Infrared Absorption of Laser Patterned Sapphire Al<sub>2</sub>O<sub>3</sub> 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 <inline-formula><math xmlns="http://www.w3.org/199...
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2025-04-01
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| Online Access: | https://www.mdpi.com/2072-666X/16/4/476 |
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| author | Nan Zheng Daniel Smith Soon Hock Ng Hsin-Hui Huang Dominyka Stonytė Dominique Appadoo Jitraporn Vongsvivut Tomas Katkus Nguyen Hoai An Le Haoran Mu Yoshiaki Nishijima Lina Grineviciute Saulius Juodkazis |
| author_facet | Nan Zheng Daniel Smith Soon Hock Ng Hsin-Hui Huang Dominyka Stonytė Dominique Appadoo Jitraporn Vongsvivut Tomas Katkus Nguyen Hoai An Le Haoran Mu Yoshiaki Nishijima Lina Grineviciute Saulius Juodkazis |
| author_sort | Nan Zheng |
| collection | DOAJ |
| description | 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 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>∝</mo><mo>(</mo><mn>1</mn><mo>−</mo><mi>R</mi><mo>)</mo></mrow></semantics></math></inline-formula> 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 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>∝</mo><mo form="prefix">cos</mo><msub><mi>θ</mi><mi>a</mi></msub></mrow></semantics></math></inline-formula> 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. |
| format | Article |
| id | doaj-art-efb4aba5d5144c96ab82862a11d4200f |
| institution | OA Journals |
| issn | 2072-666X |
| language | English |
| publishDate | 2025-04-01 |
| publisher | MDPI AG |
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| series | Micromachines |
| spelling | doaj-art-efb4aba5d5144c96ab82862a11d4200f2025-08-20T02:18:10ZengMDPI AGMicromachines2072-666X2025-04-0116447610.3390/mi16040476Infrared Absorption of Laser Patterned Sapphire Al<sub>2</sub>O<sub>3</sub> for Radiative CoolingNan Zheng0Daniel Smith1Soon Hock Ng2Hsin-Hui Huang3Dominyka Stonytė4Dominique Appadoo5Jitraporn Vongsvivut6Tomas Katkus7Nguyen Hoai An Le8Haoran Mu9Yoshiaki Nishijima10Lina Grineviciute11Saulius Juodkazis12Optical Sciences Centre and ARC Training Centre in Surface Engineering for Advanced Materials (SEAM), School of Science, Swinburne University of Technology, Hawthorn, VIC 3122, AustraliaOptical Sciences Centre and ARC Training Centre in Surface Engineering for Advanced Materials (SEAM), School of Science, Swinburne University of Technology, Hawthorn, VIC 3122, AustraliaOptical Sciences Centre and ARC Training Centre in Surface Engineering for Advanced Materials (SEAM), School of Science, Swinburne University of Technology, Hawthorn, VIC 3122, AustraliaOptical Sciences Centre and ARC Training Centre in Surface Engineering for Advanced Materials (SEAM), School of Science, Swinburne University of Technology, Hawthorn, VIC 3122, AustraliaLaser Research Centre, Physics Faculty, Vilnius University, Saulėtekio Ave. 10, LT-10223 Vilnius, LithuaniaTHz Beamline, ANSTO-Australian Synchrotron, 800 Blackburn Rd, Clayton, VIC 3168, AustraliaInfrared Microspectroscopy (IRM) Beamline, ANSTO-Australian Synchrotron, 800 Blackburn Rd, Clayton, VIC 3168, AustraliaOptical Sciences Centre and ARC Training Centre in Surface Engineering for Advanced Materials (SEAM), School of Science, Swinburne University of Technology, Hawthorn, VIC 3122, AustraliaOptical Sciences Centre and ARC Training Centre in Surface Engineering for Advanced Materials (SEAM), School of Science, Swinburne University of Technology, Hawthorn, VIC 3122, AustraliaOptical Sciences Centre and ARC Training Centre in Surface Engineering for Advanced Materials (SEAM), School of Science, Swinburne University of Technology, Hawthorn, VIC 3122, AustraliaDepartment of Electrical and Computer Engineering, Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Kanagawa, JapanCenter for Physical Sciences and Technology (FTMC), Savanoriu Ave. 231, LT-02300 Vilnius, LithuaniaOptical Sciences Centre and ARC Training Centre in Surface Engineering for Advanced Materials (SEAM), School of Science, Swinburne University of Technology, Hawthorn, VIC 3122, AustraliaThe 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 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>∝</mo><mo>(</mo><mn>1</mn><mo>−</mo><mi>R</mi><mo>)</mo></mrow></semantics></math></inline-formula> 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 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>∝</mo><mo form="prefix">cos</mo><msub><mi>θ</mi><mi>a</mi></msub></mrow></semantics></math></inline-formula> 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.https://www.mdpi.com/2072-666X/16/4/476femtosecond laser ablationdirect energy depositionradiative coolinganti-reflective surfaces |
| spellingShingle | Nan Zheng Daniel Smith Soon Hock Ng Hsin-Hui Huang Dominyka Stonytė Dominique Appadoo Jitraporn Vongsvivut Tomas Katkus Nguyen Hoai An Le Haoran Mu Yoshiaki Nishijima Lina Grineviciute Saulius Juodkazis Infrared Absorption of Laser Patterned Sapphire Al<sub>2</sub>O<sub>3</sub> for Radiative Cooling Micromachines femtosecond laser ablation direct energy deposition radiative cooling anti-reflective surfaces |
| title | Infrared Absorption of Laser Patterned Sapphire Al<sub>2</sub>O<sub>3</sub> for Radiative Cooling |
| title_full | Infrared Absorption of Laser Patterned Sapphire Al<sub>2</sub>O<sub>3</sub> for Radiative Cooling |
| title_fullStr | Infrared Absorption of Laser Patterned Sapphire Al<sub>2</sub>O<sub>3</sub> for Radiative Cooling |
| title_full_unstemmed | Infrared Absorption of Laser Patterned Sapphire Al<sub>2</sub>O<sub>3</sub> for Radiative Cooling |
| title_short | Infrared Absorption of Laser Patterned Sapphire Al<sub>2</sub>O<sub>3</sub> for Radiative Cooling |
| title_sort | infrared absorption of laser patterned sapphire al sub 2 sub o sub 3 sub for radiative cooling |
| topic | femtosecond laser ablation direct energy deposition radiative cooling anti-reflective surfaces |
| url | https://www.mdpi.com/2072-666X/16/4/476 |
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