Dresden 2020 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 61: Focus Session: Tailored Nonlinear Photonics I
HL 61.4: Talk
Thursday, March 19, 2020, 10:45–11:00, POT 51
Systematic Investigation of the Nondegenerate Two-Photon Absorption Coefficient in ZnSe — •Laura Krauss-Kodytek, Claudia Ruppert, and Markus Betz — Experimentelle Physik 2, Technische Universität Dortmund, Otto-Hahn-Straße 4a, 44227 Dortmund, Germany
The two-photon absorption (TPA) coefficient βTPA is strongly enhanced in case of extremely nondegenerate photon pairs (ℏω1≠ℏω2) when compared to the degenerate case (ℏω1=ℏω2) [1]. However, a systematic study of the TPA strength as a function of the involved photon pair’s energy ratio ω1/ω2 remains elusive.
To investigate this dependence we use an optical parametrical amplifier which provides photon pairs within energy ratios from unity to 3.5. The photon pair’s sum energy of 3.1 eV slightly exceeds the bandgap of ZnSe (Eg=2.7 eV at room temperature). The ZnSe samples have a thickness of 40 µm and a (100)- or (110)-orientation.
The setup is designed in a pump-probe fashion and the peak signals at time overlap reflect the TPA strength βTPA. We observe an enormous increase of the nondegenerate TPA strength compared to the degenerate one. Further, the measured trend of the βTPA as a function of the energy ratio is well in line with the theoretical predictions [2].
[1] D. Fishman et al., Nature Photonics 5, 561-565 (2011)
[2] W.-R. Hannes and T. Meier, Physical Review B 99, 125301 (2019)