Optical Frequency Range Research Articles

Back Cover: Broadband light source using modulated quantum dot structures with sandwiched sub‐nano separator (SSNS) technique (Phys. Status Solidi C 8/2)

In their article on pp. 328ff., Naokatsu Yamamoto et al. describe the development of ultra-broadband light sources using a modulated quantum dot (QD) optical gain material with a sandwich sub-nano separator (SSNS) technique. The cover picture shows a high-quality and high-density InAs/InGaAs QD structure obtained using the novel crystal growth technique, which controls the surface conditions by the SSNS structure. An ultra-broadband (optical frequency range: >14.4 THz bandwidth) and bright (few tenths of mW) light emission in a wavelength range of around 1.2–1.3 µm is successfully demonstrated from the ultra-broadband QD laser diode with the SSNS technique.

Special Section Guest Editorial: Metamaterials: Fundamentals and Applications

Metamaterials have attracted a lot of attention over the last decade 1 and are destined to be the generic basis of applications in many areas of life. They are artificial composites and can be constructed in a variety of ways using some forms of artificial atoms and molecules, which can be termed metaparticles. In the beginning, the emphasis was on microwaves, and a metaparticle consisted of a metal wire combined with a metal split ring. If such metaparticles are arranged at a distance apart greater than their size, then the emergent bulk metamaterial is an average, effective medium that can display a negative permittivity and acquire magnetic properties that have a negative permeability. It is recognised now that many combinations of these negative properties can be created and this beautiful combination of electric and magnetic properties has stimulated a vast global interest. 2,3 Indeed, there is now a major effort to create materials suitable for the optical frequency range and there is, therefore, a major interest in all aspects of how to deploy nanoparticles, for metamaterial purposes, as opposed to wires and split rings. The latter could be scaled down with considerable care and effort but, in general, many new metamaterials will be collections of nanoparticle dispersions, leading to fascinating, collective, average behaviour. In this context, SPIE hosts the Optics and Photonics conference each year in San Diego, California. Considered the largest international meeting of its type in North America, it contains a significant number of constituent conferences on nanoscience and nanoengineering. It is a pleasure to present some pivotal papers from these conferences devoted to metamaterials and metallic nanostructures here as a special section to this journal.

DIRECTIONAL AND POLARIZATION PROPERTIES OF A PLASMONIC CROSS NANOANTENNA

The response of dipole nanoantennas (DNAs) studied widely in optical frequency range is sensitive to polarization of incident field. In this paper, we report the implementation of a cross nanoantenna (CNA) consisting of two orthogonal DNAs with a common feedgap and investigate its directional and polarization properties and compare them with those of the DNA. Interestingly the response of CNA is independent of polarization. We can operate the CNA in turnstile mode by using two identical light sources with cross polarization in phase quadrature. In such a case the radiation from the CNA is found omnidirectional like radio frequency turnstile antenna. We believe CNA could open new possibilities to study the novel phenomenon of light matter interaction. To the best of our knowledge, this is the first report on a turnstile antenna in optical frequencies.

Magnetic field concentrator for probing optical magnetic metamaterials

Development of all dielectric and plasmonic metamaterials with a tunable optical frequency magnetic response creates a need for new inspection techniques. We propose a method of measuring magnetic responses of such metamaterials within a wide range of optical frequencies with a single probe. A tapered fiber probe with a radially corrugated metal coating concentrates azimuthally polarized light in the near-field into a subwavelength spot the longitudinal magnetic field component which is much stronger than the perpendicular electric one. The active probe may be used in a future scanning near-field magnetic microscope for studies of magnetic responses of subwavelength elementary cells of metamaterials.

Compact Metallo-Dielectric Optical Antenna for Ultra Directional and Enhanced Radiative Emission

We report the design of highly efficient optical antennas employing a judicious synthesis of metallic and dielectric materials. In the proposed scheme, a pair of metallic coupled nanoparticles permits large enhancements in both excitation strength and radiative decay rates, while a high refractive index dielectric microsphere is employed to efficiently collect light without spoiling the emitter quantum efficiency. Our simulations indicate potential fluorescence rate enhancements of 3 orders of magnitude over the entire optical frequency range.

