Superior single-mode lasing in a self-assembly CsPbX3 microcavity over an ultrawide pumping wavelength range

All-inorganic perovskite micro/nanolasers are emerging as a class of miniaturized coherent photonic sources for many potential applications,such as optical communication,computing,and imaging,owing to their ultracompact sizes,highly localized coherent output,and broadband wavelength tunability.However,to achieve singlemode laser emission in the microscale perovskite cavity is still challenging.Herein,we report unprecedented single-mode laser operations at room temperature in self-assembly Cs Pb X3 microcavities over an ultrawide pumping wavelength range of 400–2300 nm,covering one-to five-photon absorption processes.The superior frequency down-and upconversion single-mode lasing manifests high multiphoton absorption efficiency and excellent optical gain from the electron–hole plasma state in the perovskite microcavities.Through direct compositional modulation,the wavelength of a single-mode Cs Pb X3 microlaser can be continuously tuned from blue-violet to green(427–543 nm).The laser emission remains stable and robust after long-term high-intensity excitation for over 12 h(up to 4.3×107 excitation cycles)in the ambient atmosphere.Moreover,the pump-wavelength dependence of the threshold,as well as the detailed lasing dynamics such as the gain-switching and electron–hole plasma mechanisms,are systematically investigated to shed insight into the more fundamental issues of the lasing processes in Cs Pb X3 perovskite microcavities.

High-precision group-delay dispersion measurements of optical fibers via fingerprint-spectral wavelength-to-time mapping

The group-delay dispersion of an optical fiber was measured with the time-of-flight method, using fingerprint-like characteristic spectra from a mode-locked fiber laser source. To determine the group-delay dispersion up to the fourth order, least-squares fitting was applied to the overall time waveform mapped on the time axis for the fingerprint-spectral broadband pulses through a long optical fiber. The analysis of all 4003 data points reduced statistical uncertainty, and provided second-, third-, and fourth-order dispersion with uncertainties of 0.02%, 0.4%, and 4%,respectively.