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

Ultrastable and Low‐Threshold Random Lasing from Narrow‐Bandwidth‐Emission Triangular Carbon Quantum Dots

“…The plots of the blue, green, and red integrated random lasing emission intensity and FWHM of the narrow spikes in the random lasing emission spectra as a function of the pump energy density are displayed in Figure d–f. Significantly, as a direct benefit of the very small Stokes shifts and small FWHM of NBE‐T‐CQDs, which can facilitate the ultrafast build‐up of population inversion and the subsequent optical amplification at a low pump energy density, the pump thresholds are determined to be as low as 0.087, 0.052 and 0.048 mJ cm −2 for blue, green, and red random lasers, respectively, which is two orders of magnitude lower than that of our previous reported CQDs‐based random lasers (2.1–5.8 mJ cm −2 ), and even superior to that of the perovskites and traditional colloidal semiconductor QDs‐based lasers (0.05–2 mJ cm −2 ) . It can be clearly observed that as the power energy density increases, the FWHM of the blue, green, and red random lasing emission spectra all decrease significantly from 30 nm to the subnanometer scale when the pump energy density is higher than their thresholds, which is the typical characteristic of the random lasing (Figure d–f and Figure S4, Supporting Information) .…”

“…Indeed, they display strong and narrow excitonic absorption peaks centered at 460 (B‐), 498 (G‐), and 582 nm (R‐NBE‐T‐CQDs), and sharp excitonic emission peaks centered at 472 (B‐), 507 (G‐), and 598 nm (R‐NBE‐T‐CQDs) with extremely narrow FWHM values of only 30, 29, and 30 nm, respectively. Moreover, the NBE‐T‐CQDs also exhibit very small Stokes shifts of 12, 9, and 16 nm for the B‐, G‐, and R‐NBE‐T‐CQDs, respectively (Figure d–f), much smaller than those of the previously reported CQDs (Stokes shifts > 80 nm) . The rather small Stokes shifts (9–16 nm) and small FWHM (30 nm) of the NBE‐T‐CQDs are even superior to that of the well‐developed perovskites and Cd 2+ ‐based QDs (Stokes shifts < 20 nm, FWHM < 40 nm) .…”

“…The bandgap emission carbon quantum dots (BE‐CQDs) have recently emerged as a promising alternative to perovskites and traditional semiconductor QDs for optoelectronic devices, such as solution‐processed electroluminescent light‐emitting diodes (LEDs) and lasers, by taking advantage of carbon's intrinsic merits of high stability, low cost, high abundance, and environment friendliness . In our recent work, for the first time, we have realized full‐color random lasing with lasing thresholds in the range of 2.1–5.8 mJ cm −2 in blue, green, red, and white colors based on bright multicolor fluorescent BE‐CQDs .…”

“…The random lasers show much better operating stability than those of perovskites and Cd 2+ ‐based QDs, laying a solid foundation for developing the next‐generation laser technology . However, the large Stokes shifts (>80 nm) and the large full width at half maximum (FWHM > 80 nm) of the BE‐CQDs inevitably result in the dissipation of exciton energy into heat and prevent sustaining population inversion during the pumping process, thus fundamentally limiting the further performance improvement especially on pump thresholds for the random lasing . Without a doubt, the best approach to realizing tunable stable CQDs‐based random lasers with a much lower pump threshold for lasing is to develop bright multicolor fluorescent CQDs with small Stokes shifts (<20 nm) and small FWHM (<40 nm).…”

Fabrication of amido group functionalized carbon quantum dots and its transparent luminescent epoxy matrix composites

“…Such nanocomposite exhibited the prominent UV‐absorbing capability and the high optical transparency in the visible‐wavelength region. Yu functionalized CQDs surface with organosilane groups, and high photoluminescence emission efficiency was achieved under 450 nm wavelength excitation. The quantum yield of surface functionalized CQDs dispersed in epoxy can be enhanced to 68%.…”