What is it about?
Semiconductors such as gallium phosphide, gallium arsenide, and silicon are important electronic materials, but also have increasing applications in photonics. Two-photon absorption (2PA) of light in these materials can be an unwanted side effect in the propagation of light over long distances or high intensity in fiber optics or can be exploited for practical applications such as in all-optical switches or exciting photoluminescence in semiconductor quantum dots for confocal microscopy. 2PA can also reveal complementary information about the electronic band structure in these materials from one-photon absorption due to the sometimes mutually exclusive selection rules. We have measured the magnitude and rotational anisotropy of the 2PA coefficient in these semiconductors over a broad spectral range near their 2PA band edges. We also report observed anomalies and discuss their possible origins.
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Why is it important?
We report 2PA spectra in these materials measured in a pump-probe scheme, which can demonstrate in-situ whether the nonlinear loss is due to 2PA or other effects in order to screen out measurements which may be complicated by effects such as free-carrier absorption, various nonlinear gratings, and non-instantaneous (history-dependent) processes. This is not straightforward to do in single-beam experiments and can lead to wide ranges in the reported 2PA coefficient. We also report the magnitude and anisotropy of 2PA over a broad spectral range, which is useful for developing ab initio theories and for understanding the magnitude of the effect when it is either undesired (such as in fiber optics), or desired (such as in all-optical switching).
Perspectives
This work is the culmination of a 2+ year collaboration with my co-authors at CIO in Leon, Mexico, and it was a great pleasure to travel there to work with them and perform this experiment. The amount of learning that occurred during the experimental phase, as well as the data analysis and writing of this article once I returned to Texas, was tremendous. I hope that the experimental results, the comparisons to existing literature, and extensive supplementary material in this article will prove useful to those in the field.
Dr. Brandon Joseph Furey
Universitat Innsbruck
Read the Original
This page is a summary of: Im{χ(3)} spectra of 110-cut GaAs, GaP, and Si near the two-photon absorption band edge, Journal of Applied Physics, May 2021, American Institute of Physics,
DOI: 10.1063/5.0047478.
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