Temperature and intensity dependence of Yb-fiber laser light absorption in water

Abstract

Absorption of CW Yb-fiber laser light of 1.07 μm wavelength in water has been measured at different water temperatures and laser intensities. The absorption coefficient was estimated to be 0.135 cm(-1) at 25 °C water temperature, and this was found to decrease with temperature at a rate of 5.7 × 10(-4) cm(-1) °C(-1). The absorption coefficient increased significantly when the laser beam was focused in water, and the increase depended on the distance of the focal point from the water surface. This has been attributed to the absorption and scattering losses of laser radiation in a cavity formed in water by the focused beam at laser intensities in the megawatts per square centimeter and higher range.

An investigation on co-axial water-jet assisted fiber laser cutting of metal sheets

“…It has been reported that 1.07 μm wavelength radiation has a low absorption in water [21]. Therefore, all the three types of cutting experiments were conducted using a Yb-fiber laser operating at 1.07 μm wavelength.…”

An investigation of energy loss mechanisms in water-jet assisted underwater laser cutting process using an analytical model

“…For 1.07 μm laser wavelength the absorption coefficient of water and the reflectivity at water surface are $0.135 cm À 1 and $2.0%, respectively [22]. At high laser intensities the absorption coefficient of water does not remain linear; instead it becomes a function of incident laser power (P L ), laser beam diameter at the water surface (2w s ) and at the focal point (2w 0 ), location of the focal point with respect to water surface (L 1 ) and the total water column height (L) [22]. The total water column height, L includes distance of the focal point from water surface (L 1 ) and water column height beyond focal point (L 2 ).…”

“…Laser absorption in water can be estimated using Eq. (23) [22]. where, α L is the linear absorption coefficient of water at 1.07 μm wavelength.…”

“…the velocity of melt isotherm, v m can be derived in terms of water-jet speed, melt layer velocity and other material properties, and can be expressed by Eq (22). …”

Experimental investigation of underwater laser beam micromachining (UW-LBμM) on 304 stainless steel

“…The mechanisms of UW-LBμM for various lasers are different due to change in absorption coefficient of water at different wavelengths. The absorption coefficient of water for 10.6-μm wavelength CO 2 laser, 1.06 μm, and 532-nm wavelength Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG) laser are 500, 0.148, and 0.0005 cm −1 , respectively [23][24][25]. Due to high absorption of water for 10.6-μm wavelength CO 2 laser, a larger portion of laser energy vaporizes the water and forms a conical keyhole along the water thickness to allow laser beam to reach workpiece material surface [23].…”