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.