Li, Qianliang, Perrie, Walter, Tang, Yue 
ORCID: 0000-0002-4232-2513, Allegre, Olivier, Ho, Janet, Chalker, Paul ORCID: 0000-0002-2295-6332, Li, Zhaoqing, Edwardson, Stuart P ORCID: 0000-0001-5239-4409 and Dearden, Geoff ORCID: 0000-0003-0648-7473
(2020)
Ablation of amorphous Polyethy( ethyl)letone (PEEK) by a femtosecond Ti:sapphire laser.
In: Laser-based Micro- and Nanoprocessing XIV, 2020-2-1 - 2020-2-6.
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Abstract
Laser micro-machining of amorphous PEEK has been demonstrated with 180 fs/1 kHz NIR (775 nm) and NUV (387 nm) laser pulses. The single pulse ablation threshold was found to be 2.01 ± 0.05 J/cm2 and 0.23 ± 0.02 J/cm2 at 775 nm and 387 nm respectively. The significant difference in ablation threshold is due to the requirement for 3-photon absorption at 775 nm, where PEEK is transparent while significant linear absorption within the material bandgap occurs at 387 nm, enhancing 2-photon absorption. A high 2-photon absorption coefficient, measured to be β387 ∼ 38 cm GW-1 supports this view while at the bandgap edge, 400 nm, β400 ∼ 0.7 cm GW-1. Multi-pulse exposure yields incubation coefficients of S775 = 0.72 ± 0.01 and S387 = 0.85 ± 0.02 hence incubation is significantly reduced in the NUV. Ablation of PEEK with NUV fs pulses demonstrates much reduced melting and re-deposition, thus precision NUV polymer micromachining is accomplished while laser induced periodic surface structures (LIPSS) with pitch Λ < 0.4 μm are observed at the base of ablated regions. Scanned areas exhibit white light diffraction due to this sub-micron periodic surface modulation. With the aid of a phase only spatial light modulator, multi-beam NUV micro-structuring is achieved, speeding micro-processing while reaching a line width < 4 μm with NA = 0.4 objective.
| Item Type: | Conference or Workshop Item (Unspecified) |
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| Uncontrolled Keywords: | PEEK, Femtosecond pulsed laser, Micro-machining, Ablation threshold, Incubation effect, Nonlinear absorption |
| Depositing User: | Symplectic Admin |
| Date Deposited: | 11 Aug 2020 07:38 |
| Last Modified: | 18 Jan 2023 23:37 |
| DOI: | 10.1117/12.2543735 |
| Related URLs: | |
| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3097045 |
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