Low-power design of electrotunable color filters and optical switches

Chowdhary, Ashish Kumar; Sikdar, Debabrata

doi:10.1364/josab.408502

Cited by 14 publications

(5 citation statements)

References 41 publications

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“…DAST, an EO polymer having tunability near-VIS regime and possessing a very large EO coefficient (3.41 nm V −1 ) was reported by Geis et al [50]. The refractive index of DAST as function of the applied voltage is defined as [29]:…”

Section: Static Vs Electro-tunable Windowsmentioning

confidence: 98%

“…For example, for fabricating SiO 2 -Ag-SiO 2 based static window design, first, we need to take a one-side polished glass substrate made of silica typically 5 mm thick. Then silver metal needs to be deposited on top of silica using electron beam (e-beam) evaporation technique [29,[59][60][61]. Again 65 nm thick silica needs to be deposited on the top of Ag-SiO 2 stack using spin coating or e-beam evaporation technique.…”

Section: Prospective Fabrication Techniquementioning

confidence: 99%

“…For static windows, we make use of different dielectrics [silica (SiO 2 ), titanium oxide (TiO 2 ), and silicon (Si)] as the top and bottom insulator layers. For electro-tunable windows, we make use of an electro-optic (EO) polymer: 4-dimethyl-amino-Nmethyl-4-stilbazoliumtosylate (DAST), as the insulator layers, to dynamically control the portions of transmitted solar radiation over a voltage range of −12 to +12 V [29]. After finding suitable choice of materials for IMI thin-films, we optimize the thickness of each layer in our design to operate in different modes based on climatic condition.…”

Section: Introductionmentioning

confidence: 99%

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Multilayer thin-film based nanophotonic windows: static versus electrotunable design

Chowdhary¹,

Sikdar²

2021

J. Opt.

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To meet the global energy demand, rapid growth in fossil fuel consumption has significantly contributed to global warming. Judicious utilization of renewable energy resources could help to combat this global challenge. Here, we present a comparative study on the designs of static and electro-tunable ‘smart’ windows that could help to reduce the energy need of typical airconditioning systems deployed in buildings and motor vehicles. Our design comprises insulator–metal–insulator multi-layered thin-films deposited over a silica glass substrate to filter visible and infrared solar radiation selectively. For static windows, we optimize our design to operate in diverse climatic conditions by choosing different combinations and thicknesses of metal and insulator layers. Whereas for electro-tunable windows, we use an electro–optic polymer as the insulator layers to dynamically control portions of transmitted solar radiation over a voltage range of −12 V to +12 V. Through size-dependence analysis, we could safely assume that the performance of smart windows is less likely to degrade during experimental realization. Our designs are lithography-free, large-area compatible, polarization-independent, angle-insensitive, and robust to fabrication imperfections. The analytical results show a near-perfect match with the simulation findings. The theoretically calculated figure of merit indicates that our proposed smart windows can outperform industry-standard commercial windows.

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Section: Static Vs Electro-tunable Windowsmentioning

confidence: 98%

Section: Prospective Fabrication Techniquementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Multilayer thin-film based nanophotonic windows: static versus electrotunable design

Chowdhary¹,

Sikdar²

2021

J. Opt.

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“…Based on the above understanding, we theoretically calculated the absorption characteristics of graphene-air homogenized medium and compared those with the numerically computed absorption response of free-standing nanoribbons for different Fermi energies. We use the TMM to evaluate the absorption response by assuming the homogenized medium as linear and non-magnetic [46,47]. The solid and dashed lines in figure 2(d) indicate numerically and theoretically calculated absorption spectra, respectively.…”

Section: Role Of Gnrs and Dielectric Spacer In Terahertz Broadband Ab...mentioning

confidence: 99%

Tunable terahertz absorption modulation in graphene nanoribbon-assisted dielectric metamaterial

Dhriti¹,

Chowdhary²,

Chouhan³

et al. 2022

J. Phys. D: Appl. Phys.

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Designing metamaterial absorbers with tunable and broadband response with high modulation depth is crucial for application in switches, polarization sensitive devices, and optical filters. In this article, we report a tunable broadband metamaterial absorber in terahertz regime. The design comprises frustum shaped dielectric (SiO2) metamaterial structures on top of a one-dimensional period array of graphene nanoribbons deposited over the ultrathin metal-backed dielectric. For TM polarization, our design offers a near-perfect absorption in the range of 0.72 THz to 0.9 THz with 72.7 % fractional bandwidth. On the contrary, we get a negligible absorption for the TE polarization of the incident light, thereby giving an absorption contrast ratio up to 20.5 dB. The excitation of plasmons in graphene nanoribbons combined with resonance induced by the graphene-dielectric-metal cavity leads to nearly perfect broadband absorption for the TM polarized radiation. Further, modulation of the absorption spectrum has been achieved by changing graphene conductivity with the help of its Fermi energy. A theoretical model based on effective medium theory and transfer matrix method has been presented to validate absorption response for various Fermi energy values of the graphene. The figure of merit of our design can outperform some of the recently reported tunable metamaterial absorbers.

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“…The numerical results are verified theoretically using transfer matrix method (TMM) implemented using MATLAB R2020b. While applying TMM, we assume the medium to be homogeneous, linear, and non-magnetic [34]. We consider a TM polarized plane wave incident normally on multilayered thin-film based PRC.…”

Section: Theoretical Verificationmentioning

confidence: 99%

Selective thermal emitters for high-performance all-day radiative cooling

Chowdhary

Reddy

Sikdar

2021

J. Phys. D: Appl. Phys.

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Passive radiative coolers (PRCs), which pump excess heat to cold exterior space via thermal radiation, have emerged as a promising energy-free technology in cooling buildings, thermal power plants, and photovoltaics. However, designing a ‘daytime’ PRC is challenging due to the simultaneous requirement of high reflectance in the solar spectral regime (0.3–2.5 µm) and high emissivity in the atmospheric transmittance window (8–13 µm). Here, we present a large-area compatible and lithography-free nanoscale multilayer design of daytime PRC based on two pairs of tandem silicon dioxide–aluminium nitride dielectric layer cascaded to a silver ground metal placed over a silicon substrate. We theoretically achieve near-perfect reflectance (97.3%) over the solar spectral regime while maintaining high emissivity (80%) in the atmospheric transmittance window. During the daytime under direct sunlight, the cooling power of the proposed structure is reported to be 115 W m − 2 with a temperature reduction up to 15 K below the ambient temperature, when the effect of convection and conductive heat transfer is considered. Our design is polarization-independent and angle-insensitive up to 70 degrees of angle of incidence. An excellent match between our theoretical and simulation results validates our findings. The fabrication tolerance study reveals that the cooling performance of our robust design is unlikely to degrade much during experimental realization. The figure of merit calculation indicates that our PRC can outperform recently reported daytime PRCs.

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Low-power design of electrotunable color filters and optical switches

Cited by 14 publications

References 41 publications

Multilayer thin-film based nanophotonic windows: static versus electrotunable design

Multilayer thin-film based nanophotonic windows: static versus electrotunable design

Tunable terahertz absorption modulation in graphene nanoribbon-assisted dielectric metamaterial

Selective thermal emitters for high-performance all-day radiative cooling

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