Electrodynamic resonance of surface conduction and THz transmission through arrays of rectangular apertures in opaque metallic thin films.

A modal method is developed analytically to investigate the THz optical transmission and reflection of a metallic thin film perforated by a 2D array of rectangular apertures. For subwavelength apertures, this optical model is interpreted in terms of passive electrical circuits, with interface admittances accounting for the THz surface conduction properties of the metallic film. The reactive component of the admittance of the evanescent diffraction cloud is shown to exhibit resonant behavior governed by the shape factors of the array.

Discrete photonics resonator in coupled waveguide arrays.

We demonstrate both theoretically and experimentally that discrete diffraction resonance can be designed, fabricated, and successfully probed in functionalized - guidonic - coupled waveguide arrays. We evidence that double-barrier patterning of the coupling creates wavelength-independent angular tunnel resonance in the transmitted and the reflected intensity of light beams freely propagating in the plane of the array. Transmission peaks obtained are associated with resonant excitation of the engineered array bound supermodes of the functionalized array, in agreement with accurate and practical numerical modeling based on extended coupled-mode theory.

Analytical first-order extension of coupled-mode theory for waveguide arrays.

Coupled mode theory for waveguide arrays is extended to next-nearest neighbor interactions using propagation equations. Both lateral diffraction and propagation of Floquet-Bloch waves are altered respectively by extra coupling and non-orthogonality between isolated waveguide modes. The analytical formula describing the distortions of the diffraction relation is validated by direct numerical simulation for weakly coupled InP and GaAs shallow ridge waveguides and for strongly coupled Si-SiO(2) buried strip waveguides.

Confining light flow in weakly coupled waveguide arrays by structuring the coupling constant: towards discrete diffractive optics.

Structuring the coupling constant in coupled waveguide arrays opens up a new route towards molding and controlling the flow of light in discrete structures. We show coupled mode theory is a reliable yet very simple and practical tool to design and explore new structures of patterned coupling constant. We validate our simulation and technological choices by successful fabrication of appropriate III-V semiconductor patterned waveguide arrays.

Purcell enhancement of spontaneous emission from quantum cascades inside mirror-grating metal cavities at THz frequencies.

Quantum cascade devices processed into double metal cavities with subwavelength thickness and a grating on top are studied at terahertz frequencies. The power extracted from the devices as a function of the device thickness and the grating period is analyzed owing to electrodynamical modeling of dipole emission based on a modal method in multilayer systems. The experimental data thus reveal a strong Purcell enhancement, with Purcell factors up to approximately 50.

Modal method for conical diffraction on a rectangular slit metallic grating in a multilayer structure.

The modal method is applied to the problem of conical diffraction on a rectangular slit metallic grating lying on an arbitrary multilayer medium. In the approximation of the surface impedance boundary condition on the grating walls, a single matrix equation is obtained, whose coefficients are expressed simply by the reflectivities on the different layers. A simple and comprehensive treatment is thus obtained for virtually any multilayer system.