The effect of a metal layer with negative permittivity on the behavior of nonlinear-magnetoopic isolator is studied.
The isolator consists of Metal film, nonlinear cladding, and magnetooptic substrate. It is found that difference between
forward and backward propagation for TM<sub>0</sub> mode increases with increasing the absolute value of the tuning parameter
which is the permittivity of the metal film, ε<sub>f</sub>. It is also found that the maximum cutoff thickness of the isolator occurs
in selfdefocusing case around η=0.65 and at the highest assumed value of ε<sub>f</sub> = -8. The results are interesting since they
assure the possibility to get maximum optimization of the isolator behavior by adding metallic materials.
Fiber-Bragg-grating (FBG) sensors have become commercially available sensors for the measurement of temperature,
strain and many other quantities. The sensor information is encoded in the spectral reflection characteristic
of these devices. Their usage as strain sensors is one of the most prominent fields of application. Strains
from a structure which is to be monitored are transferred into the fiber-Bragg-grating, by surface bonding or
embedding. In general an arbitrary state of strain may thus occur within the FBG, represented by a full strain
tensor with normal strain components, as well as with shear strain components. The influence of normal strains
is well understood and has been treated theoretically by many authors. The influence of shear strains is however
not well understood. As we were recently able to theoretically demonstrate by a full tensor coupled mode
analysis, shear strains do influence the spectral response of fiber-Bragg-sensors and thus have to be considered.
In this work, an introduction to the modeling of shear strains within fiber-Bragg-gratings is given. We discuss
reasonable approximations for the simplification of the theoretical model. We compute, to our knowledge for
the first time, the direct influence of shear strains on the output of a FBG measurement system and show the
cases when shear strain effects are relevant. Furthermore, we compare the sensitivity of different interrogation
algorithms towards shear strain influences on the measurement system output.
Optical sensors have wide range of application such as in medicine, astronomy, industry, and others. Sensitivity of
symmetric three layered optical waveguide sensor is investigated. The proposed sensor consists of dielectric slab
surrounded by metamaterial (MTM) cladding and MTM substrate. MTMs are new artificial materials which have
simultaneously negative permittivity ε and negative permeability μ. Different values of MTMs parameters ε and μ are
chosen to optimize the sensitivity of the sensor. However, the value of ε<sub>μ</sub> is kept content and equal to 4. The
dispersion equation which represents the effective index <i>n<sub>e</sub></i> for transverse electric modes (TE) as a function of slab
thickness has been derived. A close form solution of the sensitivity (S) which is defined as the variation of the effective
index with respect to Temperature variation is introduced. The sensitivity then numerically calculated as function of the
film thickness at different values of Metamaterial parameters. It is found that sensitivity varies with the film thickness
and depends on the MTMs parameters. These results are important for designing sensors.
Optical waveguide isolators are vital integrated optic modules in advanced optical fiber communication systems. This
study demonstrates an integrated optical isolator which has simple structure consisting of three layers. The thin magnetic
garnet film is sandwiched between linear dielectric cover and metamaterial (MTM) substrate. The effective refractive
indexes for both forward and backward fields are analytically calculated by deriving the dispersion equation of the TM
fields. The difference Δβ between the phase constant for forward and backward propagation is calculated numerically for
different values of MTMs permittivity (ε<sub>s</sub>) and permeability (μ<sub>s</sub>). In all the calculations, the value of ε<sub>s</sub>μ<sub>s</sub> is kept equal to
4. Δβ is also plotted as a function of the film thickness. Results show that the value of Δβ changes with the parameters of
MTMs and the film thickness. This helps in selecting the optimal design for the isolator at which Δβ approaches zero.
The results are encouraging to propose an optical isolator.
Stress effect on the behavior of optical waveguide sensor consists of dielectric slab inserted between metamaterial
(MTM) cladding and substrate is investigated by using numerical calculations. Several MTMs with different values of ε
and μ with ε μ = 4 are chosen in order to clarify the variation of stress effect with respect to the material constants.
Numerical calculations of the effective index for both transverse electric modes (TE) and transverse magnetic modes
(TM) as a function of stress and slab thickness have been performed. It is found that stress affects the performance of
the waveguide sensor.
A theoretical approach to study the influence of temperature stress of the thermal sensitivity effective refractive index for
asymmetrical nonlinear optical waveguides is developed. In the proposed waveguide structure, temperature stress is
induced due to the different thermal expansion coefficients of the substrate, core and cladding. Numerical calculation is
carried out to draw the thermal sensitivities of effective refractive indices against the core thickness for both transverse
electric modes (TE) and transverse magnetic modes (TM). The relation between thermal sensitivities and different
temperature stress gradient is derived and plotted. Based on the results, thermal sensitivity of the sensor can be
controlled by temperature stresses which can be controlled by carefully picking the materials and loading methods.