Picosecond laser ablation of millimeter-wave subwavelength structures on alumina and sapphire

Qi Wen; Elena Fadeeva; Shaul Hanany; Jürgen Koch; Tomotake Matsumura; Ryota Takaku; Karl Young

doi:10.1016/j.optlastec.2021.107207

Picosecond laser ablation of millimeter-wave subwavelength structures on alumina and sapphire

Qi Wen, Elena Fadeeva, Shaul Hanany, Jürgen Koch, Tomotake Matsumura, Ryota Takaku, Karl Young

Physics and Astronomy (Twin Cities)

Research output: Contribution to journal › Article › peer-review

7 Scopus citations

Abstract

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 mm³/min and 20 mm³/min for structure heights of 900 μm and 750 μm 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 δ, which is assumed to depend on peak fluence, and on the threshold fluence ϕ_th. Using a best-fit procedure we find an average δ=630 nm and 650 nm, and ϕ_th=2.0_-0.5^+0.5 J/cm² and 2.3_-0.1^+0.1 J/cm² for alumina and sapphire, respectively, for peak fluence values between 30 and 70 J/cm². With the best fit values, the model and data values for cumulative fluence agree to within 10%. Given inputs for δ and ϕ_th the model is used to predict average ablation rates as a function of SWS height and average laser power.

Original language	English (US)
Article number	107207
Journal	Optics and Laser Technology
Volume	142
DOIs	https://doi.org/10.1016/j.optlastec.2021.107207
State	Published - Oct 2021

Bibliographical note

Funding Information:
We acknowledge support provided by Trumpf GmbH & Co. KG (Ditzingen, Germany); the laser machining trials reported here were done at their laser application center. We thank Christopher Geach for helpful discussions. TM was supported by World Premier International Research Center Initiative (WPI), MEXT, Japan. This work was supported by JSPS KAKENHI Grant Number 18KK0083.

Funding Information:
We acknowledge support provided by Trumpf GmbH & Co. KG (Ditzingen, Germany); the laser machining trials reported here were done at their laser application center. We thank Christopher Geach for helpful discussions. TM was supported by World Premier International Research Center Initiative (WPI), MEXT, Japan. This work was supported by JSPS KAKENHI Grant Number 18KK0083.

Publisher Copyright:
© 2021 Elsevier Ltd

Keywords

Ablation process modeling
Millimeter wave
Picosecond laser ablation
Subwavelength structure
Surface modification

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title = "Picosecond laser ablation of millimeter-wave subwavelength structures on alumina and sapphire",

abstract = "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 mm3/min and 20 mm3/min for structure heights of 900 μm and 750 μm 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 δ, which is assumed to depend on peak fluence, and on the threshold fluence ϕth. Using a best-fit procedure we find an average δ=630 nm and 650 nm, and ϕth=2.0-0.5+0.5 J/cm2 and 2.3-0.1+0.1 J/cm2 for alumina and sapphire, respectively, for peak fluence values between 30 and 70 J/cm2. With the best fit values, the model and data values for cumulative fluence agree to within 10%. Given inputs for δ and ϕth the model is used to predict average ablation rates as a function of SWS height and average laser power.",

keywords = "Ablation process modeling, Millimeter wave, Picosecond laser ablation, Subwavelength structure, Surface modification",

author = "Qi Wen and Elena Fadeeva and Shaul Hanany and J{\"u}rgen Koch and Tomotake Matsumura and Ryota Takaku and Karl Young",

note = "Funding Information: We acknowledge support provided by Trumpf GmbH & Co. KG (Ditzingen, Germany); the laser machining trials reported here were done at their laser application center. We thank Christopher Geach for helpful discussions. TM was supported by World Premier International Research Center Initiative (WPI), MEXT, Japan. This work was supported by JSPS KAKENHI Grant Number 18KK0083. Funding Information: We acknowledge support provided by Trumpf GmbH & Co. KG (Ditzingen, Germany); the laser machining trials reported here were done at their laser application center. We thank Christopher Geach for helpful discussions. TM was supported by World Premier International Research Center Initiative (WPI), MEXT, Japan. This work was supported by JSPS KAKENHI Grant Number 18KK0083. Publisher Copyright: {\textcopyright} 2021 Elsevier Ltd",

year = "2021",

month = oct,

doi = "10.1016/j.optlastec.2021.107207",

language = "English (US)",

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T1 - Picosecond laser ablation of millimeter-wave subwavelength structures on alumina and sapphire

AU - Wen, Qi

AU - Fadeeva, Elena

AU - Hanany, Shaul

AU - Koch, Jürgen

AU - Matsumura, Tomotake

AU - Takaku, Ryota

AU - Young, Karl

N1 - Funding Information: We acknowledge support provided by Trumpf GmbH & Co. KG (Ditzingen, Germany); the laser machining trials reported here were done at their laser application center. We thank Christopher Geach for helpful discussions. TM was supported by World Premier International Research Center Initiative (WPI), MEXT, Japan. This work was supported by JSPS KAKENHI Grant Number 18KK0083. Funding Information: We acknowledge support provided by Trumpf GmbH & Co. KG (Ditzingen, Germany); the laser machining trials reported here were done at their laser application center. We thank Christopher Geach for helpful discussions. TM was supported by World Premier International Research Center Initiative (WPI), MEXT, Japan. This work was supported by JSPS KAKENHI Grant Number 18KK0083. Publisher Copyright: © 2021 Elsevier Ltd

PY - 2021/10

Y1 - 2021/10

N2 - 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 mm3/min and 20 mm3/min for structure heights of 900 μm and 750 μm 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 δ, which is assumed to depend on peak fluence, and on the threshold fluence ϕth. Using a best-fit procedure we find an average δ=630 nm and 650 nm, and ϕth=2.0-0.5+0.5 J/cm2 and 2.3-0.1+0.1 J/cm2 for alumina and sapphire, respectively, for peak fluence values between 30 and 70 J/cm2. With the best fit values, the model and data values for cumulative fluence agree to within 10%. Given inputs for δ and ϕth the model is used to predict average ablation rates as a function of SWS height and average laser power.

AB - 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 mm3/min and 20 mm3/min for structure heights of 900 μm and 750 μm 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 δ, which is assumed to depend on peak fluence, and on the threshold fluence ϕth. Using a best-fit procedure we find an average δ=630 nm and 650 nm, and ϕth=2.0-0.5+0.5 J/cm2 and 2.3-0.1+0.1 J/cm2 for alumina and sapphire, respectively, for peak fluence values between 30 and 70 J/cm2. With the best fit values, the model and data values for cumulative fluence agree to within 10%. Given inputs for δ and ϕth the model is used to predict average ablation rates as a function of SWS height and average laser power.

KW - Ablation process modeling

KW - Millimeter wave

KW - Picosecond laser ablation

KW - Subwavelength structure

KW - Surface modification

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ER -

Picosecond laser ablation of millimeter-wave subwavelength structures on alumina and sapphire

Abstract

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Keywords

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