Multifrequency parallelized near-field optical imaging with anistropic metal-dielectric stacks

Metal-dielectric stacks can be designed to support resonant transmission modes for certain evanescent field components of an incident electromagnetic field. Here we show that when combined with an appropriate subwavelength pitch grating the amplified Fourier components coincide with different diffraction orders at different frequencies. It thereby becomes possible to collect a wide range of evanescent Fourier components by performing measurements at different optical frequencies. For a typical anisotropic metal-dielectric stack, we find that for a source emitting at wavelengths $400$--$500$ nm, imaging with a resolution of $\ensuremath{\approx}20$ nm becomes possible. Although the reconstructed image contains ringing effects due to gaps in the measured Fourier spectrum, the final resolution achievable is a significant improvement over other fast near-field imaging techniques. The presented technique may find applications in fast super-resolution surface imaging of objects that emit over a wider optical frequency range.

Bohr Correspondence Principle and Multiphoton Nature Raleigh Light Scattering

The correspondence principle and the condition of supplementation were introduced by N. Bohr for the sub-mission of light phenomena, taking into account the wave nature of electromagnetic radiation on one hand, and its quantum structures on the other. In this paper, correspondence principle combines two models of matter, namely, the classical point of view of environment can be considered as an ensemble no equally-frequencies oscillators, i.e. electrons in the surrounding various atoms (molecules) of the matter and characterized by its own set of frequencies (but not hesitant in the absence of an energy source) and the quantum - environment could be presented as a set (ensemble) two-level systems, a wide range of Bohr fre-quencies. According to the correspondence principle Bohr jump-frequencies of atoms (molecules or nano particles) and natural frequencies oscillations of electrons of the same environment - oscillators are equal to each other. The dispersion characteristics of the environment in the every study range of optical frequencies correspond to the model of the classical harmonic oscillator of Lorenz, capable oscillates with Bohr fre-quency. Using the laws of classical mechanics to describe the environment and its dispersion properties, and the simultaneous presentation of light radiation in the form of a beam interacting with the environment of photons (quanta, corpuscles) helps explain peculiarities of the spectral composition Raleigh light scattered.

10.1007/s11487-008-2001-7

A review of the properties of photonic crystals is presented. Possible applications (ICs and electronic devices (amplifiers and oscillators) of the optical frequency range) are outlined. Special attention is paid to crystals with unconventional quasi-optical properties. Crystals that allow so-called backward waves are considered.

Bioresonance therapy with children suffering from allergies—An overview about clinical reports

In 1976, Morell and Rasche, the inventors of the classical bioresonance therapy (e.g. MORA, BICOM, IMEDIS, HOLIMED), postulated a weak, low-frequency electromagnetic field (1–105 Hz) in a human organism that was considered to induce important regulative functions. It is historically interesting that at the same time Popp and Ruth rediscovered the biophotons, an electromagnetic regulation field in the optical frequency range. In the endogenous form of bioresonance the postulated oscillations are picked up by means of hand and foot electrodes and after an electronic inversion they are transmitted back to the body for therapeutic purposes. Within the exogenous form, the postulated oscillations of bio-active substances are transmitted after an electronic inversion (e.g. allergens) or amplification (e.g. nosodes) for therapeutic purposes in the human organism. For about 30 years the exogenous bioresonance therapy has been used for therapy with children all over the world who were suffering from allergic diseases (e.g. bronchial asthma, allergic rhinitis, eczema). As a summary and for the evaluation of clinical results in bioresonance therapy reports we have the following literature available: nine non-controlled and five controlled clinical studies, which give clear evidence of the clinical effectiveness in allergy therapy with children. These trials were carried out by physicians and scientists in universities, hospitals and medical practices all over the world. The nine non-controlled (1050 patients) and three controlled studies (537 patients) are unrestrictedly positive according to the author's report. Two controlled studies (74 patients) had been evaluated negative according to the author's conclusion. However, even in these reports there is some evidence of the clinical effectiveness of bioresonance therapy. Particularly remarkable in the results is the clear and strong dependence of the effectiveness with respect to the age of the probands in the trials. The younger the probands, the higher the effectiveness of bioresonance therapy. In each trial no side effects were observed. The greater majority of the performing scientists and physicians believe – on the basis of their investigations – that the classical bioresonance therapy is clinically effective in allergy therapy for children.

