With certain emitter beam quality and BPP allowed by fiber, we have derived a spatial beam combination structure that approaches the BPP limit of the fiber. Using the spatial beam combination structure and polarization beam combination, BWT has achieved 1.1KW output from a fiber (one end coated) with NA 0.22 and core diameter of 200μm. The electro- optical efficiency is nearly 47%. Multiple emitters with wavelength of 976nm are packaged in a module with size of 600 ×350×80mm<sup>3</sup>.
With continuous increase in output power of fiber lasers, small volume, low weight, high electro-optic efficiency and high brightness diode laser pump source has become the trend of development. Using spatial beam combining and polarization beam combining methods, BWT has developed a compact pump laser achieving 600W level out of a fiber of 0.22 NA and 200 μm core diameter. At 12A, electro-optical efficiency is higher than 49%. Its brightness is higher than that of the commercially available 158W pump from BWT.
Proc. SPIE. 9733, High-Power Diode Laser Technology and Applications XIV
KEYWORDS: Energy efficiency, Diffraction, Mirrors, Polarization, High power lasers, Reflectivity, Semiconductor lasers, Collimation, High power fiber lasers, Beam shaping, Electro optics, Diffraction gratings
Spectral beam combination expands the output power while keeps the beam quality of the combined beam almost the same as that of a single emitter. Spectral beam combination has been successfully achieved for high power fiber lasers, diode laser arrays and diode laser stacks. We have recently achieved the spectral beam combination of multiple single emitter diode lasers. Spatial beam combination and beam transformation are employed before beams from 25 single emitter diode lasers can be spectrally combined. An average output power about 220W, a spectral bandwidth less than 9 nm (95% energy), a beam quality similar to that of a single emitter and electro-optical conversion efficiency over 46% are achieved.<p> </p> In this paper, Rigorous Coupled Wave analysis is used to numerically evaluate the influence of emitter width, emitter pitch and focal length of transform lens on diffraction efficiency of the grating and spectral bandwidth. <p> </p>To assess the chance of catastrophic optical mirror damage (COMD), the optical power in the internal cavity of a free running emitter and the optical power in the grating external cavity of a wavelength locked emitter are theoretically analyzed. <p> </p>Advantages and disadvantages of spectral beam combination are concluded.