Acoustical monitoring of laser-matter interaction using nanosecond radiation pulses with periodically modulated intensity

• Published in: Journal of physics. Conference series Vol. 1439; no. 1; pp. 12019 - 12024
• Main Authors: Zubko, A E, Samokhin, A A, Shashkov, E V, Vorob'ev, N S
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.01.2020
• Subjects: Displacement; Fluence; Irradiation; Laser ablation; Lasers; Light emission; Lithium niobates; Photodiodes; Physics; Pressure pulses; Radiation; Vaporization
• ISSN: 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/1439/1/012019

Nanosecond laser ablation of metal target under the action of radiation pulses with periodically modulated intensity is investigated. Generated pressure pulses are detected by piezo-transducer (lithium niobate) on the back target side. Such approach permits to measure simultaneously recoil pressure behavior and calculate the irradiated surface displacement during laser action by comparison modulated parts of laser and acoustic signals. Nanosecond laser pulses contain 10-15 short peaks of 60 ps duration (1.08 μm wavelength) which provide fluence values up to 30 J cm−2 in the pulse. Plasma light emission is also registered with the help of photodiode. At the considered fluences surface displacement during the pulse turns out to be considerably smaller than theoretical estimation for free vacuum vaporization and measured experimental displacement which follows from the arrival time delay of another pressure signals generated with subsequent laser pulse directed to the same spot. Such behavior can be evidence that crater formation in the considered irradiation regime occurs after the pulse end.