Alexandre V. Tishchenko

An intelligible explanation of highly-efficient diffraction in deep dielectric rectangular transmission gratings.

This paper describes in a very easy and intelligible way, how the diffraction efficiencies of binary dielectric transmission gratings depend on the geometrical groove parameters and how a high efficiency can be obtained. The phenomenological explanation is based on the modal method. The mechanism of excitation of modes by the incident wave, their propagation constants and how they couple into the diffraction orders helps to understand the diffraction process of such gratings and enables a grating design without complicated numerical calculations.

Investigation of the polarization-dependent diffraction of deep dielectric rectangular transmission gratings illuminated in Littrow mounting.

Dielectric transmission gratings with a similar period as the wavelength of the incident light can exhibit strong polarization dependence. By optimizing the groove width of a negative first-order Littrow transmission grating it can be achieved that light is transmitted to the zeroth order for one polarization, regardless of the groove depth, while it is efficiently diffracted for the other polarization. An investigation of this remarkable effect, based on a modal field representation inside the grating, as well as experimental results are presented.

Numerical demonstration of the validity of the Rayleigh hypothesis.

The Rayleigh hypothesis and the related method of diffraction analysis are revisited. It is shown that the Rayleigh method can be applied to deep grating modeling without numerical problems and that it gives any desired accuracy whatever the groove depth. This proves the validity of the Rayleigh hypothesis and rehabilitates the Rayleigh method.

Spatially and polarization resolved plasmon mediated transmission through continuous metal films

The experimental demonstration and characterization is made of the plasmon-mediated resonant transmission through an embedded undulated continuous thin metal film under normal incidence. 1D undulations are shown to enable a spatially resolved polarisation filtering whereas 2D undulations lead to spatially resolved, polarization independent transmission. Whereas the needed submicron microstructure lends itself in principle to CD-like low-cost mass replication by means of injection moulding and embossing, the present paper demonstrates the expected transmission effects on experimental models based on metal-coated photoresist gratings. The spectral and angular dependence in the neighbourhood of resonance are investigated and the question of the excess losses exhibited by surface plasmons is discussed.

The Leaky Mode Resonance Condition Ensures 100% Diffraction Efficiency of Mirror-Based Resonant Gratings

The resonance condition of a leaky mode propagating in a dielectric multilayer, which is supported by a mirror and excited by a free-space wave from the cover medium, is simply derived from the phase of the reflection at the mirror and cover interfaces. The leaky mode resonance is used to obtain 100% first-order diffraction efficiency in a reflection resonant grating by destructive interference in the direction of Fresnel reflection. A number of examples support the validity of this condition for high efficiency and illustrate the usefulness of this intelligible representation of the diffraction phenomena for the synthesis of novel diffractive elements.

Azimuthally polarized laser mode generation by multilayer mirror with wideband grating-induced TM leakage in the TE stopband

A new intracavity laser polarization-mode selection scheme relying upon a TE/TM diffractive dichroism principle in a grating multilayer mirror is proposed and demonstrated. The grating diffracts the first orders between the TE and TM band edges of the angular spectra of the laser mirror inducing a leakage of the TM polarization into the mirror substrate through the multilayer stack whereas TE diffraction into the substrate is forbidden. This mechanism is non-resonant, thus relatively wide-band. Applied with a circular-line grating in the 1.0 µm - 1.1 µm wavelength range, this mirror filters out the radially polarization mode and causes the emission of the azimuthally polarized mode. An original amorphous silicon grating technology was developed and the optical function demonstrated in a Nd:YAG laser.

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.

Scaling rules for the design of a narrow-band grating filter at the focus of a free-space beam

The synthesis of a narrow band, wide angular aperture 1D grating filter exhibiting close to 100% reflection of a focused beam is developed analytically on the basis of a phenomenological coupled wave representation.

Bridging pole and coupled wave formalisms for grating waveguide resonance analysis and design synthesis

The algebraic polar expression of resonant reflection from a grating waveguide excited by a free space wave is formulated in terms of the physically meaningful phenomenological parameters of the coupled wave formalism. The reflection coefficient is simply represented as a circle in the complex plane which sheds light on the behaviour of the modulus and phase of anomalous reflection. Analytical expressions are derived for the phenomenological parameters that can now be calculated from optogeometrical quantities which are simple to measure. The relevance and usefulness of bridging the two formalisms is shown in the example of the design of an evanescent wave biosensor.

Fano-like resonance emerging from magnetic and electric plasmon mode coupling in small arrays of gold particles

In this work we theoretically and experimentally analyze the resonant behavior of individual 3 × 3 gold particle oligomers illuminated under normal and oblique incidence. While this structure hosts both dipolar and quadrupolar electric and magnetic delocalized modes, only dipolar electric and quadrupolar magnetic modes remain at normal incidence. These modes couple into a strongly asymmetric spectral response typical of a Fano-like resonance. In the basis of the coupled mode theory, an analytical representation of the optical extinction in terms of singular functions is used to identify the hybrid modes emerging from the electric and magnetic mode coupling and to interpret the asymmetric line profiles. Especially, we demonstrate that the characteristic Fano line shape results from the spectral interference of a broad hybrid mode with a sharp one. This structure presents a special feature in which the electric field intensity is confined on different lines of the oligomer depending on the illumination wavelength relative to the Fano dip. This Fano-type resonance is experimentally observed performing extinction cross section measurements on arrays of gold nano-disks. The vanishing of the Fano dip when increasing the incidence angle is also experimentally observed in accordance with numerical simulations.