title: Ultralow-threshold multiphoton-pumped lasing from colloidal nanoplatelets in solution.
abstract: Although multiphoton-pumped lasing from a solution of chromophores is important in the emerging fields of nonlinear optofluidics and bio-photonics, conventionally used organic dyes are often rendered unsuitable because of relatively small multiphoton absorption cross-sections and low photostability. Here, we demonstrate highly photostable, ultralow-threshold multiphoton-pumped biexcitonic lasing from a solution of colloidal CdSe/CdS nanoplatelets within a cuvette-based Fabry-Pérot optical resonator. We find that colloidal nanoplatelets surprisingly exhibit an optimal lateral size that minimizes lasing threshold. These nanoplatelets possess very large gain cross-sections of 7.3 × 10(-14) cm(2) and ultralow lasing thresholds of 1.2 and 4.3 mJ cm(-2) under two-photon (λexc=800 nm) and three-photon (λexc=1.3 μm) excitation, respectively. The highly polarized emission from the nanoplatelet laser shows no significant photodegradation over 10(7) laser shots. These findings constitute a more comprehensive understanding of the utility of colloidal semiconductor nanoparticles as the gain medium in high-performance frequency-upconversion liquid lasers.
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Mingjie
authors.initials: M
authors.lastname: Li
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Min
authors.initials: M
authors.lastname: Zhi
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Hai
authors.initials: H
authors.lastname: Zhu
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Wen-Ya
authors.initials: WY
authors.lastname: Wu
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Qing-Hua
authors.identifier: http://orcid.org/0000-0002-4153-0767
authors.initials: QH
authors.lastname: Xu
authors.affiliation: Institute of High Performance Computing A*STAR, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632, Singapore.
authors.forename: Mark Hyunpong
authors.initials: MH
authors.lastname: Jhon
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.|Institute of Materials Research &Engineering A*STAR, 3 Research Link, Singapore 117602, Singapore.|Microfluidics Systems Biology Lab, Institute of Molecular and Cell Biology A*STAR, 61 Biopolis Drive, Singapore 138673, Singapore.
authors.forename: Yinthai
authors.initials: Y
authors.lastname: Chan