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Repeated disordered structure for radiative cooling application via scalable stamping method from designed CaCO3 templates
(2026-07-01)
Kaewmanee, Taweesak
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Sakata, Patawee
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Gridtayawong, Pharit
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Rueangsawang, Worawut
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Ponghiransmith, Chattrarat
Radiative cooling via micro-patterned surfaces provides energy-efficient solution for thermal regulation by enhancing selective thermal emission within the atmospheric transparency window (8–13 μm). This study investigates the effects of microstructural patterning through a low-cost and scalable stamping technique. The patterning templates were uniquely produced by the removal of randomly-distributed CaCO<inf>3</inf> polymorphs—calcite and vaterite with specific sizes. The novel calcite-imprinted structures exhibit superior mid-infrared emissivity (>0.96) and maintain consistent temperature reduction across varying weather conditions, outperforming vaterite-based films. However, the cooling performance of unmodified patterns is limited by solar absorption. To address this, TiO<inf>2</inf> (rutile phase) is incorporated into a polymer matrix before being stamped to enhance solar reflectivity. Moreover, hydrophobic aerogels could be inserted between micropattern gaps to facilitate self-cleaning functionality. A composite film containing 3 wt% TiO<inf>2</inf> with the calcite micro-patterning and hydrophobic aerogel achieves a temperature drop of 4.8 °C, compared to 1.2 °C of pristine patterns relative to that of a clear film. For real-world applicability, the optimized patterning strategies were further validated on fiber cement rooftile surfaces, yielding best temperature reductions of 2.5 °C compared to pattern-free coating under a tropical climate. The calculated net cooling power of 3 wt% TiO<inf>2</inf> patterned film with aerogel is 26.9 W/m<sup>2</sup>. This novel passive-cooling stamping strategy is low-cost, scalable, and suitable for large-area deployment, reducing the energy burden of active cooling technologies.
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Investigation on optical integration between LED Mid-IR light sources and Si-based waveguides for sensing applications
(2022-01-07)
Jaturaphagorn, Pawaphat
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Chaisakul, Papichaya
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Chattham, Nattaporn
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Limsuwan, Pichet
Research on mid-IR silicon-based waveguides has recently received strong interest. Particularly, this paper focuses on one of the critical issues in micron-scale photonic integrated circuits, which is to efficiently couple a mid-IR LED (light emitting diode) light source to an external micron-scale waveguide. The optical coupling scheme is crucial for the exploitation of LED light sources in waveguide-based spectroscopic sensing applications. This paper reports optical coupling scheme between an LED mid-IR light source and a silicon rich silicon nitride (SiN) waveguide that could enable the use of LED-based light sources. Finally, the detection limit of the investigated device for carbon dioxide gas detection is calculated.
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Optimization of end-fire coupling between an LED mid-IR light source and SiNx optical waveguides for spectroscopic sensing
(2021-12-01)
Jaturaphagorn, Pawaphat
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Chattham, Nattaporn
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Limsuwan, Pichet
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Chaisakul, Papichaya
We design and optimize an optical coupling structure between a superluminescent light emitting diodes (SLED) and SiN<inf>x</inf> waveguides for the optical sensing, in which an efficient coupling between these waveguides is challenging due to significant cross-sectional difference. From FDTD investigation, we identify the coupling scheme that is suitable to directly couple light from a SLED into a relatively-thin SiN<inf>x</inf> waveguide suitable for optical sensing based on the evanescent field absorption. The coupling structure is systematically investigated and optimized in terms of refractive indices, coupler's geometrical parameters, and fabrication variations with corresponding detection performance. The coupling scheme could be instrumental in enabling the use of SLED technology in Si-based photonic integrated circuits for sensing applications.
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All-dielectric silicon metalens for two-dimensional particle manipulation in optical tweezers
(2020-09-01)
Chantakit, Teanchai
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Schlickriede, Christian
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Sain, Basudeb
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Meyer, Fabian
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Weiss, Thomas
Dynamic control of compact chip-scale contactless manipulation of particles for bioscience applications remains a challenging endeavor, which is restrained by the balance between trapping efficiency and scalable apparatus. Metasurfaces offer the implementation of feasible optical tweezers on a planar platform for shaping the exerted optical force by a microscale-integrated device. Here we design and experimentally demonstrate a highly efficient silicon-based metalens for two-dimensional optical trapping in the near-infrared. Our metalens concept is based on the Pancharatnam-Berry phase, which enables the device for polarization-sensitive particle manipulation. Our optical trapping setup is capable of adjusting the position of both the metasurface lens and the particle chamber freely in three directions, which offers great freedom for optical trap adjustment and alignment. Two-dimensional (2D) particle manipulation is done with a relatively low-numerical-aperture metalens (NA<inf>ML</inf> = 0.6). We experimentally demonstrate both 2D polarization-sensitive drag and drop manipulation of polystyrene particles suspended in water and transfer of angular orbital momentum to these particles with a single tailored beam. Our work may open new possibilities for lab-on-a-chip optical trapping for bioscience applications and microscale to nanoscale optical tweezers.

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