Dynamic optical response of SU-8 upon UV treatment

Ghanekar, Alok; Ricci, Margaret Speed; Tian, Yanpei; Gregory, Otto J.; Zheng, Yi

doi:10.1364/ome.8.002017

Cited by 9 publications

(9 citation statements)

References 20 publications

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“…In principle, the easiest way to compensate for the emissivity loss is to use thicker polymer films; however, this inevitably broadens the emission spectrum ( fig. S2) (9,12,(27)(28)(29)(30)(31)(32). In contrast, the induced sSPP resonance in the JET can realize near-ideal selective emission even with an extremely thin layer of PDMS (4 m).…”

Section: Resultsmentioning

confidence: 99%

A Janus emitter for passive heat release from enclosures

et al. 2020

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Passive radiative cooling functions by reflecting the solar spectrum and emitting infrared waves in broadband or selectively. However, cooling enclosed spaces that trap heat by greenhouse effect remains a challenge. We present a Janus emitter (JET) consisting of an Ag–polydimethylsiloxane layer on micropatterned quartz substrate. The induced spoof surface plasmon polariton helps overcome inherent emissivity loss of the polymer and creates near-ideal selective and broadband emission on the separate sides. This design results in not only remarkable surface cooling when the JET is attached with either side facing outwards but also space cooling when used as an enclosure wall. Thus, the JET can passively mitigate the greenhouse effect in enclosures while offering surface cooling performance comparable to conventional radiative coolers.

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Section: Resultsmentioning

confidence: 99%

A Janus emitter for passive heat release from enclosures

et al. 2020

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“…The similar reflectance drops are observered from 2 µm to 2.6 µm when thermal annealing temperature increases. A literature has been recently published about how to extract the dielectric function of SU-8 polymer from the reflectance spectra of SU-8 [43]. The same approach is employed to obtain the dielectric function of the nano-composites in this work.…”

Section: High Temperature Stability Resultsmentioning

confidence: 99%

“…The artificial thermal metamaterials which have selective high emissivity at narrowband or broadband wavelength range show promising potentials in the advanced engineering applications, such as thermophotovoltaics (TPVs), infrared thermal sensing [1][2][3][4][5][6][7][8], thermal diodes [9][10][11][12], radiation cooling [13][14][15][16], thermal rectification [17][18][19]43], biosensors, and chemical sensors [20,21]. Some materials, such as rare earth doped ceramics, possess selective high emissivity, but they do not show sufficient wavelength selectivity that are suitable for the emerging engineering applications [22].…”

Section: Introductionmentioning

confidence: 99%

Near-infrared optics of nanoparticles embedded silica thin films

et al. 2019

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This work investigates experimentally the near-infrared optical properties of SiO 2 thin film embedded with tungsten (W) nanoparticles at varying volume fractions. The samples are prepared by using the technique of magnetron sputtering. The formation and distribution of W nanoparticles are characterized using transmission electron microscopy, and the volume fraction of W nanoparticles is validated by Auger electron spectroscopy. Near-and mid-infrared diffuse reflectance measurements are conducted using Fourier transform infrared spectroscopy. The samples exhibit wavelength selective optical response in the near-infrared region and are suitable for applications involving selective thermal emitters/absorbers. Measured reflectance data is utilized to estimate the effective dielectric function of the nano-composites. Calculated reflectance spectra in different samples are compared to the measured spectra using the experimentally measured dielectric function of these samples in the near-infrared region. Reflectance spectra after thermal annealing at different temperature are compared to show how the thermal treatment affects the optical properties of samples. Optimized structures are proposed for thermal emitters and absorbers with different volume fractions of W nanoparticles.

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“…These characterizations are used to estimate an average particle size of the graphite of 660 nm. In addition, the complex refractive index of the graphite is determined by assuming a Lorentz–Drude form of its dielectric function and using the reflectance spectrum to calculate Lorentz–Drude parameters, as is exemplified in the literature [ 38 ]. Based upon the resulting efficiencies, the somewhat strong scattering properties of the graphite are expected to have a negative impact on the absorptance of the structure when the piston is lowered.…”

Section: Methodsmentioning

confidence: 99%

Piston-Type Optical Modulator for Dynamic Thermal Radiation Tuning Applications

Caratenuto

Zheng

2021

Materials

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This study introduces a movable piston-like structure that provides a simple and cost-effective avenue for dynamically tuning thermal radiation. This structure leverages two materials with dissimilar optical responses—graphite and aluminum—to modulate from a state of high reflectance to a state of high absorptance. A cavity is created in the graphite to house an aluminum cylinder, which is displaced to actuate the device. In its raised state, the large aluminum surface area promotes a highly reflective response, while in its lowered state, the expanded graphite surface area and blackbody cavity-like interactions significantly enhance absorptance. By optimizing the area ratio, reflectance tunability of over 30% is achieved for nearly the entire ultraviolet, visible, and near-infrared wavelength regions. Furthermore, a theoretical analysis postulates wavelength-dependent effectivenesses as high as 0.70 for this method, indicating that tunabilities approaching 70% can be achieved by exploiting near-ideal absorbers and reflectors. The analog nature of this control method allows for an infinitely variable optical response between the upper and lower bounds of the device. These valuable characteristics would enable this material structure to serve practical applications, such as reducing cost and energy requirements for environmental temperature management operations.

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Dynamic optical response of SU-8 upon UV treatment

Cited by 9 publications

References 20 publications

A Janus emitter for passive heat release from enclosures

A Janus emitter for passive heat release from enclosures

Near-infrared optics of nanoparticles embedded silica thin films

Piston-Type Optical Modulator for Dynamic Thermal Radiation Tuning Applications

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