Wide-Band/Angle Blazed Dual-Mode Metallic Groove Gratings

A simple approach to acquire wide-band/angle blazing operation in 1-D metallic gratings is investigated by means of mode-matching and equivalent circuit analysis. The gratings are single-groove perfectly conducting gratings that support two propagating guided modes (opposed to typical single-mode cases). It is shown under what conditions one can achieve blazing over a wide range of frequencies and angles. Most importantly, it is identified what governs blazing, in particular the true matching condition that needs to be satisfied, and how the structures' multiple resonances play role in achieving such matching and tailoring the bandwidth. Parameters of the proposed equivalent circuit model for the case of the transverse magnetic (TM) polarization are analytically derived. The accuracy of the models is verified through a comparison against the results of full-wave simulations. The procedure to achieve wide-band/angle blazing performance is delineated, and the design parameters are explicitly given. It is shown that this structure can strongly transfer the power of the TM polarized incident wave to the -1st diffraction order with a fractional bandwidth of ≈50% at working frequency $f_{0}=10$ GHz and for -10 dB specular reflection loss, thus realizing a broadband structure. From the circuit model, an insightful discussion is presented at various mechanisms at play when Bragg and off-Bragg blazing occurs and fully justifies the behavior of the device. The proposed technique opens up new vistas in a wide range of applications, such as spectroscopy, Littrow cavities, beam splitters, refractive index biosensors, and frequency scanned antenna reflectors.