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16THz-I-2
NONLINEAR AND TERAHERTS PHOTONICS
^l^.ALT'22
Transmission features of nonlinear Fabry-Perot interferometer with giant Kerr nonlinearity in THz frequency range
S.A.Kozlov, A.A. Gendrina, M.D.Shipov, M.V.Melnik, A.N.Tsypkin
ITMO University, Saint Petersburg, Russian Federation Main author email address:tsypkinan@itmo.ru
Much attention has been paid to terahertz radiation in recent years. Features of THz radiationis quite surprising. For instance, relatively recently it was discovered that in the terahertz spectral range many materials demonstrate a giant low inertia nonlinearity, which ismuch larger than their nonlinearity in neighboring ranges[1-5].The report presents new data on the results of measuring the giant nonlinearity of materials with different methods. It is shown that according to the ratio of the magnitude of the nonlinear refractive index coefficient and the time of establishing a nonlinear response, materials with nonlinearity of avibrational nature in the terahertz spectral range demonstrate record values. This opens up new possibilities for terahertz nonlinear opticsand photonics.
For almost half a century, research has been carried out on optical bistability. It is a well-studied field, but there are still search for materials and systems that would allow the creation of near-ideal optical bistable devices. This report presents the results of the bistability features analysis of a nonlinear Fabry-Perot interferometer with media which refractive index nonlinearity is gigantic and low-inertia. It is shown that at high values of the radiation-induced change in the refractive index of the intracavity medium, its threshold length, at which bistable transmission is already observed, decreases significantly. At the same time, another threshold, small-scale smooth focusing, has not yet been reached. It is shown that the giant nonlinearity of the refractive index of the intracavity medium and the high value of its linear refractive index in the terahertz range make it possible to implement "resonatorless" nonlinear Fabry-Perot interferometers on solid-state plates with only Fresnel reflection. The figure shows the result of calculating the bistable transmission (dependence of the output intensity on the input one, )of terahertz radiation with a wavelength X = 1.2 mm by lithium niobate crystal plates of different thicknesses (1mm - curve a), 2.21mm - curve b), 0.52mm - curve c)).
a) b) c)
Fig. 1: Curves of bistable transmission of the mirrorless Fabry-Perot interferometer
The report discusses the results of an experimental study of the transmission of quasi-monochromatic terahertz radiation from gyrotrons by these plates.
[1]Artser I. et al. Radiation shift from triple to quadruple frequency caused by the interaction of terahertz pulses with a nonlinear Kerr medium //Scientific Reports. - 2022. - T. 12. - №. 1. - C. 1-8.
[2] Tcypkin A.N. et al. Giant Third-Order Nonlinear Response of Liquids at Terahertz Frequencies // Physical ReviewApplied. 2021. Vol. 15. №. 5. P. 054009.
[3] Zhukova M., Melnik M., Vorontsova I., Tcypkin A. & Kozlov S. Estimations of low-inertia cubic nonlinearity featuredby electro-optical crystals in the THz range//Photonics 7, 98 (2020).
[4] Tcypkin, A. N. et al. High Kerr nonlinearity of water in THz spectral range. Optics Express 27, 10419-10425 (2019).
[5] Dolgaleva K., Materikina D.V., Boyd R.W. & Kozlov S.A. Prediction of an extremely large nonlinear refractive indexfor crystals at terahertz frequencies//PhysicalReviev A 92, 023809 (2015).
