Using Low-Loss Phase-Change Materials for Mid-Infrared Antenna Resonance Tuning

Abstract

We show tuning of the resonance frequency of aluminum nanoantennas via variation of the refractive index n of a layer of phase-change material. Three configurations have been considered, namely, with the antennas on top of, inside, and below the layer. Phase-change materials offer a huge index change upon the structural transition from the amorphous to the crystalline state, both stable at room temperature. Since the imaginary part of their permittivity is negligibly small in the mid-infrared spectral range, resonance damping is avoided. We present resonance shifting to lower as well as to higher wavenumbers with a maximum shift of 19.3% and a tuning figure of merit, defined as the resonance shift divided by the full-width at half-maximum (FWHM) of the resonance peak, of 1.03.

Broad electrical tuning of plasmonic nanoantennas at visible frequencies

“…3(a), the tuning figure of merit is 1.05, which is the largest value reported for electrical tuning of plasmonic nanoantennas in the visible spectral region. Our observed value is comparable with the previously reported value of 1.03 for a mid-infrared antenna 34 and significantly larger than that for a tunable near-infrared metamaterial based on VO 2 phase transition, where a value of 0.14 was observed. 33 Additionally, we extracted the difference in the absorption, 35 or contrast, of the device under a bias voltage with respect to the absorption at zero voltage.…”

“…33,34 For the structure measured in Fig. 3(a), the tuning figure of merit is 1.05, which is the largest value reported for electrical tuning of plasmonic nanoantennas in the visible spectral region.…”

All-dielectric phase-change reconfigurable metasurface

“…The induced index change of $10% is substantial but yet smaller and less wavelength-dependent than may be expected on the basis of ellipsometric data for unstructured crystalline GST. 33 This indicates strongly that the nanostructured GST is stoichiometrically modified and/or only partially crystallized, 5,36,37 which is to be anticipated primarily as a consequence of the FIB milling process (reduction of refractive index due to irradiation, 38 creation of defects and gallium implantation) and because nanostructuring unavoidably modifies the thermal properties of the film (i.e., the energy absorbed from the laser beam at a given point; the temperature achieved; and the rates of temperature increase/ decrease).…”

“…1 Phase-change materials, including chalcogenides, [2][3][4][5] vanadium dioxide, [6][7][8] gallium, 9 and liquid crystals, [10][11][12] have featured prominently in this evolution. We now show that the chalcogenides offer a uniquely flexible platform for the realization of non-volatile, optically-switchable alldielectric metamaterials.…”

Photoinduced tunability of the reststrahlen band in4H−SiC

“…Therefore, even given the additional broadening, the quality factor is still significantly higher than any reported plasmonic systems (a survey of such Q factors in both SPP and SPhP materials may be found in Ref. [11]), and the modulation depth is comparable to the highest tuning ranges reported for plasmonic systems [31,32]. Additionally, a major benefit of the tuned SPhPs is that their linewidths are much narrower than their plasmonic counterparts, so the former could potentially be applied to modulated surface enhanced IR (SEIRA) techniques.…”