title: Highly Efficient Multiphoton-Pumped Frequency-Upconversion Stimulated Blue Emission with Ultralow Threshold from Highly Extended Ladder-Type Oligo(p-phenylene)s.
abstract: A series of highly extended π-conjugated ladder-type oligo(p-phenylene)s containing up to 10 phenyl rings with (L)-Ph(n)-NPh (n=7-10) or without diphenylamino endcaps (L)-Ph(n) (n=7 and 8) were synthesized and investigated for their multiphoton absorption properties for frequency upconverted blue ASE/lasing. Extremely large two-photon absorption (2PA) cross-sections and highly efficient 2PA ASE/lasing with ultralow threshold were achieved. (L)-Ph(10)-NPh exhibits the highest intrinsic 2PA cross-section of 3643 GM for a blue emissive organic fluorophore reported so far. The record-high 2PA pumped ASE/lasing efficiency of 2.06 % was obtained by un-endcapped oligomer, (L)-Ph(8) rather than that with larger σ2 , suggesting that a molecule with larger σ2 is not guaranteed to exhibit higher η2 . All of these oligomers exhibit exceptionally ultralow 2PA pumped ASE/lasing thresholds, among which the lowest 2PA pumped threshold of circa 0.26 μJ was achieved by (L)-Ph(10)-NPh.
authors.affiliation: Department of Chemistry, Institute of Advanced Materials and Institute of Molecular Functional Materials, Hong Kong Baptist University, Hong Kong SAR, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Guo
authors.affiliation: Department of Physics and Institute of Advanced Materials, Hong Kong Baptist University, Hong Kong SAR, China.
authors.forename: King Fai
authors.initials: KF
authors.lastname: Li
authors.affiliation: College of Preclinical Medicine, Southwest Medical University, Luzhou, 646000, China.
authors.forename: Xiaoqin
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Physics and Institute of Advanced Materials, Hong Kong Baptist University, Hong Kong SAR, China. kwcheah@hkbu.edu.hk.
authors.forename: Kok Wai
authors.initials: KW
authors.lastname: Cheah
authors.affiliation: Department of Chemistry, Institute of Advanced Materials and Institute of Molecular Functional Materials, Hong Kong Baptist University, Hong Kong SAR, China. mswong@hkbu.edu.hk.
authors.forename: Man Shing
authors.initials: MS
authors.lastname: Wong
keywords: amplified spontaneous emission; blue lasing; ladder oligomers; multiphoton absorption; oligophenylenes