Ab-initio study of the structural, linear and nonlinear optical properties of CdAl 2Se 4 defect-chalcopyrite

The complex density functional theory (DFT) calculations of structural, electronic, linear and nonlinear optical properties for the defect chalcopyrite CdAl 2Se 4 compound have been reported using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the WIEN2k code. We employed the Wu and Cohen generalized gradient approximation (GGA-WC), which is based on exchange–correlation energy optimization to calculate the total energy. Also we have used the Engel–Vosko GGA formalism, which optimizes the corresponding potential for band structure, density of states and the spectral features of the linear and nonlinear optical properties. This compound has a wide direct energy band gap of about 2.927 eV with both the valence band maximum and conduction band minimum located at the center of the Brillouin zone. The ground state quantities such as lattice parameters ( a, c, x, y and z), bulk modulus B and its pressure derivative B′ are evaluated. We have calculated the frequency-dependent complex ε ( ω ) , its zero-frequency limit ε 1 ( 0 ) , refractive index n ( ω ) , birefringence Δ n ( ω ) , the reflectivity R ( ω ) and electron energy loss function L ( ω ) . Calculations are reported for the frequency-dependent complex second-order nonlinear optical susceptibilities. We find opposite signs of the contributions of the 2 ω and 1 ω inter/intra-band to the imaginary part for the dominant component through the wide optical frequency range.

Electromagnetic fields and modal excitations on a thin silver film

In this paper we extend the fast-all-modes method and the numerical modified steepest-descent-path method to the optical frequency range by finding all modes and solving the total electric field in three dimensions that is due to a point source above a lossy thin metal film with a negative permittivity situated between two dissimilar dielectric materials. We show that up to four proper surface wave modes may propagate on the film surface, including both backward and forward waves. We also solve for the electric field below the lossy thin metal film and verify the existence of superlensing of the electric field, comparing that case to the case of a dielectric film where no superlensing occurs. The CPU time using the fast-all-modes method and the numerical modified steepest-descent-path method is considerably less than that using the conventional method of integration along the Sommerfeld integration path.

A modular implementation of dispersive materials for time-domain simulations with application to gold nanospheres at optical frequencies

The development of photonic nano-structures can strongly benefit from full-field electromagnetic (EM) simulations. To this end, geometrical flexibility and accurate material modelling are crucial requirements set on the simulation method. This paper introduces a modular implementation of dispersive materials for time-domain EM simulations with focus on the Finite-Volume Time-Domain (FVTD) method. The proposed treatment can handle electric and magnetic dispersive materials exhibiting multi-pole Debye, Lorentz and Drude models, which can be mixed and combined without restrictions. The presented technique is verified in several illustrative examples, where the backscattering from dispersive spheres is calculated. The amount of flexibility and freedom gained from the proposed implementation will be demonstrated in the challenging simulation of the plasmonic resonance behavior of two gold nanospheres coupled in close proximity, where the dispersive characteristic of gold is approximated by realistic values in the optical frequency range.

Amplification of electromagnetic field in the course of the nonrelativistic electron scattering by ion in the presence of the field of the medium-intensity elliptically polarized light wave

The amplification factor of the electromagnetic field is theoretically studied for the scattering of nonrelativistic electrons by ions in the presence of the field of the elliptically polarized electromagnetic wave. A simple analytical formula for the gain is derived for the medium-intensity range. The formula supplements and extends the domain of applicability of the known Marcuse formula for the linear polarization in the presence of a weak field. It is demonstrated that the maximum gain is reached when the initial electron velocities belong to the polarization plane of the electromagnetic wave. In the range of optical frequencies, the amplification factor of the laser radiation can be significant for relatively high powers of electron beams.

Investigation of a slot nanoantenna in optical frequency range

Following the analogy of radio frequency slot antenna and its complementary dipole, we propose the implementation of a slot nanoantenna (SNA) in the optical frequency range. Using finite-difference time-domain (FDTD) method, we investigate the electromagnetic (EM) properties of a SNA formed in a thin gold film and compare the results with the properties of a gold dipole nanoantenna (DNA) of the same dimension as the slot. It is found that the response of the SNA is very similar to the DNA, like their counterparts in the radio frequency (RF) range. The SNA can enhance the near field intensity of incident field which strongly depends on its feedgap dimension. The resonance of the SNA is influenced by its slot length; for the increasing slot length, resonant frequency decreases whereas the sharpness of resonance increases. Besides, the resonance of the SNA is found sensitive to the thickness of metal film, when the latter is smaller than the skin depth. The effect of polarization of incident field on the EM response of the SNA was examined; the field enhancement is optimum when polarization is parallel to the feedgap. Finally, we calculate the radiation patterns of the DNA and SNA and compare them with those of the RF dipole antenna. The radiation pattern of the SNA is found to be independent of its slot length when excited at resonant frequency. To the best of our knowledge, this is the first study on a slot antenna in the optical frequency.

