Whispering Gallery Mode Selection in Quantum Dot Microdisk Lasers Under Spatially Inhomogeneous Optical Pumping

Spectral characteristics of quantum dot (QD) microdisk lasers under spatially inhomogeneous optical excitation are investigated. By varying the position and size of the continuous-wave excitation spot over the laser cavity, we demonstrate controllable selection and switching of lasing whispering gallery modes (WGMs) at room temperature. Experimental results show that shifting the excitation spot across the surface of 10 μm microdisk laser enables reversible wavelength switching between WGMs at 1285 nm and 1313 nm, corresponding to different radial mode orders. Theoretical modeling and near-field scanning optical microscopy confirm that the observed spectral switching of lasing WGM is caused by spatially selective charge carrier distribution arising from the suppressed lateral transport of charge carriers in quantum dot active region. The findings highlight the potential for actively spectral switchable microlasers for applications in photonic integration and optical sensing.