Two-photon-absorption enhanced terahertz generation from KTP optically pumped in the visible-to-UV range
- 28 October 2021
- journal article
- research article
- Published by Optica Publishing Group in Optics Express
- Vol. 29 (23), 37683-37694
- https://doi.org/10.1364/oe.438597
Abstract
By generating terahertz pulses in KTP crystals through optical rectification with a pump photon energy varying from below to above the bandgap, we observe a peak of the THz signal at the bandgap energy but also a second one around half the bandgap. This later one is attributed to a two-photon absorption enhanced nonlinearity, which is validated by the similarity of the two-photon absorption coefficient and THz peak amplitude data versus the pump photon energy. A careful analysis of the KTP sample absorption spectral dependence nearby the bandgap demonstrates that KTP is an indirect bandgap crystal, whose absorption below the bandgap involves emission of a phonon related to the symmetric Ti-O stretching vibration, i.e. the ν1 (A1g) mode.Funding Information
- Knut och Alice Wallenbergs Stiftelse
- Stiftelsen Olle Engkvist Byggmästare
- Stiftelsen för Strategisk Forskning
- NATO Science for Peace (GS-5396)
- Agence Nationale de la Recherche (ANR-17-CE24-0031-01)
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