Abstract
Electromagnetically induced transparency (EIT) is a pump-induced narrowband transparency window within an absorption line of the probe beam spectrum in an atomic system. In this paper we propose a way to bring together the all-dielectric metamaterials to have EIT-like effects and to optically tune the response by hybridizing them with a layer of a phase change material. We propose a design of the metamaterial based on Si nanoresonators that can support an EIT-like resonant response. On the top of the resonators we consider a thin layer of a chalcogenide phase change material, which we will use to tune the optical response. Our choice is Ge2Sb2Te5 (GST), since it has two stable phases at room temperature, namely amorphous and crystalline, between which it can be switched quickly, nonvolatively and reversibly, sustaining a large number of switching cycles. They differ in optical properties, while still having moderately low losses in telecom range. Since such dielectric resonators do not have non-radiative losses of metals around 1550nm, they can lead to a high-Q factor of the EIT-like response in this range. Firstly, we optimize the starting structure so that it gives an EIT-like response at 1550 nm when the GST layer is in the amorphous state. Our starting design uses glass as a substrate, but we also consider implementation in SOI technology. If we then switch the thin layer of GST to its crystalline phase, which has higher losses, the EIT-like response is red shifted, providing around 10:1 contrast at 1550nm. This reversible tuning can be done with an ns visible pulsed laser. We discuss the results of the simulation of the dielectric metasurface for different configurations and the tuning possibility.
Highlights
Observation of a narrowband transparency window within a wide absorption line of the spectra in atomic physics is known as electromagnetically induced transparency (EIT) [1]
In this paper we propose a way to bring together the all-dielectric metamaterials to have Electromagnetically induced transparency (EIT)-like effects and to optically tune the response by hybridizing them with a layer of a phase change material
We propose a design of the metamaterial based on Si nanoresonators that can support an EIT-like resonant response
Summary
Observation of a narrowband transparency window within a wide absorption line of the spectra in atomic physics is known as electromagnetically induced transparency (EIT) [1]. A potential solution is the use of phase change materials (PCM) that can be quickly, nonvolatively, and reversibly switched between the two stable phases that differ in electrical and optical properties If such a layer is put in contact with our designed structure, the changes in complex refractive index would produce a huge change in optical properties of the overall structure, allowing the manipulation of the incoming beam [18,19,20,21]. For these purposes the PCMs used are chalcogenide glasses that switch between crystalline and amorphous phase upon a heat stimulus. We perform transient thermal calculations to monitor this switching by a pump beam of the visible wavelength, where GST absorbs efficiently - a pump beam induces amorphization or crystallization, leading to the switching of the probe response at 1.55μm between EIT-like resonance, and transmission dip, respectively
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