Electrooptic waveguide switch using total internal reflection

An optical switching experinteml Based; ob the electrooptic control of total internal reflection of light in a Ti/LiNbO₃ planar waveguide is reported The device uses a refractive index gap, formed by only applying a voltage The operating principles and characteristics are discussed. The dependence of the switching efficiency on the mode depth is investigated in detail.     

Modelling of self-aligned total internal reflection waveguide mirrors: an interlaboratory comparison

Results of modelling of light propagation in 45° self-aligned total internal reflection rib waveguide mirrors on InP substrate are compared. Six laboratories participated in the comparison with the following six modelling methods: the standard fast-Fouriertransform beam propagation method (BPM), the standard finite-difference (FD) BPM using the Crank-Nicholson scheme (two laboratories), the FD-BPM with the correction for the slowly varying envelope approximation, the method of lines, the eigenmode expansion and propagation method, and a simple method based on the field overlap. All the laboratories used the effective-index method to reduce the three-dimensional problem to two dimensions. The differences among the results obtained by different methods are briefly discussed and qualitatively compared to measured values.     

High-order mode of polymeric waveguide selective excitation

Conditions for the selective excitation of multimode waveguide high-order modes by power trans-formation of fundamental modes of a tunnel connected waveguide are calculated. It is shown that the power conversion factor can reach 100% under phase-matching conditions, which can be satisfied by the selection of a second waveguide refractive index.     

Optical bistability and modulation of light in a thin-film resonator based on total internal reflection

An approximate theoretical analysis is given of the bistable behavior of a simple resonator based on total internal reflection. It is assumed that the medium within the resonator is simultaneously absorbing and nonlinear. It is found that the amplitude bistability characteristics can be comparable to analogous characteristics for more complicated total-internal-reflection structures whose operation is based on tunnel excitation of waveguide modes. It is shown that strong phase bistability is possible in nonabsorbing total-internal-reflection resonators, and the possibility of using total-internal-reflection resonators as light modulators is discussed. Zh. Tekh. Fiz. 67, 38–42 (December 1997)     

Radiation transport and internal reflection in a sphere

We construct an integral equation for the flux intensity in a scattering and absorbing medium using the integro-differential form of the radiative transfer equation in a sphere. The sphere is uniformly irradiated by an external source of arbitrary angular distribution. The Fresnel boundary conditions, which incorporate reflection and refraction, are used. For the special cases of a non-scattering medium, and in the limit of an optically transparent medium, we obtain exact solutions for specular and diffuse refection. Some numerical examples are given which give qualitative agreement with some recent work of Tian and Chiu (JQSRT, 2005).     

Controlled two-pulse generation in Q-switch mode from a single laser using Q-modulator with frustrated total internal reflection

In this work a cavity design for double-pulse generation in Q-switched mode from a single laser is proposed, based on the construction of a second laser channel using a FTIR (frustrated total internal reflection) Q-modulator. A time interval between the two pulses from 500 ns to 120 μs is obtained in a Nd:YAG laser. A comparison with other methods and cavity designs for double-pulse generation is presented. The case when this technique is applied on a tunable laser with metastable upper laser level (Cr:LiCAF, Cr:LiSAF, Alexandrite, Co:MgF₂ or other) is also considered. Even though the method presented in the paper does not rely only on the cavity configuration proposed, some advantages can be obtained – both polarization and wavelength-independent tuning without polarization and wavelength restrictions in combination with the possibility of different wavelengths and polarizations in each pulse. Moreover, by using an active medium generating wavelengths around and up to 3 μm, the Pockels-cell-Q-switch optical transmission problems can be avoided. Received: 9 May 2001 / Revised version: 2 August 2001 / Published online: 15 October 2001     

Three-dimensional total internal reflection microscopy

We investigate the inverse-scattering problem that arises in total internal reflection microscopy. An analytic solution to this problem within the weak-scattering approximation is used to develop a novel form of three-dimensional microscopy with subwavelength resolution.     

