Spatially mapping random lasing cavities

A mapping technique is developed to spatially resolve random laser emission spectra from disorder solid media with optical gain above the threshold excitation intensity for lasing; the technique is applied to rr-conjugated polymer lms. By mapping the spatial extent of emission peaks in the random laser spectrum, bright areas that correspond to naturally-formed lasing microcavities are unraveled. The size of the obtained microcavities matches the size extracted from the Fourier transform analysis of the laser emission spectrum. Mapping at increased excitation intensities show multiple resonant microcavities that lase at increasing threshold intensities.