Angela N. Fantino

Phase resonances in compound metallic gratings

We study the phase resonances that appear in infinite conducting gratings comprising a finite number of grooves in each period (compound gratings), when illuminated by a p-polarized plane wave. In particular, we investigate a surface that separates a lossy conductor from a dielectric isotropic medium. The resonances appear when a particular distribution of the phase of the electromagnetic field inside the cavities takes place, and are identified as peaks in the specularly reflected efficiency. These resonances are accompanied by an intensification of the internal field. The diffraction problem is solved by using the modal method. We use the surface impedance boundary condition, which has been proven to be reliable for metals with high conductivity, and simplifies the numerical treatment.

Czerny-Turner monochromator: astigmatism in the classical and in the crossed beam dispositions

The images obtained with a classical Czerny-Turner design and a crossed beam Czerny-Turner design are compared, imposing in both cases the Fastie and the Pribram and Penchina conditions. The results show that the astigmatic line may be made parallel to the spectral line only with the classical design, which makes it superior to the crossed beam design. Also, the importance of an adequate choice of the construction parameters is shown. The analytical calculations are checked by ray tracing.

Czerny-Turner spectrograph with a wide spectral range

In this work we present the design of a Czerny-Turner spectrograph with practically constant images over a wide spectral range (3500-7500 A). The plate diagram method is used to determine the parameters and the resulting design is evaluated by ray tracing.

Sine Relation for Optical Linear Systems: Matrix Formulation

Abstract The sine relation connects the object, the image, and the entrance and exit-pupil coordinates for centred optical systems. For non-symmetrical systems the object and the image coordinates are related by a matrix. From this we determine another matrix which relates the entrance and exit pupil coordinates. A new expression for the sine relation is given and is valid for all optical linear systems. Finally, the results are applied to a plane grating and the coordinates on the exit pupil are obtained.

Magnetic effects on the reflection of electromagnetic waves at isotropic–uniaxial interfaces

The ellipsometric properties of flat boundaries between isotropic and uniaxial materials with different magnetic permeabilities are studied for three particular orientations of the optic axis. The analysis can be applied either to synthetic anisotropic materials with magnetic properties or to nonmagnetic crystals in contact with magnetic isotropic media. By analysis of noticeable features in the curves of reflectivity versus angle of incidence, the space of constitutive parameters is divided into regions where the reflectivity exhibits very different qualitative behaviors. Some unusual reflection effects, such as the simultaneous existence of Brewster angles for p and s polarizations and the existence of angles for which the reflection matrix is null, are shown to be theoretically possible. Conditions for total reflection and total transmission are investigated and exemplified numerically by means of a parametric study.

Pupil Distortion in a System with Two Arbitrarily Oriented Plane Gratings

Abstract In this work we give the analytical expressions for the pupil distortion generated by a tandem of two plane gratings with constant period and with an arbitrary relative orientation. These expressions have been obtained using the matrix form of the sine relation. In particular, we treat the cases of parallel and perpendicular grooves, and for both the expressions are particularized for parallel gratings. In all cases, in-plane incidence is discussed.

Use of the plate diagram in the fast evaluation of monochromators and spectrographs

In this work we show a geometrical method-the unified plate diagram-which makes it possible to estimate simply and rapidly the dependence of image sharpness aberrations (spherical, coma, and astigmatism) on the basic design parameters of plane grating spectrographic systems. We also present analytical equations with the help of which additional parameters may be adjusted, such as off-axis relations, position, and form of the focal surface.

Resonant effects in compound diffraction gratings

We give numerical evidence of a new kind of resonances that appear in infinite perfectly conducting gratings comprising a finite number of grooves in each period, when illuminated by a normally incident p-polarized plane wave. The resonances appear when a particular distribution of the phase of the electromagnetic field inside the cavities take place, and are identified as sharp peaks in the specularly reflected efficiency. These resonances are accompanied by a significant intensification of the interior field. The cavities considered are rectangular and the diffraction problem is solved for s and p polarization by using the modal method.

Planar interface between a chiral medium and a metal: Surface wave excitation

Abstract The feasibility of excitation of surface waves at a single planar interface is demonstrated numerically. The interface separates a chiral medium from an isotropic and achiral medium; this latter could be a metal. Both media are characterized by their dielectric permittivity and their magnetic permeability. The chiral is also specified by its chiral parameter. As a result it is found that surface wave excitation is theoretically possible. The range of values of the chiral parameter in which surface waves can be excited is very narrow and depends on the constants of both media. The condition that at least one of the media must be dissipative seems to be necessary to have excitation. To obtain these results, the dispersion relation of the interface is deduced. Chiral media are described by the Drude–Born–Fedorov constitutive equations. The exact dependence of the fields on the chiral parameter is kept in the computation.

Shape resonances in nested diffraction gratings

The diffraction problem of a plane wave impinging on a grating formed by nested cavities is solved by means of the modal method, for s and p polarization modes. The cavities are formed by perfectly conducting sheets that describe rectangular profiles. The electromagnetic response of the grating is analyzed, paying particular attention to the generation of resonances within the structure. The dependence of the resonances on the geometrical parameters of the grating is studied, and results of far and near field are shown. The results are checked and compared with those available in the literature for certain limit cases.