Spectral properties and effective upconverted lasing of new organic molecules
Introduction
Development of molecules with a large two-photon absorption cross-section has been a subject of great interest in recent years due to a variety of applications, including two-photon-excited fluorescence microscopy, three-dimensional optical data storage, infrared detector, optical limiting, short wavelength tunable laser, and fabrication of photonic band gap crystals 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18. Quantum chemical calculations indicate that substantial symmetric charge redistribution occurs upon excitation and provides large two-photon absorption [1]. Some basis of the concept for synthesis of molecules with large two-photon absorption cross-sections has been provided by theoretical studies 1, 19. One of the current important works is to synthesize stable molecules with large two-photon absorption cross-sections; and another current important work is the study of their chemical physical properties, which are of great importance to their application.
In this work, we synthesized a series of new organic molecules with large two-photon absorption cross-sections. Time-resolved spectroscopy experimental results demonstrate very fast emission dynamics in this kind of compound, which is an important characteristic for their application. For example, at the pumping of a 1.06 μ picosecond laser, the efficiency of two-photon-pumped lasing comes to 12.6%.
Section snippets
Experimental
The molecular structures of these upconverted emission molecules are shown in Fig. 1. The time-resolved single-photon absorption fluorescence has been measured with a frequency-doubled cw mode-locked Nd:YAG laser (Spectra-Physics Series 3000) as an excitation source, and a synchroscan streak camera (Hamamatsu Model C1587, 10 ps resolution) as a recorder. The spectral and temporal behaviors of two-photon-excited fluorescence have been measured with the fundamental wave of a single pulse
Results and discussion
The experimental results of the lifetimes (τ), linear absorption peak wavelengths (λAmax), peak wavelength (λEmax) of two-photon-excited fluorescence and the efficiency (η) of up-converted ASE (a passing of 1 cm cell) are shown in Table 1.
As shown in Table 1, the peak wavelengths of linear absorption of the new molecules are almost the same; and the peak wavelengths of two-photon-excited fluorescence of the new molecules are similar. Fig. 2 gives the spectra of two-photon-excited fluorescence
Acknowledgements
This work was supported by the State Key Program for Basic Research of China and National Natural Science Foundation of China.
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