Intensification of acoustic beams in crystals at mode conversion near total internal reflection

Geometrical conditions under which mode conversion occurs in a crystal near total internal reflection of an acoustic beam are found. In this case, the entire energy of an incident pump wave is spent on the excitation of a narrow intense reflected beam close in structure to an eigenmode. A consistent choice of orientations of the sagittal plane and surface that excludes the reflection of a parasitic wave of leakage is found.     

Pumping of electromagnetic energy via multiple total internal reflection from active media

An experiment for strong light amplification at multiple total reflections from active gaseous media is proposed.     

Frustrated total internal reflection from thin-layer structures with a metal film

Optics and Spectroscopy - Formulas of the model of a conducting surface for calculating the reflection coefficient and phase shift of light reflected from a thin metal film at the interface between...     

Frustrated total internal reflection evanescent switching

The mechanism of frustrated total internal reflection was analyzed according to the theory of optical film. The transmission and reflection functions were developed and the curves of transmission and reflection changing from the relative gap width d/λ, incident angle θ₀, and refraction index n were shown in graphs. We proposed a scheme of experimental device to test the theoretical conclusion. A self-made electronic actuator drove the piezoelectric ceramics of FTIR. Experiments showed that the evanescent of transmission is 80% for He–Ne laser and smaller for YAG laser and Er:glass laser.     

Subdiffraction resolution in total internal reflection fluorescence microscopy with a grating substrate

We propose a fluorescence surface imaging system that presents a power of resolution beyond that of the diffraction limit without resorting to saturation effects or probe scanning. This is achieved by depositing the sample on an optimized periodically nanostructured substrate in a standard total internal reflection fluorescence microscope. The grating generates a high-spatial-frequency light grid that can be moved throughout the sample by changing the incident angle. An appropriate reconstruction procedure permits one to recover the fluorescence amplitude from the images obtained for various incidences. Simulations of this imaging system show that the resolution is not limited by diffraction but by the period of the grating.     

Nonlinear total internal reflection of electromagnetic waves

We study the stationary solution of an unstable system of interacting inhomogeneous electromagnetic waves and an acoustic wave. It is shown that the instability of this system is of hard type and the threshold of its vanishing is smaller than the excitation threshold. When the amplitude of the incident wave exceeds the threshold value there occurs interaction with partial nonlinear layer transmission, which is changed by large reflection for a large wave amplitude. In this case, the total reflection in the direction opposite to the incident wave and in the specular direction can be greater than in the absence of interaction. A parameter region in which the backward reflection dominates the specular reflection is shown. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 9, pp. 1132–1143, September, 1997.     

Analysis of alternative configurations for a total internal reflection microscope

Numerical analysis of different configurations of a microscope based on evanescent wave trans- formation using total internal reflection was carried out using the discrete sources method.     

Two-dimensional coupled mode equation for grating waveguide excitation by a focused beam

The problem of grating coupling of a focused incident beam under non-normal incidence into a slab waveguide is given a complete three-dimensional (3D) solution. The diffracted field is expressed as the Fourier integral of a regular part and of a singular part resulting from the existence of the coupled guided mode. A suitable expression of the field in the neighborhood of the pole and a rigorous definition of the modal field lead to a generalized coupled mode equation relating the incident field and the two-dimensional (2D) modal field propagating in the plane of the slab waveguide. The phenomenological parameters involved in the coupled wave equation: the propagation constant, the radiation coefficient as well as the modal field shape are derived from the exact treatment of plane wave diffraction in the same structure. The solution of the complete coupling problem is given in the particular case of a Gaussian incident beam, and of a high index step-index waveguide.     

A total internal reflection device using KTN

A total internal reflection diffraction device has been constructed using a quadratic electro-optic material (KTN). This device exhibits a best zero order extinction voltage of 40 V, and a capacitance of 630 pf at room temperature (20° C above Curie temperature). Useful modulation is achieved with coarse gratings (0.4 mm pitch at 0.63m) and mildly striated material can often be used.