A theoretical and experimental study of non-linear absorption properties of substituted 2,5-di-(phenylethynyl)thiophenes and structurally related compounds

Abstract

Photo-physical properties relevant for optical power limiting in the near-visible and visible regions of the spectrum are reported for a series of substituted diarylalkynyl chalcogenophenes (furans, thiophenes, selenophenes, and tellurophenes). The linear ground and excited state absorption as well as the nonlinear (two-photon) absorption were determined at the time-dependent density functional theory level with use of the hybrid exchange-correlation functionals B3LYP and CAM-B3LYP. A selected number of the theoretically studied molecules were synthesized and characterized experimentally with the use of absorption and luminescence spectroscopy. The photo-physical data are compared to the results from optical power limiting measurements performed in THF solution at a wavelength of 532 nm, with a laser pulse length of 5 ns and pulse energies up to 150 µJ. The best compounds in the present investigation display an energy damping by approximately a factor of 10 at a concentration of 0.010 M.

Keywords:

• density functional theory
• two-photon absorption
• excited state absorption
• optical limiting
• chalcogenophenes
• thiophenes
• DFT
• TPA

Acknowledgements

This work was supported (BE, CL, ML, PN) by a Swedish Defence Nanotechnology Programme run jointly by the Swedish Defence Research Agency (FOI) and Defence Material Administration (FMV). ML acknowledges a grant from The Research Council of Norway within the NanoMat program, contract #163529.