Near-field measurement of quantum dot broad area laser diodes by utilizing near-field scanning optical microscope: Effects of the linewidth enhancement factor on filamentation

Near-field scanning optical microscopy (NSOM) studies of broad area laser diodes (BALD) with different structures of quantum dot (QD) and quantum well (QW) were performed. The values of α-factor for the two types of BALD were measured as 0.6 (QD) and 2 (QW), respectively. Near-field measurements show that the filamentation in the BALD is closely related to the α-factor. Moreover, the high resolution (<100 nm) of NSOM provides a detailed mapping of the BALDs output from the active region.