V A Sychugov

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.

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.

Shift of light frequency in taper fiber under the action of acoustic pulse

Theory and the first experimental results concerned interaction between a traveling acoustic wave and light wave of whispering gallery modes in glass cylinders with variable cross-section along their length are presented. It is shown theoretically that gradual shift of light frequency by tens of percents can be obtained in a frequency converter based on a glass cone.

Technique for determining the cell parameters of the confined one-dimensional photonic crystal, based on the Floquet-Bloch formalism

The technique for determining the cell structural parameters of the confined one-dimensional photonic crystal, based on the strict analytical representation of Floquet-Bloch waves in the form of inhomogeneous waves is proposed.

Leaky modes and directed modes in confined one-dimensional photonic crystal

Directed modes and leaky modes in a confined one-dimensional photonic crystal are analytically described. The dispersion relation of these modes is written as the transverse resonance condition of Floquet-Bloch waves, taking into account phase shifts at interfaces with adjacent media.

Influence of grating shift in Fabry-Perot interferometer with two waveguide grating mirrors

Fabry-Perot interferometer with two identical waveguide gratings mirrors is studied. Earlier we studied the case of oblique light incidence and in this paper normal incidence is considered. Normal incidence case is special because two waveguide modes propagating in the opposite directions are excited simultaneously. It is found that for the filter having small distance between the waveguide grating mirrors the reflection spectrum depends on the phase shift between the gratings. One or two additional resonances appear in the case of phase shift not being equal to 0 or π. We attribute the appearance of these resonances to the symmetry breakdown in the waveguide system and coupling between the waveguides.

Propagation of a focused light beam in a circuital system of tunnel-coupled waveguides

The propagation of a pencil beam in a circuital system of tunnel-coupled waveguides is considered. It is shown that the beam periodically focuses into a point when moving along the trajectory. A maximal number of waveguides supporting the propagation of the beam can be estimated in simple terms. The cross-sectional area of the waveguides can be subdivided into three zone with the beam pulsing only in the central one.