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Systematic investigation of single- and multi-mode operation in vertical-external-cavity surface-emitting lasers

We systematically study the single- and multi-mode emission of vertical-external-cavity surface-emitting lasers (VECSELs) using streak camera measurements and interferometric measurement techniques. In all experiments, the VECSEL chip is based on (GaIn)As multi-quantum wells as active medium designed for laser emission around 1010 nm. The emission is analyzed in dependence of the pump power, employing two resonator designs as well as different output couplers. We monitor the evolution of emission bandwidth and show that in our setups a stable two-color lasing –with both lasing intensities sharing the same gain region on the chip– is related to a sufficiently high number of longitudinal modes participating in the laser emission.