Reversible switching of electromagnetically induced transparency in phase change metasurfaces

Libang Mao; Yang Li; Guixin Li; Shuang Zhang; Tun Cao

doi:10.1117/1.AP.2.5.056004

Journals >Advanced Photonics >Volume 2 >Issue 5 >Page 056004 > Article

Advanced Photonics
Vol. 2, Issue 5, 056004 (2020)

Reversible switching of electromagnetically induced transparency in phase change metasurfaces

Libang Mao^1、†, Yang Li^1、2, Guixin Li², Shuang Zhang³, and Tun Cao^1、*

Author Affiliations

¹Dalian University of Technology, School of Optoelectronic Engineering and Instrumentation Science, Dalian, China

²Southern University of Science and Technology, Department of Materials Science and Engineering, Shenzhen, China

³University of Birmingham, School of Physics and Astronomy, Birmingham, United Kingdom

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DOI: 10.1117/1.AP.2.5.056004 Cite this Article Set citation alerts

Libang Mao, Yang Li, Guixin Li, Shuang Zhang, Tun Cao. Reversible switching of electromagnetically induced transparency in phase change metasurfaces[J]. Advanced Photonics, 2020, 2(5): 056004 Copy Citation Text

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Configuration of the EIT metasurface. (a) Schematic of the all-optical, nonvolatile, chalcogenide metamaterial induced EIT switch: single ns laser pulse transits a 35-nm-thick GST225 film, backward and forward between AM and CR on an area covering 510,000 antennae. (b) A representation of the resonator. The geometrical parameters are: l1=380 nm, l2=550 nm, w=220 nm, d=120 nm, and p=700 nm, respectively; the thicknesses of the top Au resonator and GST225 dielectric layer are TAu=35 nm and TGST=35 nm, respectively. The SEM images of the 5×7 resonators section of the fabricated metasurface (c) before crystallizing and (d) after crystallizing the GST225 dielectric film hybridized with the metasurface. Scale bar: 2 μm.

Fig. 1. Configuration of the EIT metasurface. (a) Schematic of the all-optical, nonvolatile, chalcogenide metamaterial induced EIT switch: single ns laser pulse transits a 35-nm-thick GST225 film, backward and forward between AM and CR on an area covering 510,000 antennae. (b) A representation of the resonator. The geometrical parameters are:

l_{1} = 380 nm

l_{2} = 550 nm

w = 220 nm

d = 120 nm

, and

p = 700 nm

, respectively; the thicknesses of the top Au resonator and GST225 dielectric layer are

T_{Au} = 35 nm

and

T_{GST} = 35 nm

, respectively. The SEM images of the

5 \times 7

resonators section of the fabricated metasurface (c) before crystallizing and (d) after crystallizing the GST225 dielectric film hybridized with the metasurface. Scale bar:

2 μ m

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$Sequential treatment for the reversible phase transition. (a) Scheme of the reversible phase transition of the GST225 film hybridized with an EIT metasurface: AD-AM GST225 is first annealed above 180°C to change to CR GST225 using a hot plate. A single ns laser pulse (5 ns, 24 mJ/cm2) is triggered to heat the CR GST225 film above 600°C that re-amorphizes the CR GST225. Subsequent quenching results in the MQ-AM GST225. To recrystallise the MQ-AM GST225, for which a temperature above 180°C but below 600°C is required, a single-ns laser pulse with a lower energy (5 ns, 14 mJ/cm2) is taken. (b) Visible–NIR complex refractive index of 35-nm-thick GST225 film at the structural states of the AD-AM (red line), CR (blue line), MQ-AM (orange line), and R-CR (green line), where the refractive index is measured using an ellipsometer over a spectral range of 1000 to 2400 nm.$

Fig. 2. Sequential treatment for the reversible phase transition. (a) Scheme of the reversible phase transition of the GST225 film hybridized with an EIT metasurface: AD-AM GST225 is first annealed above 180°C to change to CR GST225 using a hot plate. A single ns laser pulse (5 ns,

24 mJ / {cm}^{2}

) is triggered to heat the CR GST225 film above 600°C that re-amorphizes the CR GST225. Subsequent quenching results in the MQ-AM GST225. To recrystallise the MQ-AM GST225, for which a temperature above 180°C but below 600°C is required, a single-ns laser pulse with a lower energy (5 ns,

14 mJ / {cm}^{2}

) is taken. (b) Visible–NIR complex refractive index of 35-nm-thick GST225 film at the structural states of the AD-AM (red line), CR (blue line), MQ-AM (orange line), and R-CR (green line), where the refractive index is measured using an ellipsometer over a spectral range of 1000 to 2400 nm.

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Fig. 3. Experimental realization of reversibly tunable EIT and the comparison with theory and simulation. (a) The FTIR measurement of the normalized transmittance spectra, (b) theoretical fitted transmittance spectra, and (c) numerical simulated transmittance spectra of the phase change metasurface with the different structural states of AD-AM, CR, MQ-AM, and R-CR.

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Fig. 4. Bright and dark modes in EIT. The FDTD simulated spectra and

E

-field distributions for (a) the VCW resonators array with the AM-GST225 film at

λ = 2021 nm

, (b) the HCW resonators array with the AM-GST225 film at

λ = 1565 nm

, (c) the metasurface with the AM-GST225 film at

λ = 1811 nm

, and (d) the metasurface with the CR-GST225 film at

λ = 2161 nm

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Fig. 5. The

n_{g}

for the different structural states of the GST225.

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Fig. 6. (a)–(c) Measured transmittance spectra of the phase change metasurface for 30 switching times. (d) The values of resonance peaks for AM (indicated by red dots) and CR (indicated by blue dots) states with 30 transition times.

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Libang Mao, Yang Li, Guixin Li, Shuang Zhang, Tun Cao. Reversible switching of electromagnetically induced transparency in phase change metasurfaces[J]. Advanced Photonics, 2020, 2(5): 056004

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