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Numerical study of achiral phase-change metamaterials for ultrafast tuning of giant circular conversion dichroism.

Cao T, Wei C, Mao L - Sci Rep (2015)

Bottom Line: The extrinsically giant 2D chirality appears provided that the rectangular array of the Au squares is illuminated at an oblique incidence, and accomplishes a wide tunable wavelength range between 2664 and 3912 nm in the M-IR regime by switching between the amorphous and crystalline states of the Ge2Sb2Te5.A photothermal model is investigated to study the temporal variation of the temperature of the Ge2Sb2Te5 layer, and shows the advantage of fast transiting the phase of Ge2Sb2Te5 of 3.2 ns under an ultralow incident light intensity of 1.9 μW/μm(2).Our design is straightforward to fabricate and will be a promising candidate for controlling electromagnetic (EM) wave in the optical region.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Dalian University of Technology, 116024 China (P.R.C) 116024.

ABSTRACT
Control of the polarization of light is highly desirable for detection of material's chirality since biomolecules have vibrational modes in the optical region. Here, we report an ultrafast tuning of pronounced circular conversion dichroism (CCD) in the mid-infrared (M-IR) region, using an achiral phase change metamaterial (PCMM). Our structure consists of an array of Au squares separated from a continuous Au film by a phase change material (Ge2Sb2Te5) dielectric layer, where the Au square patches occupy the sites of a rectangular lattice. The extrinsically giant 2D chirality appears provided that the rectangular array of the Au squares is illuminated at an oblique incidence, and accomplishes a wide tunable wavelength range between 2664 and 3912 nm in the M-IR regime by switching between the amorphous and crystalline states of the Ge2Sb2Te5. A photothermal model is investigated to study the temporal variation of the temperature of the Ge2Sb2Te5 layer, and shows the advantage of fast transiting the phase of Ge2Sb2Te5 of 3.2 ns under an ultralow incident light intensity of 1.9 μW/μm(2). Our design is straightforward to fabricate and will be a promising candidate for controlling electromagnetic (EM) wave in the optical region.

No MeSH data available.


Related in: MedlinePlus

3D- FEM simulation of heat power irradiating on an achiral PCMM located at the beam center, where the solid red line presents the heat power irradiating on the structures for LCP incident light, the solid blue line presents the heat power irradiating on the structures for RCP incident light, the dash red line is the temperature of the amorphous Ge2Sb2Te5 layer during one pulse for LCP incident light, the dash blue line is the temperature of amorphous Ge2Sb2Te5 layer during one pulse for RCP incidence.
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f5: 3D- FEM simulation of heat power irradiating on an achiral PCMM located at the beam center, where the solid red line presents the heat power irradiating on the structures for LCP incident light, the solid blue line presents the heat power irradiating on the structures for RCP incident light, the dash red line is the temperature of the amorphous Ge2Sb2Te5 layer during one pulse for LCP incident light, the dash blue line is the temperature of amorphous Ge2Sb2Te5 layer during one pulse for RCP incidence.

Mentions: where τ = 1.5 ns is the time constant of the light pulse, t0 = 3 ns is the time delay of the pulse peak. Figure 5 shows Qs(r, t) and the temperature of the amorphous Ge2Sb2Te5 interlayer for both LCP and RCP incidences at θ = 75°, φ = 60°, where the PCMM is placed at the center of Gaussian beam. As can be seen, the temperature of amorphous Ge2Sb2Te5 for the RCP can reach 433 K at 2.8 ns and maximum 505 K at 4.2 ns under an incident light intensity of 1.9 μW/μm2. Due to heat dissipation to the surroundings, the temperature starts decreasing after 4.2 ns before the next pulse comes. However, Qs(r, t) and the temperature for the LCP are lower than the RCP owing to its smaller absorbance coefficient Ra, where the amorphous-to-crystalline phase transition temperature of 433 K is achieved at 3.2 ns under the same light intensity of 1.9 μW/μm2. Thereby the melting point of 433 K can be obtained to switch the phase of Ge2Sb2Te5 for both LCP and RCP incident light at θ = 75°, φ = 60°.


