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Switchable Ultrathin Quarter-wave Plate in Terahertz Using Active Phase-change Metasurface.

Wang D, Zhang L, Gu Y, Mehmood MQ, Gong Y, Srivastava A, Jian L, Venkatesan T, Qiu CW, Hong M - Sci Rep (2015)

Bottom Line: In this work, we demonstrate a switchable ultrathin terahertz quarter-wave plate by hybridizing a phase change material, vanadium dioxide (VO2), with a metasurface.After the transition to metal phase, the quarter-wave plate operates at 0.502 THz.At the corresponding operating frequencies, the metasurface converts a linearly polarized light into a circularly polarized light.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, 117576, Singapore.

ABSTRACT
Metamaterials open up various exotic means to control electromagnetic waves and among them polarization manipulations with metamaterials have attracted intense attention. As of today, static responses of resonators in metamaterials lead to a narrow-band and single-function operation. Extension of the working frequency relies on multilayer metamaterials or different unit cells, which hinder the development of ultra-compact optical systems. In this work, we demonstrate a switchable ultrathin terahertz quarter-wave plate by hybridizing a phase change material, vanadium dioxide (VO2), with a metasurface. Before the phase transition, VO2 behaves as a semiconductor and the metasurface operates as a quarter-wave plate at 0.468 THz. After the transition to metal phase, the quarter-wave plate operates at 0.502 THz. At the corresponding operating frequencies, the metasurface converts a linearly polarized light into a circularly polarized light. This work reveals the feasibility to realize tunable/active and extremely low-profile polarization manipulation devices in the terahertz regime through the incorporation of such phase-change metasurfaces, enabling novel applications of ultrathin terahertz meta-devices.

No MeSH data available.


Related in: MedlinePlus

Performance of the switchable THz QWP.(a) Measured transmission spectra along two slots at 300 K (solid line) and 400 K (dot line). (b) Measured phase difference between y- and x-axes at 300 K (solid line) and 400 K (dot line). The inserted triangle indicates at 300 K, the transmission coefficients along two axes are the same, while their phase difference is close to 90°. The marked cross presents similar results at 400 K. (c) Numerically simulated transmission spectra with the corresponding phase delay (d) based on different measured VO2 electrical conductivities. (e) Analytical fitted transmission spectra and (f) the corresponding phase delays.
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f2: Performance of the switchable THz QWP.(a) Measured transmission spectra along two slots at 300 K (solid line) and 400 K (dot line). (b) Measured phase difference between y- and x-axes at 300 K (solid line) and 400 K (dot line). The inserted triangle indicates at 300 K, the transmission coefficients along two axes are the same, while their phase difference is close to 90°. The marked cross presents similar results at 400 K. (c) Numerically simulated transmission spectra with the corresponding phase delay (d) based on different measured VO2 electrical conductivities. (e) Analytical fitted transmission spectra and (f) the corresponding phase delays.

Mentions: Figure 2a,b show the measured transmission coefficients and phase delays of THz QWP before and after the VO2 phase transition. At 300 K, the QWP presents a transmission coefficient of 0.59 at 0.468 THz and a phase delay of 80° between y- and x-axes. This means the incident linearly polarized THz wave is converted into a circularly polarized wave. When the QWP is heated to 400 K, the VO2 phase transition changes the performance of the QWP. As it can be seen, a transmission coefficient of 0.28 at 0.502 THz and a phase delay of 75° between y- and x-axes are obtained. Therefore, the THz QWP is able to switch its operating frequency with a switching range of 34 GHz. The numerical simulation and analytical model fitting results are shown in Fig. 2c–f, which will be discussed in the simulation and analytical modeling sections. The experimental phase delays at both 300 and 400 K are smaller than 90°, indicating that the output THz wave is not a perfect circularly polarized light. This is due to the size fluctuation in the fabrication process and the damping effect in the fabricated samples. To experimentally compensate the phase difference and obtain a perfect circularly polarized output THz wave, the optimized phase delay in the simulation should be larger than 90°.


