DYNAMIC COHERENCE MEASUREMENTS OF INDEX-GUIDED AND GAIN-GUIDED VCSEL

Coherence properties of several different types of VCSEL's are examine d with constant and modulated injection current with a bandwidth typic al of that used in telecommunications, Large signal modulation of inde x-guided single transverse-mode VCSEL's is found to reduce the coheren ce length by more than a factor of ten relative to the direct current configuration, Multiple transverse-mode index-guided VCSEL's have simi lar coherence lengths when operated de and modulated, and shorter than that of the single transverse-mode VCSEL's, Gain-guided multiple tran sverse-mode VCSEL's also have shorter coherence lengths than single tr ansverse-mode VCSEL's and under modulation can have coherence lengths as low as 0.5 cm.