while the s_{(omega} )-to-p_{2(omega} ) second-harmonic signal exhibits a step-like increase at the same thickness. By modeling the metal film as a symmetric quantum well, a microscopic local-field calculation of the second-harmonic generation is performed, and numerical results for the thickness and angular dependencies of the second-harmonic energy reflection coefficient are presented. Using simply infinite-barrier wave functions together with a self-field approximation the theoretical calculations qualitatively describe the observed thickness dependence of the second-harmonic generation which can be accounted for by the intersubband transitions in the quantum wells formed by the niobium films.
A microscopic local-field calculation of the infrared second-harmonic generation associated with intersubband transitions in a single GaAs/AlGaAs quantum-well structure subjected to an applied electric field is presented. Taking as a starting point a fundamental selfconsistent integral equation for the local field, the p-polarized first-harmonic fields inside the quantum well are calculated exactly. The result for the local-field calculation at the first-harmonic frequency is used to calculate the p-polarized second-harmonic local field. The conversion efficiency of the second-harmonic generation from the quantum well is determined. Numerical calculations of the frequency spectra of the second-harmonic powers are presented for different applied fields. The numerical results show that strong second-harmonic generation occurs in the vicinity of the resonance frequencies for the first- and second-harmonic local field inside the quantum well. The influence of the applied field on the optical second- harmonic generation is investigated. It is demonstrated that the presence of the dc bias leads to a blue-shift of the resonance frequencies in the SH energy reflection spectra stemming from the quantum-confined Stark effect, and that the maximum value of the SH power decreases when the applied field is increased.
The interband and intersubband transitions in amorphous Si/SiO_{2} multiple quantum well structures, nonlinear effects, and relations between nonlinearity and electron recombination channels have been investigated. Three types of radiative transitions have been observed: subband-to-subband recombination, recombination between subbands of the well and the impurity states in the barrier layers, and the recombination related to impurity states in the barrier layers. A relaxation of excited carriers between the subbands within the conduction and valence bands has been found that allows one to observe hot luminescence caused by higher subbands of the quantum well. The dependencies of the luminescence intensity on the excitation intensity show that the recombination rate is dependent on the concentration of excited carriers. Intersubband absorption has been observed for the first time in undoped amorphous multiple quantum well structures under interband excitation. The transitions take place between the first and second subband of the conduction band involving nonequilibrium electrons excited in the first subband with optical pumping. The dispersive nonlinearity has been investigated in the Fabry-Perot formed by the top interface of the structure and the substrate. The refractive index changes obtained from intensity dependent reflection spectra depend on the excitation intensity in nonlinear manner and can be described by the model of saturating nonlinearity for lower pump intensity. The nonlinear refractive index reveals resonant behavior associated with the subband structure of the QWs.
The optical anisotropy of GdBa2Cu3O7-x epitaxial films has been experimentally investigated by use of ellipsometry and polarized reflectance measurements. The individual principal components of the dielectric tensor of this new high-Tc compound are derived from ellipsometric measurements performed in the visible and infrared frequency regions. Our results show that this compound is highly anisotropic in the near infrared region, and that it exhibits strongly free-electron-like behavior in the c-axis direction at optical frequencies.
The stationary energy current density associated with the transmission of light through a metal-vacuum surface
is analysed. Combining the Maxwell equations and Boltzmann's transport equation, a generalized Poynting vector
of the coupled system of light and conduction electrons is obtained. Within the framework of nonlocal optics, the
structure of the electromagnetic and material parts of the Poynting vector is investigated. Dividing the electric
field into divergence-free (T) and rotational-free (L) parts, explicit expressions are derived for the o-ca1led TT and
TL-parts of the electromagnetic Poynting vector, and for the TT, TL, and LL-parts of the Poynting vector associated
with the kinetic energy flow in the electron system. Analytical expressions are derived for the third rank nonlinear
response tensor describing the kinetic energy flow for oblique incident light. Special emphasis is devoted to a study
of the contributions to the energy current density from collective plasmon and polariton excitations in the frequency
range between the longitudinal and transverse plasma edges. A comparison of the present work with previous ones
based on the so-called hydrodynamic description is given.
The integral equation formalism previously used by the present authors to describe scattering of monochromatic
light from a few atomic dipoles on a flat metal surface is used to investigate the properties of the electric field on the
sites of the dipoles. By treating the light-induced radiation from an atom in the electric dipole approximation a set
of linear equations which allows us to determine the electric field on the atomic sites selfconsistently is established.
The contributions to the selfconsistent field from radiative and nonradiative modes and from the excitation of surface
polaritons are described. In the final chapter of our paper a number of numerical results for the case where the
incident electric field is p-polarized are presented. Using dielectric data for Al a detailed analysis of the frequency
dependence of the electric field on the site of one of the dipoles is undertaken.
In connection with a recently obtained quantum mechanical expression for the optical second-harmonic response
tensor (OSHRT) for a BCS-like superconductor, we present a Taylor series expansion of the OSHRT to lowest order
in the wave vector of the fundamental electromagnetic wave. It is shown that in the limit T > Tc , the Taylor
series expansion of the OSHRT is identical to that obtained in the collisionless limit from the Boltzmann equation
approach in the near-local regime. The dispersion relation for waves at the fundamental frequency is obtained using
a Taylor series expansion of the linear conductivity tensor. Numerical results are presented showing the frequency
dependence for parts of the obtained near-local OSHRT involving transversely polarized fundamental waves. In the
superconducting state an increase in the OSHRT in comparison to that in the normal state is found for frequencies
above the gap frequency. Below the gap the OSHRT is smaller in the superconducting phase than in the normal
phase.
This paper describes a joint study of the structure and nonlinear optical properties of vacuum evaporated thin films of copper phthalocyanine (CuPc for brevity). Film thickness ranes from 50 to 500 nm. The anisotropic paramagnetic resonance of Cu ions reveals that the Pc rings lie almost parallel to the substrate plane with however a large angular distribution (300 FWHM). Third harmonic optical generation measurements performed at 1. 064 im and 1. 907 .tmfundamenta1 velengths give respectivel2 an average value of the cubic susceptibility = (4 0. 4) • 10 e. s. u. and (2. 1± O.2)• 1O e.s.u. These values, although significantly higher than for a common ionic crystal, are about one order of magnitude lower than in conjugated 1-D systems, which shows that the 2-D u-electron delocalization is less profitable than the l-D one. Besides third harmonic, we have also observed second harmonic generation. Its polarization dependence is characteristic of a quadratic susceptibility enhanced in one direction, almost pependicular to the substrate, with d 2 1O e.s.u. The possible origins eff of d are discussed. eff