Altering infrared metamaterial performance through metal resonance damping

Abstract

Infrared metamaterial design is a rapidly developing field and there are increasing demands for effective optimization and tuning techniques. One approach to tuning is to alter the material properties of the metals making up the resonant metamaterial to purposefully introduce resonance frequency and bandwidth damping. Damping in the infrared portion of the spectrum is unique for metamaterials because the frequency is on the order of the inverse of the relaxation time for most noble metals. Metals with small relaxation times exhibit less resonance frequency damping over a greater portion of the infrared than metals with a longer relaxation time and, subsequently, larger dc conductivity. This leads to the unexpected condition where it is possible to select a metal that simultaneously increases a metamaterial's bandwidth and resonance frequency without altering the geometry of the structure. Starting with the classical microwave equation for thin-film resistors, a practical equivalent-circuit model is developed predicting the sensitivity of infrared metamaterials to complex film impedance. Several full-wave electromagnetic models are developed to validate the resonant-circuit model, and excellent agreement is demonstrated between modeled and measured results.

Array truncation effects in infrared frequency selective surfaces

“…The term metasurface has been introduced as a description for metamaterials consisting of planar periodic arrays of scatterers or apertures which form a surface much thinner than the design wavelength [7][8][9][10][11][12]. In many cases, the desired performance is obtained by employing metamaterial designs inspired by frequency selective surfaces (FSS) whose functionality was shown long ago for radio communications [13][14][15][16].…”

Ultrawide electrical tuning of light matter interaction in a high electron mobility transistor structure

“…From the quality factor of the resonance at 1.71 THz, we estimated the losses to be around 0.85 THz. On cooling the sample, the cavity resonance will be blue shifted according to45: , where ω 0 is the bare cavity resonance without any losses, ω r is the resonance of the MMs including losses and γ is proportional to the combined effect of ohmic losses in the metal and radiative damping in the cavity. The resulting resonance frequency without losses is calculated to be 1.9 THz, which is very close to the observed resonance at 4.2 K.…”

Near- and far-field measurements of phase-ramped frequency selective surfaces at infrared wavelengths

“…23 The higher absorptance has been shown previously to be primarily due to the lower conductivity of metals at infrared wavelengths, especially aluminum, compared to at much lower frequencies where the conductivity of metals are much greater. 31,32 Also, the absorptance can be affected by the thickness of the dielectric layer. 4,8 However, except for the middle size structure, all the remaining structures are detuned from resonance.…”