Numerical study of achiral phase-change metamaterials for ultrafast tuning of giant circular conversion dichroism.

Cao T, Wei C, Mao L - Sci Rep (2015)

3D- FEM simulation of heat power irradiating on an achiral PCMM located at the beam center, where the solid red line presents the heat power irradiating on the structures for LCP incident light, the solid blue line presents the heat power irradiating on the structures for RCP incident light, the dash red line is the temperature of the amorphous Ge2Sb2Te5 layer during one pulse for LCP incident light, the dash blue line is the temperature of amorphous Ge2Sb2Te5 layer during one pulse for RCP incidence.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4589781&req=5

f5: 3D- FEM simulation of heat power irradiating on an achiral PCMM located at the beam center, where the solid red line presents the heat power irradiating on the structures for LCP incident light, the solid blue line presents the heat power irradiating on the structures for RCP incident light, the dash red line is the temperature of the amorphous Ge2Sb2Te5 layer during one pulse for LCP incident light, the dash blue line is the temperature of amorphous Ge2Sb2Te5 layer during one pulse for RCP incidence.
Mentions: where τ = 1.5 ns is the time constant of the light pulse, t0 = 3 ns is the time delay of the pulse peak. Figure 5 shows Qs(r, t) and the temperature of the amorphous Ge2Sb2Te5 interlayer for both LCP and RCP incidences at θ = 75°, φ = 60°, where the PCMM is placed at the center of Gaussian beam. As can be seen, the temperature of amorphous Ge2Sb2Te5 for the RCP can reach 433 K at 2.8 ns and maximum 505 K at 4.2 ns under an incident light intensity of 1.9 μW/μm2. Due to heat dissipation to the surroundings, the temperature starts decreasing after 4.2 ns before the next pulse comes. However, Qs(r, t) and the temperature for the LCP are lower than the RCP owing to its smaller absorbance coefficient Ra, where the amorphous-to-crystalline phase transition temperature of 433 K is achieved at 3.2 ns under the same light intensity of 1.9 μW/μm2. Thereby the melting point of 433 K can be obtained to switch the phase of Ge2Sb2Te5 for both LCP and RCP incident light at θ = 75°, φ = 60°.

Bottom Line: The extrinsically giant 2D chirality appears provided that the rectangular array of the Au squares is illuminated at an oblique incidence, and accomplishes a wide tunable wavelength range between 2664 and 3912 nm in the M-IR regime by switching between the amorphous and crystalline states of the Ge2Sb2Te5.A photothermal model is investigated to study the temporal variation of the temperature of the Ge2Sb2Te5 layer, and shows the advantage of fast transiting the phase of Ge2Sb2Te5 of 3.2 ns under an ultralow incident light intensity of 1.9 μW/μm(2).Our design is straightforward to fabricate and will be a promising candidate for controlling electromagnetic (EM) wave in the optical region.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Dalian University of Technology, 116024 China (P.R.C) 116024.

ABSTRACT
Control of the polarization of light is highly desirable for detection of material's chirality since biomolecules have vibrational modes in the optical region. Here, we report an ultrafast tuning of pronounced circular conversion dichroism (CCD) in the mid-infrared (M-IR) region, using an achiral phase change metamaterial (PCMM). Our structure consists of an array of Au squares separated from a continuous Au film by a phase change material (Ge2Sb2Te5) dielectric layer, where the Au square patches occupy the sites of a rectangular lattice. The extrinsically giant 2D chirality appears provided that the rectangular array of the Au squares is illuminated at an oblique incidence, and accomplishes a wide tunable wavelength range between 2664 and 3912 nm in the M-IR regime by switching between the amorphous and crystalline states of the Ge2Sb2Te5. A photothermal model is investigated to study the temporal variation of the temperature of the Ge2Sb2Te5 layer, and shows the advantage of fast transiting the phase of Ge2Sb2Te5 of 3.2 ns under an ultralow incident light intensity of 1.9 μW/μm(2). Our design is straightforward to fabricate and will be a promising candidate for controlling electromagnetic (EM) wave in the optical region.

No MeSH data available.


Related in: MedlinePlus