Browsing by Author "Ullrich, B."

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    The influence of self-absorption on the photoluminescence of thin film CdS demonstrated by two-photon absorption
    Ullrich, B.; Schroeder, R.; Graupner, W.; Sakai, H. (Optical Society of America, 2001-07)
    By means of two-photon excited photoluminescence, we demonstrate the influence of self-absorption on the emission properties of thin (1.5 mum) film CdS formed by laser ablation. The excitation of the sample is performed with 200 fs pulses at 804 nm (1.54 eV). The photoluminescence spectrum takes the form of a single peak centered at 510 nm (2.43 eV) at 300 K. The spectrum is shifted about 45 meV to lower energies with respect to the photoluminescence excited by one photon absorption. By fitting the photoluminescence spectra with the Roosbroeck-Shockley relation and Urbach's rule, it is shown by Beer's law that the shift is caused by self-absorption. The results further provide evidence of low impurity concentration and excellent surface quality. They also confirm the outstanding optical properties of thin film CdS formed by pulsed-laser deposition and suggest the application of the films for effective up-conversation materials in ultra-fast experiments. (C) 2001 Optical Society of America.
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    Two-photon-excited green emission and its dichroic shift of oriented thin-film CdS on glass formed by laser deposition
    Ullrich, B.; Schroeder, R.; Sakai, H.; Zhang, A.; Cheng, S. Z. D. (AIP Publishing, 2002-01)
    The photoluminescence of oriented thin-film CdS on glass formed by laser deposition was investigated employing 200 fs, 1.54 eV laser pulses at room temperature. The ultrafast excitation caused a two-photon absorption process, which results in purely green emission at the band gap. The spectra are fitted very well by the application of the van Roosbroeck-Shockley relation, density of states, and Urbach's rule demonstrating the intrinsic character of the radiative recombination. It is further shown that the energy position of the emission peak depends on the polarization of the impinging laser beam due to the dichroism of the highly oriented films. (C) 2002 American Institute of Physics.