Picosecond Laser Ablation of Millimeter-Wave Subwavelength Structures on Alumina and Sapphire
| Autor: | Jürgen Koch, Ryota Takaku, Shaul Hanany, Tomotake Matsumura, Elena Fadeeva, Qi Wen, Karl Young |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Materials science
medicine.medical_treatment FOS: Physical sciences Applied Physics (physics.app-ph) 02 engineering and technology 01 natural sciences Fluence law.invention 010309 optics law 0103 physical sciences medicine Laser power scaling Electrical and Electronic Engineering Instrumentation and Methods for Astrophysics (astro-ph.IM) Attenuation length Pulse duration Physics - Applied Physics 021001 nanoscience & nanotechnology Laser Ablation Atomic and Molecular Physics and Optics Electronic Optical and Magnetic Materials Extremely high frequency Sapphire Atomic physics 0210 nano-technology Astrophysics - Instrumentation and Methods for Astrophysics Optics (physics.optics) Physics - Optics |
| Popis: | We use a 1030 nm laser with 7 ps pulse duration and average power up to 100 W to ablate pyramid-shape subwavelength structures (SWS) on alumina and sapphire. The SWS give an effective and cryogenically robust anti-reflection coating in the millimeter-wave band. We demonstrate average ablation rate of up to 34 mm$^3$/min and 20 mm$^3$/min for structure heights of 900 $\mu$m and 750 $\mu$m on alumina and sapphire, respectively. These rates are a factor of 34 and 9 higher than reported previously on similar structures. We propose a model that relates structure height to cumulative laser fluence. The model depends on the absorption length $\delta$, which is assumed to depend on peak fluence, and on the threshold fluence $\phi_{th}$. Using a best-fit procedure we find an average $\delta = 630$ nm and 650 nm, and $\phi_{th} = 2.0^{+0.5}_{-0.5}$ J/cm$^2$ and $2.3^{+0.1}_{-0.1}$ J/cm$^2$ for alumina and sapphire, respectively, for peak fluence values between 30 and 70 J/cm$^{2}$. With the best fit values, the model and data values for cumulative fluence agree to within 10%. Given inputs for $\delta$ and $\phi_{th}$ the model is used to predict average ablation rates as a function of SWS height and average laser power. Comment: 15 pages, 11 figures, submitted to Optics & Laser Technology |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|