Anomalous Optical Transmission Research Articles

Experimental observation of sub-radiant longitudinal mode and anomalous optical transmission in metallic wire meshes

In conventional plasmonic media and plasmonic metamaterials, such as metallic wire meshes, a longitudinal mode of an electromagnetic wave manifests itself in frequency overlapping transverse modes, which impedes clear observation of longitudinal-mode-specific physical effects. Through interlacing two sets of wire meshes, an ideal band for the longitudinal mode is achieved ranging from zero frequency to plasma frequency, where transverse modes are completely forbidden. The unique spectral separation of modes facilitates the observation of pure longitudinal modes and related plasmonic effects in a bulk medium. We report the microwave experiment of anomalous optical transmission, induced solely by electromagnetic longitudinal mode resonance, below the plasma frequency in such a wire mesh medium.

Anomalous Optical Transmission Phenomena in Photonic Crystals

Anomalous optical transmission phenomena have ever been discovered in various metamaterials, which can be modulated more easily in Photonic crystals (PhCs). Compared with the regular PhCs composed of round rods closely packed in air, the equal frequency contours (EFC) of honeycomb lattice PhCs constituted by trigonal rods are more rounded and more suitable to realize the all-angle left-handed negative refraction (AALNR) in the low band region. Due to the hex EFC distribution, the regular PhC can be applied in the optical collimator design. In the higher band regions, the more complicated refraction behaviors can be excited based on the intricate undulation of one band or the overlap of different bands in PhCs. These unique features will provide us with more understanding of electromagnetic wave propagation in PhCs and give important guideline for the design of new type optical devices.

Transparent Conducting Silver Nanowire Networks

We present a transparent conducting electrode composed of a periodic two-dimensional network of silver nanowires. Networks of Ag nanowires are made with wire diameters of 45-110 nm and a pitch of 500, 700, and 1000 nm. Anomalous optical transmission is observed, with an averaged transmission up to 91% for the best transmitting network and sheet resistances as low as 6.5 Ω/sq for the best conducting network. Our most dilute networks show lower sheet resistance and higher optical transmittance than an 80 nm thick layer of ITO sputtered on glass. By comparing measurements and simulations, we identify four distinct physical phenomena that govern the transmission of light through the networks: all related to the excitation of localized surface plasmons and surface plasmon polaritons on the wires. The insights given in this paper provide the key guidelines for designing high-transmittance and low-resistance nanowire electrodes for optoelectronic devices, including thin-film solar cells. For the latter, we discuss the general design principles to use the nanowire electrodes also as a light trapping scheme.

Optical transmission coefficient of crystalline [N(CH3)4]2MeCl4 in the incommensurate phase

This a study of the optical transmission of [N(CH3)4]2ZnCl4 and [N(CH3)4]2CuCl4 crystals in the incommensurate phase when a defect density wave is present. It is found that an anomalous reduction in the transmission coefficient is caused by scattering of light owing to a realignment of the superstructure during transitions between metastable states. When a defect density wave is present, the anomalous optical transmission of the crystal is related to the scattering of light on superstructure inhomogeneities produced by a superposition of existing modulation waves.

Anomalous optical transmission through a vortex lattice in a film of type-II superconductor

Anomalous optical transmission through a vortex lattice in a film of type-II superconductor

Physical nature of anomalous optical transmission of thin absorptive corrugated films

The enhancement of p-polarized light transmittance through periodically relief thin absorptive film on dielectric or semiconductor substrate was considered theoretically. The calculation of transmittance/reflectance was performed in the framework of modified differential formalism method. Numerical results obtained for noble metals (Au, Ag and Cu) under arbitrary relief correlation between two sides of film allow ascertaining physical nature of surface electromagnetic fields responsible for the enhancement transmittance effect. These are Fano, Zenneck-Sommerfeld and Brewster modes on the interfaces with absorbing medium. For anticorrelated reliefs of opposite film surfaces the bound of their modes was found especially effective.

Femtosecond laser fabrication of apertures on two-dimensional microlens arrays

Two-dimensional lattices of microspheres formed by self-assembly from colloidal solutions can be employed as microlens arrays. With applications in confocal microscopes, some types of parallel laser-surface processing or devices based on anomalous optical transmission, it is useful to improve the imaging properties of microspheres by generating an aperture on each of these lenses. This has been achieved by means of laser-induced forward transfer using femtosecond Ti:sapphire laser radiation. Some of the peculiarities observed in the experiments can be understood on the basis of field intensity calculations.

Anomalous optical transmission due to strain-induced optical axis rotation in optical fibers embedded in concrete

We report the observation of anomalous optical transmission in polarimetric optical fibers embedded in concrete cylinders. The optical transmission intensities vary nonsinusoidally as a function of the applied strain. We show that this phenomenon can be explained with a theoretical model taking into account the strain-induced rotation of the birefringence axes, as a result of the photoelastic effect in the presence of shear strains, and the optical transitions between different sections of the fiber with rotated principal axes in the sensing region. Our theoretical results agree very well with the experimental observations. We also present experimental evidence on the effects of residual strains in the fibers embedded in concrete cylinders after tests.

Anomalous optical transmission in homogeneous latex suspensions.

We have observed a deviation from the law of exponential attenuation of a 633-nm optical beam in a homogeneous scattering medium in the low-intensity limit, where nonlinear optical effects or thermal effects are insignificant (Bouguer's law). This deviation occurs when the spatial correlation length is comparable to or larger than the asymptotic attenuation length, whence the assumption of independent scattering events is violated. We develop a statistical model for the optical dielectric fluctuations which fits well our nonexponential beam-transmission data in homogeneous suspensions of 1-\ensuremath{\mu}m latex spheres. We use this to determine the correlation lengths (7 to 12 \ensuremath{\mu}m) of the dielectric fluctuations in these suspensions. These correlation lengths are consistent with values that we deduce from the observed angular spreads of forward light scattering.