Ultralow-threshold up-converted lasing in oligofluorenes with tailored strong nonlinear absorption

Burak Guzelturk, Alexander L. Kanibolotsky, Clara Orofino-Pena, Nicolas Laurand, Martin D. Dawson, Peter Skabara, Hilmi Volkan Demir

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)
49 Downloads (Pure)


Nonlinear optical response in organic semiconductors has been an attractive property for many practical applications. For frequency up-converter lasers, to date, conjugated polymers, fluorescent dyes and small organic molecules have been proposed but their performances have been severely limited due to the difficulty of simultaneously achieving strong nonlinear optical response and high performance optical gain. In this work, we show that structurally designed truxene-based star-shaped oligofluorenes exhibit strong structure-property relationships enabling enhanced nonlinear optical response with favorable optical gain performance. As the number of fluorene repeat units in each arm is increased from 3 to 6, these molecules demonstrate a two-photon absorption cross-section as high as 2200 GM, which is comparable to that of linear conjugated polymers. Tailored truxene oligomers with six fluorene units in each arm (T6) show two-photon absorption pumped amplified spontaneous emission with a threshold as low as 2.43 mJ/cm2, which is better than that of the lowest reported threshold in organic semiconductors. Furthermore, we show a frequency up-converted laser using the newly designed and synthesized star-shaped oligomer T6 with a threshold as low as 3.1 mJ/cm2, which is more than an order of magnitude lower than that of any conjugated polymer. Thus, these oligomers with enhanced nonlinear optical properties are highly attractive for bio-integrated applications such as photodynamic therapy and in-vivo bio-sensing.
Original languageEnglish
Pages (from-to)12018-12025
Number of pages8
JournalJournal of Materials Chemistry. C
Issue number46
Early online date13 Oct 2015
Publication statusE-pub ahead of print - 13 Oct 2015


  • organic semiconductors
  • conjugated polymers
  • fluorescent dyes
  • oligofluorenes


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