Infrared Absorption of Laser Patterned Sapphire Al2O3 for Radiative Cooling
The reflectance (<i>R</i>) of linear and circular micro-gratings on c-plane sapphire Al<sub>2</sub>O<sub>3</sub> ablated by a femtosecond (fs) laser were spectrally characterised for thermal emission ∝(1-R) in the mid-to-far infrared (IR) spectral range. An IR camera was used to determine the blackbody radiation temperature from laser-patterned regions, which showed (3-6)% larger emissivity dependent on the grating pattern. The azimuthal emission curve closely followed the Lambertian angular profile ∝cosθa at the 7.5-13 μm emission band. The back-side ablation method on transparent substrates was employed to prevent debris formation during energy deposition as it applies a forward pressure of >0.3 GPa to the debris and molten skin layer. The back-side ablation maximises energy deposition at the exit interface where the transition occurs from the high-to-low refractive index. Phononic absorption in the Reststrahlen region 20-30 μm can be tailored with the fs laser inscription of sensor structures/gratings.
Authors
- Hsin‐Hui Huang (ORCID: https://orcid.org/0000-0001-6279-2291)
- Soon Hock Ng (ORCID: https://orcid.org/0000-0002-9164-3399)
- Jitraporn Vongsvivut (ORCID: https://orcid.org/0000-0003-0699-3464)
- Saulius Juodkazis (ORCID: https://orcid.org/0000-0003-3542-3874)
- Lina Grinevičiūtė (ORCID: https://orcid.org/0000-0001-8505-5067)
- Nguyen Hoai An Le (ORCID: https://orcid.org/0009-0008-4627-4978)
- Dominique Appadoo (ORCID: https://orcid.org/0000-0001-6263-8665)
- Dominyka Stonytė (ORCID: https://orcid.org/0009-0005-3784-9520)
- Tomas A. Katkus (ORCID: https://orcid.org/0000-0001-5496-046X)
- Yoshiaki Nishijima (ORCID: https://orcid.org/0000-0003-0650-4536)
- Daniel Smith (ORCID: https://orcid.org/0000-0002-2543-5209)
- Haoran Mu (ORCID: https://orcid.org/0000-0001-6561-6293)
- Nan Zheng (ORCID: https://orcid.org/0009-0003-4378-8088)
Institutions
- Australian Nuclear Science and Technology Organisation (AU)
- Vilnius University (LT)
- Yokohama National University (JP)
- Australian Synchrotron (AU)
- Japan Science and Technology Agency (JP)
- Center for Physical Sciences and Technology (LT)
- Swinburne University of Technology (AU)
Publication Details
- Journal
- Micromachines
- Published
- 2025-04-16
- DOI
- https://doi.org/10.3390/mi16040476
- Citations
- 3
- Primary Topic
- Thermal Radiation and Cooling Technologies
- Type
- article
- Field-Weighted Citation Impact
- 2.86
Funders
- Discovery Eye Foundation
- Australian Nuclear Science and Technology Organisation
- Australian Synchrotron
- Swinburne University of Technology
- Japan Science and Technology Agency
- Precursory Research for Embryonic Science and Technology