Switchable Ultrathin Quarter-wave Plate in Terahertz Using Active Phase-change Metasurface.

Wang D, Zhang L, Gu Y, Mehmood MQ, Gong Y, Srivastava A, Jian L, Venkatesan T, Qiu CW, Hong M - Sci Rep (2015)

Performance of the switchable THz QWP.(a) Measured transmission spectra along two slots at 300 K (solid line) and 400 K (dot line). (b) Measured phase difference between y- and x-axes at 300 K (solid line) and 400 K (dot line). The inserted triangle indicates at 300 K, the transmission coefficients along two axes are the same, while their phase difference is close to 90°. The marked cross presents similar results at 400 K. (c) Numerically simulated transmission spectra with the corresponding phase delay (d) based on different measured VO2 electrical conductivities. (e) Analytical fitted transmission spectra and (f) the corresponding phase delays.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4595731&req=5

f2: Performance of the switchable THz QWP.(a) Measured transmission spectra along two slots at 300 K (solid line) and 400 K (dot line). (b) Measured phase difference between y- and x-axes at 300 K (solid line) and 400 K (dot line). The inserted triangle indicates at 300 K, the transmission coefficients along two axes are the same, while their phase difference is close to 90°. The marked cross presents similar results at 400 K. (c) Numerically simulated transmission spectra with the corresponding phase delay (d) based on different measured VO2 electrical conductivities. (e) Analytical fitted transmission spectra and (f) the corresponding phase delays.
Mentions: Figure 2a,b show the measured transmission coefficients and phase delays of THz QWP before and after the VO2 phase transition. At 300 K, the QWP presents a transmission coefficient of 0.59 at 0.468 THz and a phase delay of 80° between y- and x-axes. This means the incident linearly polarized THz wave is converted into a circularly polarized wave. When the QWP is heated to 400 K, the VO2 phase transition changes the performance of the QWP. As it can be seen, a transmission coefficient of 0.28 at 0.502 THz and a phase delay of 75° between y- and x-axes are obtained. Therefore, the THz QWP is able to switch its operating frequency with a switching range of 34 GHz. The numerical simulation and analytical model fitting results are shown in Fig. 2c–f, which will be discussed in the simulation and analytical modeling sections. The experimental phase delays at both 300 and 400 K are smaller than 90°, indicating that the output THz wave is not a perfect circularly polarized light. This is due to the size fluctuation in the fabrication process and the damping effect in the fabricated samples. To experimentally compensate the phase difference and obtain a perfect circularly polarized output THz wave, the optimized phase delay in the simulation should be larger than 90°.

Bottom Line: In this work, we demonstrate a switchable ultrathin terahertz quarter-wave plate by hybridizing a phase change material, vanadium dioxide (VO2), with a metasurface.After the transition to metal phase, the quarter-wave plate operates at 0.502 THz.At the corresponding operating frequencies, the metasurface converts a linearly polarized light into a circularly polarized light.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, 117576, Singapore.

ABSTRACT
Metamaterials open up various exotic means to control electromagnetic waves and among them polarization manipulations with metamaterials have attracted intense attention. As of today, static responses of resonators in metamaterials lead to a narrow-band and single-function operation. Extension of the working frequency relies on multilayer metamaterials or different unit cells, which hinder the development of ultra-compact optical systems. In this work, we demonstrate a switchable ultrathin terahertz quarter-wave plate by hybridizing a phase change material, vanadium dioxide (VO2), with a metasurface. Before the phase transition, VO2 behaves as a semiconductor and the metasurface operates as a quarter-wave plate at 0.468 THz. After the transition to metal phase, the quarter-wave plate operates at 0.502 THz. At the corresponding operating frequencies, the metasurface converts a linearly polarized light into a circularly polarized light. This work reveals the feasibility to realize tunable/active and extremely low-profile polarization manipulation devices in the terahertz regime through the incorporation of such phase-change metasurfaces, enabling novel applications of ultrathin terahertz meta-devices.

No MeSH data available.


Related in: MedlinePlus