Abstract
This study demonstrates a measurement system for a non-degenerate two-photon absorption (NDTPA) spectrum. The NDTPA light sources are a white light super continuum beam (WLSC, 500 ∼ 720 nm) and a fundamental beam (798 nm) from a Ti:Sapphire laser. A reliable broadband NDTPA spectrum is acquired in a single-shot detection procedure using a 128-channel lock-in amplifier. The NDTPA spectra for several common laser dyes are measured. Two photon absorption cross section enhancements are found in the experiment and validated by theoretical calculation for all of the chromophores.
Highlights
Interest in materials that exhibit high optical nonlinearity has increased dramatically in recent years
This study demonstrates a measurement system for a non-degenerate two-photon absorption (NDTPA) spectrum
The twists in this peak-tracing line are due to residual chirp of the white-light super-continuum (WLSC) and its group velocity dispersion (GVD) in the solvent
Summary
Interest in materials that exhibit high optical nonlinearity has increased dramatically in recent years. Due to the diversification in the pulse duration during the pulse wavelength shifting, the pulse intensity changes for each measurement These methods are indirect ways to measure the TPA spectrum, and may suffer from other systematic errors related to the intermediate parameters, such as the collection efficiency of emitted fluorescence, fluorescence quantum efficiency, and so on.[7] the degenerate detection’s intensity squared dependence on the excitation beam intensity may lead to a large error during the square calculation.
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