Whispering Gallery Mode Laser from Carbon Dot-NaCl Hybrid Crystals.

Carbon dot (CD)-NaCl hybrid crystals are obtained by incorporating the CDs into NaCl matrix through a simple process. The embedded CDs have added the luminescence centers into NaCl, and as a result, the hybrid crystals present the fluorescence centered at 510 nm under the illumination of 365 nm light. Meanwhile, the phosphorescence with an average lifetime of 314 ms is achieved after the 365 nm light was turned off. Furthermore, optical gain and lasing phenomenon has been observed from hybrid crystals. When the pump power is low, a weak spontaneous emission can be observed from the hybrid crystal, whereas the lasing action was observed under high pump power. The lasing threshold is found to be 0.08 mW and corresponding Q factor is calculated to be 447. The tiny cubic crystal in hybrid crystals offers the whispering gallery mode (WGM) resonant cavity for lasing emission. That has provided a new approach for realizing lasing materials.