Highly Efficient Sum‐Frequency Generation in Niobium Oxydichloride NbOCl2 Nanosheets

Parametric infrared (IR) upconversion is a process in which low‐frequency IR photons are upconverted into high‐frequency ultraviolet/visible photons through a nonlinear optical process. It is of paramount importance for a wide range of security, material science, and healthcare applications. However...

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Bibliographic Details
Published in:Advanced optical materials 2023-04, Vol.11 (7), p.n/a
Main Authors: Abdelwahab, Ibrahim, Tilmann, Benjamin, Zhao, Xiaoxu, Verzhbitskiy, Ivan, Berté, Rodrigo, Eda, Goki, Wilson, William L., Grinblat, Gustavo, S. Menezes, Leonardo, Loh, Kian Ping, Maier, Stefan A.
Format: Article
Language:English
Subjects:
2D materials
cross‐correlation
Crystal structure
Excitation
ferroelectricity
Layered materials
Materials science
Nanosheets
Niobium
Nonlinear optics
optical nonlinearity
Optics
Penetration depth
Photons
Second harmonic generation
sum‐frequency generation
Upconversion
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Summary:Parametric infrared (IR) upconversion is a process in which low‐frequency IR photons are upconverted into high‐frequency ultraviolet/visible photons through a nonlinear optical process. It is of paramount importance for a wide range of security, material science, and healthcare applications. However, in general, the efficiencies of upconversion processes are typically extremely low for nanometer‐scale materials due to the short penetration depth of the excitation fields. Here, parametric IR upconversion processes, including frequency doubling and sum‐frequency generation, are studied in layered van der Waals NbOCl2. An upconversion efficiency of up to 0.004% is attained for the NbOCl2 nanosheets, orders of magnitude higher than previously reported values for nonlinear layered materials. The upconverted signal is sensitive to layer numbers, crystal orientation, excitation wavelength, and temperature, and it can be utilized as an optical cross‐correlator for ultrashort pulse characterization. Extremely large second‐order optical responses (second‐harmonic generation, sum‐frequency generation [SFG]) are reported for NbOCl2 nanosheets in the UV/vis range with a measured absolute conversion efficiency of 0.004%. The nonlinear signal varies strongly with thickness, crystal orientation, excitation wavelength, and temperature. The time‐resolved SFG signal within the thin NbOCl2 sheet is utilized as a nanosized intensity cross‐correlator for measuring ultrashort pulse durations.
ISSN:2195-1071
2195-1071
DOI:10.1002/adom.202202833