Vertical-cavity surface emitting laser-diodes arrays expanding the range of high-power laser systems and applications

Abstract

Thermal treatment may be by far the most frequent process used in manufacturing, but only at a few places lasers could make an inroad. For thermal treatment, homogeneous illumination of large areas at a lower brightness, and accurate temporal as well as spatial control of the power is required. This is complicated for conventional high-power lasers, while vertical-cavity surface emitting laser-diode (VCSEL) arrays inherently have these capabilities. Because of their fast switching capability and low power dissipation, VCSELs have been widely used for datacom and sensing applications. By forming large-area arrays with hundreds of VCSELs per mm2, their use can be further expanded to high-power applications. In this way, power densities of several W/mm2 are achieved, making the VCEL arrays an ideal solution for many heating applications, ranging from melting and welding of plastics and laminates to curing, drying, and sintering of coatings. A turn-key system concept has been developed allowing fast and easy configuring systems to the specifications of the applications. The compact and robust system can be built directly into the manufacturing equipment, thus making expensive fibers and homogenizing optics superfluous. These systems are now finding their first inroads into industrial applications and have been designed-in into commercially available production machines.

Optimization of the Laser Hardening Process by Adapting the Intensity Distribution to Generate a Top-hat Temperature Distribution Using Freeform Optics

“…Coatings 2017, 7,77 The first laser profile in Figure 1a represents the measured beam of a defocused Laserline 4.5 kW diode laser source with 33 mm mrad. In the focal plane, the laser beam had a 1 mm spot diameter and in the defocused plane about 40 mm.…”

“…Coatings 2017, 7,77 stationary status. The dependency of the specific values of the temperature cannot be taken into account.…”

“…Coatings 2017, 7,77 movement of the axis of a robot or another handling system. If the speed of the spot on the surface is way higher than the heat conduction, it can be assumed that the intensity distribution generated on the work piece is equal to the integration of the movement in one time period [9,10].…”

“…To achieve the necessary power density most HPDL need a superposition of several laser beams provided by so called diode stacks. Current research points that in the future direct emitting laser diodes will reach high enough power densities to actually emit light directly onto the surface [7]. Besides other benefits the intensity distribution of these sources can be easily adjusted by switching individual diode arrays of the stacks on and off.…”

Optically pumped VECSELs: review of technology and progress

“…Higher output power can be obtained by increasing the aperture area, but again at the expense of degraded beam quality. In multimode operation, large arrays of multi-emitter VCSELs can produce several kW of output power [12,13] and are used in infrared illumination and industrial applications, for example.…”