| Title |
Infrared absorption of laser patterned sapphire Al2O3 for radiative cooling / |
| Authors |
Zheng, Nan ; Smith, Daniel ; Ng, Soon Hock ; Huang, Hsin-Hui ; Stonytė, Dominyka ; Appadoo, Dominique ; Vongsvivut, Jitraporn ; Katkus, Tomas ; Le, Nguyen Hoai An ; Mu, Haoran ; Nishijima, Yoshiaki ; Grinevičiūtė, Lina ; Juodkazis, Saulius |
| DOI |
10.3390/mi16040476 |
| Full Text |
|
| Is Part of |
Micromachines.. Basel : MDPI. 2025, vol. 16, iss. 4, art. no. 476, p. [1-17].. eISSN 2072-666X |
| Keywords [eng] |
femtosecond laser ablation ; direct energy deposition ; radiative cooling ; anti-reflective surfaces |
| Abstract [eng] |
The reflectance (R) of linear and circular micro-gratings on c-plane sapphire Al2O3 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. |
| Published |
Basel : MDPI |
| Type |
Journal article |
| Language |
English |
| Publication date |
2025 |
| CC license |
|
