Abstract
AbstractActive control of chirality in artificial media such as metamaterials is fundamental in many scientific areas, ranging from research into fundamental optical phenomena to the investigation of novel materials, spectroscopy, and imaging. Precise control of the light polarization states has great importance for light‐matter interaction in chemistry and biology, as media with diverse chiral properties react differently to the incoming polarization of light. In this work an active double layer metamaterial device based on vertically stacked ring resonators is realized by integrating electrostatically tunable graphene as an active element. The device is characterized with a THz time domain spectroscopic system demonstrating an all‐electrical control of circular dichroism and optical activity at ≈2 THz, reporting a tunable ellipticity of 0.55–0.98 and >20° rotation of the plane polarization, respectively, by modifying the conductivity of graphene. Further integration with a narrow frequency quantum cascade laser emitting at ≈1.9 THz, in a crossed polarizer experimental arrangement, realizes an active amplitude modulator, hence highlighting the versatility of this approach. These results represent an important milestone for the investigation of novel concepts in optics and in several applications in the THz range, such as wireless communications and spectroscopy.
Highlights
Active control of chirality in artificial media such as metamaterials is funcular polarized (RCP) and left-handed damental in many scientific areas, ranging from research into fundamental optical phenomena to the investigation of novel materials, spectroscopy, and imaging
Circular dichroism is determined by the different absorption for light. In this circular polarized (LCP) and RCP waves in a chiral medium, causing a linear to elliptical polarithe THz range, such as wireless communications and spectroscopy
In this article we report on the realization of a double layer active MM polarization device capable of achieving circular dichroism (CD) with a dynamic ellipticity modulation of ≈0.45 at 2.13 THz
Summary
MMs coupled to graphene showed efficient modulation via iongel electrical gating.[44] In this article we report on the realization of a double layer active MM polarization device capable of achieving CD with a dynamic ellipticity modulation of ≈0.45 at 2.13 THz. Differently from other approaches based on the tunable selective absorption between RCP and LCP, such as in double layer inverse gammadions,[5,48] the chiral response here was achieved due to the interplay between dark and bright MM resonances, reminiscent of electromagnetic induced transparency. These results pave the way to a plethora of experimental configurations where an active modulation of the THz light polarization is required
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