Equivalent Circuits and Nanoplasmonics

We show how a circuit analysis, used widely in electrical engineering, finds application to problems of light wave injection and transport in subwavelength structures in the optical frequency range. Lumped circuit and transmission-line analysis may prove helpful in the design of plasmonic devices with standard, functional properties.

Nanoelectromagnetics: Circuit and Electromagnetic Properties of Carbon Nanotubes

This Review presents a discussion of the electromagnetic properties of nanoscale electrical conductors, which are quantum mechanical one-dimensional systems. Of these, carbon nanotubes are the most technologically advanced example, and are discussed mainly in this paper. The properties of such systems as transmission electron microscopy waveguides for on-chip signal propagation and also the radiation properties of such systems are discussed. This work is primarily aimed at microwave, nanometer-wave, and THz electronics. However, the use of nanotubes as antennas in the IR and optical frequency range is not precluded on first principles and remains an open research area.

Correlation effects of multiple charged accelerated ions in Cherenkov radiation

The correlation effects in Cherenkov radiation associated with fluctuations of multiple charged accelerated ions in the medium are considered. The contribution of additional correlation into the radiation is determined by the ion charge mean-square deviation from its equilibrium value and defines the non-zero radiation yield as the threshold conditions are not fulfilled. The numerical estimations of the yield of Au ion radiation in the optical and X-ray frequency range in carbon are presented.

A density functional study of second-order susceptibilities in calcium samarium oxyborate Ca4SmO(BO3)3

We report calculations of the linear and nonlinear optical susceptibilities (second harmonic generation) for calcium samarium oxyborate Ca4SmO(BO3)3 using the full-potential linear augmented plane wave method. Our calculations show that this compound is metallic-like with density of states at the Fermi energy EF, N(EF) = 421.6 states/Ry-cell or a bare electronic specific heat coefficient of 73.14 mJ mole−1 K−2. We find that the metallic behaviour is due to the strong overlap of the Sm and O states around EF. We have performed calculations for the two contributions to ε(ω), namely, intra-band and inter-band transitions. The effect of the intra-band term is significant for energies less than 1 eV. We have calculated the various components of the second-order susceptibility tensor and find that is the dominant component. We find opposite signs for the contributions of 2ω and 1ω inter-/intra-band to the real and imaginary parts of the dominant component throughout the wide optical frequency range.

Analytical circuit model for split ring resonators in the far infrared and optical frequency range

The article proposes an LC-circuit model for single split ring resonators (SRRs) operating at far infrared and optical frequencies. Taking the effects of magnetic and kinetic inductances as well as gap and surface capacitances into account, we obtain analytical expressions for the resonant frequency of the singly, doubly, and quadruply split SRRs. Comparing the analytical results with numerical simulations, we show that the numerical simulations agree better with the present model than with the models reported previously. We also discuss a size dependent correction to the electron collision frequency which takes into account electron collisions with SRR walls.

Dispersion of Linear and Nonlinear Optical Susceptibilities in Calcium Neodymium Oxyborate Ca4NdO(BO3)3−LDA versus GGA

We have performed ab inito theoretical calculations of the electronic structure and the linear and nonlinear optical susceptibilities for calcium neodymium oxyborate Ca4NdO(BO3)3 using two approximations for the exchange correlation (XC) potentials, the local density approximation (LDA) and the generalized gradient approximation (GGA). Our calculations show that this compound is metallic-like, with density of states at the Fermi energy E(F), N(E(F)), of 5.95 and 10.33 states/Ry-cell or bare electronic specific heat coefficients of 1.03 and 1.79 mJ/mol-K2 for LDA and GGA, respectively. The overlap between the valence and conduction bands is strong, resulting in metallic behavior. We found that Nd-s/p/d, Ca-s/p, B-p, and O-s/p states controlled the overlapping around E(F). The effect of LDA and GGA on the band structure, density of states, and linear optical properties is very small, while for the nonlinear optical properties, it is very pronounced. Our calculations show that χ(111)(2)(ω) is the dominant component for both LDA and GGA. We find opposite signs of the contributions of the 2ω and 1ω inter/intraband to the real and imaginary parts for the dominant component throughout the wide optical frequency range.