
Broad area laser in external resonator
What:
(Almost) fundamental mode operation of broad area diode lasers in external resonator.
Why:
 Higher power densities
 frequency conversion (SHG, upconversion)
 Coupling into single mode fibers
 pumping of microchip lasers
 welding of plastic components
 illumination, bleaching, heating et.al. with micrometer precision
How:
external resonators for influencing transversal modenstructure
Starting point:
Transversal multimodeoperation ca. 60fold worse than physical limit at 2W optical power.
Ansatz:
novel resonator concept:
 stable resonator along slowaxis
 optional modefiltering
 operation not along optical axis but under angle
Resonator



Results
Improvement in brightness by factor 12
Variabel between 0.4W optical power with M^{2} = 1.03 and 1.1W optical power with M^{2} = 2.7



The intensity distribution in the beam waist at an output power of 400mW is identical to a gaussian distribution
except for small deviations in the tails.

The beam caustic as measured behind an f=75 mm lens at an output power of 400mW yields an M^{2} = 1,03.



The intensity distribution in the beam waist at an output power of 1.1W shows small deviations from an ideal
gaussian distribution.

The beam caustic as measured behind an f=75 mm lens at an output power of 1.1W yields an M^{2} = 2,7.

Feasability study



first short Video (2.9 MB)

second short video (5.9 MB)



Danilo Skoczowsky

