Low-Threshold High-Quality Room-Temperature Multi-Photon-Pumped Blue Lasing from a Novel D-π-A Ladder-Type Oligo(p-phenylene)

Optically pumped upconversion lasing is highly useful and viable for practical applications in high-density integrated optoelectronic devices. However, realization of multiphoton pumped blue lasing under high-repetition-rate pumping at room temperature still poses a great challenge. Herein, we have demonstrated that multiphoton pumped blue lasing using high-frequency pumping sources carried out at room temperature has been achieved in the whispering-gallery-mode microspheres doped with a novel laser gain medium based on D-π-A ladder-type oligo(p-phenylene). Remarkably, a low threshold (81.90 µJ cm⁻²) and high Q factor (1370) blue lasing has been obtained under two-photon-pumped excitation by a high repetition rate of 76 MHz 800 nm femtosecond laser at room temperature. Furthermore, three-photon-pumped room-temperature blue lasing has been achieved with an ultralow threshold of 4.73 mJ cm⁻². Comprehensive spectral analysis explicitly demonstrated characteristic WGM lasing features under both two-photon- and three-photon-pumped excitations. These findings are in excellent agreement with numerical simulations and theoretical calculations, substantiating the experimental results quantitatively. Our work introduces a new avenue to develop high-performance multiphoton optically pumped coherent light sources in the blue spectral region, which will greatly stimulate further research interests in nonlinear optics, all-optical circuits, and its fundamental sciences and potential applications in optoelectronics.