Wide-bandwidth lasing from C-dot/epoxy nanocomposite Fabry–Perot cavities with ultralow threshold

We show that by maximizing the amount of organosilane functional groups, the quantum yield of surface functionalized carbon nanodots (C-dots) dispersed in epoxy can be enhanced to 68% under optical excitation at 450 nm wavelength. This is the highest quantum yield ever recorded for C-dots at such an excitation wavelength. Lasing emission can also be demonstrated from a Fabry–Perot cavity by using C-dots as the gain medium. The lasing threshold is found to be ∼200 W cm−2 which is 2 orders of magnitude lower than that provided in the recent reports. Furthermore, tunable single-mode lasing over a bandwidth of ∼60 nm wide is achieved from the Fabry–Perot cavity in the Littrow configuration.