Design And Thermal Analysis Of A 10kW Rectangular Spot Space Incoherent Beam Combiner Space Incoherent Beam Combiner

With the practical application of industrial high-power lasers and their auxiliary equipment,advanced laser technology is closely combined with the upgrading of the surface strengthening and modification technology of various large-scale equipment parts.The laser metal material surface heat treatment technology is used as the surface strengthening and modification technology of metal materials.It is one of the most effective means of modification and has been a research hot spot at home and abroad.The laser beam with a rectangular cross-section of fiber transmission can not only effectively improve the efficiency of laser heat treatment,but also can implement flexible laser heat treatment inside small parts.When the optical lens in the high-power laser system absorbs high-energy-density laser energy and produces a large temperature gradient inside it,the optical lens will be thermally deformed and the transmittance will change accordingly,thereby affecting the laser of the high-power laser system Transmission quality,so the optical-mechanical-thermal integrated analysis of the beam combiner is particularly important.In this paper,18 optical fiber output 972 nm semiconductor laser beams are arranged in parallel in a matrix.Through beam collimation and spatially incoherent beam combination,a 10 kW class combined laser beam with rectangular spot characteristics is obtained.Theoretical analysis of the radius of the collimated laser beam,the distance between adjacent beams and the spot overlap rate of the combined laser,the use of optical design software to establish the structure model of the beam combiner and the optical simulation software to simulate the energy distribution of the combined laser spot on this basis,the development of a 10 kW 18×1 rectangular spot laser beam combiner was completed.Within a combined beam length of 200 mm,a combined laser output with a single rectangular spot shape,a maximum combined beam power of 10.249 kW,a focal spot size of 31 mm×11 mm,a center wavelength of 972.34 nm,and a spectral line width of 2.27nm was achieved.Use finite element analysis software to establish a finite element thermal analysis model for the optical lens of the rectangular spot laser beam combiner,and use a thermal imager to measure the temperature of the window mirror when the 10 kW laser beam is combined to obtain air convective heat exchange that meets the actual situation.The coefficient measured value is corrected to the finite element thermal analysis model,so as to obtain the temperature field,deformation and thermal stress simulation value of all optical lenses in the rectangular spot laser beam combiner when the 10 kW combined laser beam is irradiated for 200 s.The maximum temperature difference simulation value of the optical lens is 89.131?,the maximum deformation simulation value is 1.21×10^-6 m,and the corresponding maximum thermal stress simulation value of 4.74×10⁶ Pa is less than the thermal damage threshold value of 60×10⁶ Pa for ultraviolet fused silica optical glass.All optical lenses will not be damaged by thermal stress.On this basis,using Zernike polynomials as the interface tool between the finite element analysis software and the optical design software,the mirror surface obtained by the finite element analysis is brought into the optical design software,and all the optical lenses in the rectangular spot laser beam combiner are obtained.The amount of change in the radius of curvature of the smooth surface.When the 10 kW combined laser is irradiated for 200 s,the maximum change in the radius of curvature of the optical lens clear surface is 0.1aperture,which is smaller than the optical lens processing tolerance of±1 aperture,thus further verifying the working reliability and structural stability of the beam combiner.