Boris A. Usievich

Long-range surface plasmons in asymmetric layered metal-dielectric structures

Abstract This paper brings the experimental evidence of the existence of the long range plasmon mode in an asymmetrical thin metal film structure. This mode is identified theoretically and experimentally by means of the existence of the effect of abnormal reflection in the presence of a coupling corrugation grating. The use of this grating excited plasmon mode in sensor applications is discussed and early encouraging results are reported. The means for the very fast calculation of the effective index of the modes of a multilayer waveguide structure possibly comprising metal layers are presented.

Analytical treatment of the thermal problem in axially pumped solid-state lasers

A complete analytical analysis of the temperature distribution in a laser rod in an axial pumping scheme is presented. The heat source distribution, as well as the front or side cooling means, have a circularly cylindrical symmetry. The longitudinal heat-source distribution is strongly inhomogeneous.

Anomalous light reflection at the surface of a corrugated thin metal film

The process of excitation of surface electromagnetic waves (SEWs) in corrugated thin metal film is investigated theoretically and experimentally. The existence of an anomalous increase of the reflection coefficient is demonstrated. The excitation of long-range plasmons in thin metal films opens new possibilities for sensor applications.

Optimization and control of grating coupling to or from a silicon‐based optical waveguide

The analysis of a silicon-based step-index waveguide with a corrugation grating at its surface is performed by considering the reflec- tion between the silicon substrate and the optical buffer. The conditions on the silica buffer thickness for maximum in/out coupling into the sub- strate and into the air are given analytically, and a number of features of practical interest are described.

Si3N4/SiO2/Si waveguide grating for fluorescent biosensors

The simulation of the coupling efficiency of fluorescence sources immobilized in the evanescent field of a waveguide mode has allowed the dimensioning of a sensing waveguide platform based on a silicon substrate exhibiting maximum fluorescence efficiency. The incoupling of the excitation light and the outcoupling of the fluorescence signal are performed by means of a corrugation grating. The presence of the highly reflective silicon surface under the waveguide grating causes interferences in the fluorescence output signal which depend on the wavelength and on the radiation angle. A theoretical modeling of the grating coupling under these conditions has led to the achievement of high incoupling efficiency at the excitation wavelength, and simultaneously to high outcoupling efficiency at the wavelength of the fluorescence peak. An experiment was performed with fluorescein at the surface of a 160 nm thick silicon nitride waveguide film on a silicon substrate with a 2100 nm thick buffer layer of silica. The measured outcoupled spectra fit well with the calculated spectra taking into account the output grating coupling, the fluorescence spectrum, and fluorescence coupling. These waveguide grating structures are applied to the detection of immunological reactions.

Spectral and Angular Dependences of the Efficiency of Relief-Phase Diffractive Lenses with Two- and Three-Layer Microstructures

The efficiency of diffractive lenses with two-layer single-relief and three-layer double-relief microstructures is studied. Studies are carried out using the scalar and electromagnetic diffraction theories. Depending on the requirements for the diffractive lens, the theories permit one to justifiably choose the configuration, optical materials, and constructive parameters of the microstructure, as well as to determine the real maximum allowable angle of radiation incidence on the diffractive lens with the microstructure of a particular type.

Multilayer resonances sharpened by grating waveguide resonance

A multilayer planar structure comprising a highly reflective multilayer dielectric mirror and a corrugated waveguide is proposed for use as a narrow passband optical filter. The proposed filter has a much narrower linewidth than a usual Fabry–Perot cavity with two multilayer dielectric mirrors. It is shown that the narrowing of the linewidth is due to the strong spectral dependence of the phase of the wave reflected from the waveguide grating mirror. The shape of the pass band can be made symmetrical by a proper choice of the grating groove profile.

Unidirectional waveguide grating coupling by means of parallelogrammic grooves

The blazing effect of parallelogramic grooves is analyzed theoretically and demonstrated experimentally in the case of TE and TM modes in large guidance waveguides. A novel fabrication method is proposed, modellized and demonstrated.

Surface electromagnetic waves at the interface between a homogeneous medium and a system of coupled waveguides

An analysis is made of the experimental investigations of the surface waves existing at the interface between a homogeneous medium and a periodically stratified medium that represents a bounded system of coupled waveguides. It is shown that, in all cases of the observation of surface waves, the bounded system of coupled waveguides has its own spectrum of guided modes and a spectrum of leaky modes that become surface waves of the system. It is also demonstrated that a biosensor can successfully operate when two surface waves serve as leaky modes of a Bragg waveguide in which the periodic system of waveguides is used as a distributed Bragg mirror of this waveguide. A structure supporting surface waves is designed on the basis of ten pairs of Nb2O5-SiO2 layers and implemented experimentally. The surface waves are detected with a K8 glass prism according to the Kretschmann scheme.

Bragg diffraction of light in a restricted homogeneous system of tunnel-coupled waveguides

A system of tunnel-coupled rectilinear waveguides is studied. The dependence of the number of modes in this system on the number of waveguides N, the distance between the waveguides, and the number of modes in a separate waveguide is considered. It is shown that the modes of the m = N and N + 1 orders in such a system are Bragg modes; i.e., the angle between the direction of their propagation and the system axis is close to the Bragg angle. The effective refractive indices n* of these modes change stepwise. The step size Δn* is found to be dependent on the distance s between the waveguides and on the number of modes in a separate waveguide. A system of single-mode waveguides with the number of guided modes M = 34 < N = 50 is studied experimentally. It is shown that the Bragg modes of the system lie among the leakage modes of the system and have rather low losses. It is demonstrated that the localization of the Bragg modes among the leakage modes may be favorable for their selection upon light generation.