Wide-band/angle Blazed Surfaces using Multiple Coupled Blazing Resonances

Abstract

Blazed gratings can reflect an oblique incident wave back in the path of incidence, unlike mirrors and metal plates that only reflect specular waves. Perfect blazing (and zero specular scattering) is a type of Wood’s anomaly that has been observed when a resonance condition occurs in the unit-cell of the blazed grating. Such elusive anomalies have been studied thus far as individual perfect blazing points. In this work, we present reflective blazed surfaces that, by design, have multiple coupled blazing resonances per cell. This enables an unprecedented way of tailoring the blazing operation, for widening and/or controlling of blazing bandwidth and incident angle range of operation. The surface can thus achieve blazing at multiple wavelengths, each corresponding to different incident wavenumbers. The multiple blazing resonances are combined similar to the case of coupled resonator filters, forming a blazing passband between the incident wave and the first grating order. Blazed gratings with single and multi-pole blazing passbands are fabricated and measured showing increase in the bandwidth of blazing/specular-reflection-rejection, demonstrated here at X-band for convenience. If translated to appropriate frequencies, such technique can impact various applications such as Littrow cavities and lasers, spectroscopy, radar, and frequency scanned antenna reflectors.

Unveiling the Properties of Metagratings via a Detailed Analytical Model for Synthesis and Analysis

“…The detailed model, verified with full-wave simulations of realistic physical structures, thus provides both a set of efficient semianalytical tools for synthesis and analysis, and physical insight regarding the dominant processes taking place within the device. Our observations also highlight the immense potential of these devices for a variety of wave-manipulating devices, in consistency with previous reports [40][41][42][43][44][45]. In particular, when suitable working points are chosen, these metagratings can split a normally-incident beam into two equal-power beams propagating at very large oblique angles (∼ 80 • ) with minimal absorption, moderate bandwidth, and substantial resilience to fabrication inaccuracies.…”

“…Very recently, several authors have revisited the problem of perfect reflection, aiming at fully-coupling a plane wave incoming from a given angle to a reflected plane wave propagating towards a desirable (non-specular) direction, based on diffraction grating principles [40][41][42][43][44][45]. This problem, which was recently shown to be quite challenging to solve using metasurfaces [7-9, 46, 47], turned out to be fully solvable with periodic structures, having only a single or a few subwavelength meta-atoms in each macro-period (whose dimensions are comparable to the wavelength).…”

Electronically-tunable resonant blazed metasurface grating

“…In this work, we design and demonstrate an electronically tunable resonant blazed MS grating with no moving parts, to control the blazing frequency and scattering angle of operation, with its principle depicted in Figure 1 (b). We utilize a fixed period resonant grating similar to [4,5], but tune the internal resonance in each period using surface mount varactor (SMV), achieving a tunable 3 blazed surface. Bi-static radar measurements with fixed incident angle show that the scattered wave scans as the bias changes.…”

“…Recently, low-profile blazed grating designs using metasurfaces (MSs) and equivalent resonant structures have been reported in [3][4][5]. MSs are practically very thin structures engineered for controlling phase and magnitude of local wave, and can be used to shape the scattered wave-front.…”

“…The reported planar blazed gratings are achieved either by phasemodulated metasurfaces [3], or by resonant element(s) e.g. resonant strip(s) in the unit-cell [4,5], as shown in Figure 1 (a). Besides its simple design and strong blazing performance, the 2 resonant blazed MS grating of [4,5] have a unique fundamental operation that opens a door to further tailor the blazing operation.…”