Compact high brightness diode laser emitting 500W from a 100μm fiber

Abstract

High power, high brightness diode lasers are beginning to compete with solid state lasers, i.e. disk and fiber lasers. The core technologies for brightness scaling of diode lasers are optical stacking and dense spectral combining (DSC), as well as improvements of the diode material. Diode lasers have the lowest cost of ownership, highest efficiency and most compact design among all lasers.Multiple Single Emitter (MSE) modules allow highest power and highest brightness diode lasers based on standard broad area diodes. Multiple single emitters, each rated at 12 W, are stacked in the fast axis with a monolithic slow axis collimator (SAC) array. Volume Bragg Gratings (VBG) stabilizes the wavelength and narrow the linewidth to less than 1 nm. Dichroic mirrors are used for dense wavelength multiplexing of 4 channels within 12 nm. Subsequently polarization multiplexing generates 450 W with a beam quality of 4.5 mm*mrad.Fast control electronics and miniaturized switched power supplies enable pulse rise times of less than 10 µs, with pulse widths continuously adjustable from 20 µs to cw. Further power scaling up to multi-kilowatts can be achieved by multiplexing up to 16 channels. The power and brightness of these systems enables the use of direct diode lasers for cutting and welding. The technologies can be transferred to other wavelengths to include 793 nm and 1530 nm. Optimized spectral combining enables further improvements in spectral brightness and power.Keywords: High power diode laser, high brightness diode laser, fiber coupling, spectral combining, narrow bandwidth, wavelength stabilization, short pulses BACKGROUNDHigh power diode lasers find an increasing number of applications in materials processing and pumping of solid state lasers as their brightness increases. Beyond improvements in the design of the diodes themselves -for minimum slow axis divergence, highest power from a given size aperture and improved wall plug efficiency -optical and spectral stacking are deployed to scale power and brightness. Single emitters and minibars allow the highest brightness from the diode aperture. Single emitters typically deliver 12 W from a 100 µm aperture with 11 o slow axis divergence resulting in a similar brightness per emitter as minibars with up to 8 W from the aperture. Minibars require additional optics for beam shaping that can be omitted for single emitters. Single emitters also require low drive currents up to 15 A, which can be easily modulated with more than 100 kHz. Due to the low current cost effective power supplies are available. Furthermore, single emitter chip on submount (COS) is an established component that is available from various suppliers at a variety of different wavelengths and with exceptional ensemble reliabilities of tens of thousands of hours.Optical stacking is state of the art for power scaling, and many different configurations are available for bars and single emitters. Spectral stacking allows scaling of brightness and power. A narrow and stable spectrum of individual diodes is require...

Research on fiber coupling technology of kilowatt laser diode by single emitters

“…The output power of 8w fiber-coupled single-emitters diode laser is combined by using two modules, that is, eight 19x1 fiber combiners with the beam combining efficiency more than 96 %. And eight output fibers are shaped and focused, The output power reaches 1453w, the spot size is 2.25mm*1.1mm, and the power density reaches 6x10 4 w/ cm 2 . Meet the requirements of metal laser cladding.…”

“…For diode laser, because of its complex beam, it is difficult to accurately solve the mode-field distribution, so the geometric optical coupling theory is generally adopted. According to the theory of geometrical coupling, two conditions are needed to be satisfied when the beam is coupled into the fiber: the incident diameter of the beam must be smaller than the core diameter of the fiber; the beam must meet the total reflection condition during transmission [4][5][6]. In figure 1, the laser beam coupling condition can be expressed as equation (1) and (2): …”

Fiber-coupled high-power diode-lasers with highest radiance

“…Only deep welding results could be demonstrated. [3] In the last years new techniques based on wavelength stabilization with dense wavelength multiplexing have been demonstrated and results of more than 500W in 50µm fiber with NA 0.22 were shown, which is equivalent to a radiance in the range of 10 8 W/cm²sr [4,5]. These techniques allow radiances more than one order of magnitude higher.…”

Thin film filter wavelength-locked laser cavity for spectral beam combining of diode laser arrays

“…Those systems are suited to serve all kind of high-brightness continuous-wave kW-class metal processing applications [1][2][3][4][5]. Compared to dissipative optically-pumped solid-state lasers, direct diode lasers potentially exhibit enhanced electrical-to-optical conversion efficiency of up to 45 % allowing customers to lower their costs of ownership.…”