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arXiv:1505.05845 · Physical Review B

Kerr coefficients of plasma resonances in Josephson junction chains

Thomas Weißl, Bruno Küng, Étienne Dumur, Alexey K. Feofanov, I. Matei, Cécile Naud, O. Buisson, F. W. J. Hekking, Wiebke Guichard

Published Sep 14, 2015• 85 citations
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Abstract

We present an experimental and theoretical analysis of the self- and cross-Kerr effect of extended plasma resonances in Josephson junction chains. We calculate the Kerr coefficients by deriving and diagonalizing the Hamiltonian of a linear circuit model for the chain and then adding the Josephson nonlinearity as a perturbation. The calculated Kerr coefficients are compared with the measurement data of a chain of 200 junctions. The Kerr effect manifests itself as a frequency shift that depends linearly on the number of photons in a resonant mode. By changing the input power on a low signal level, we are able to measure this shift. The photon number is calibrated using the self-Kerr shift calculated from the sample parameters. We then compare the measured cross-Kerr shift with the theoretical prediction, using the calibrated photon number.

DOI
10.1103/physrevb.92.104508

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The self-Kerr-nonlinearity of a four-level N\mathsf{N}N-type atomic system is studied both experimentally and theoretically. The self-Kerr-nonlinear coefficient n2{n}_{2}n2​ of the probe beam is greatly enhanced near atomic resonance, and can be dramatically modified by changing the switching laser power. With an increasing switching laser power, the slope of the Kerr nonlinear coefficient n2{n}_{2}n2​ around the atomic resonance changes from negative to positive, and the value of n2{n}_{2}n2​ varies from \ensuremath{\sim}--4 \ifmmode\times\else\texttimes\fi{} 10${}^{\ensuremath{-}6}$ to 4 \ifmmode\times\else\texttimes\fi{} 10${}^{\ensuremath{-}6}$ cm2{}^{2}2/W at certain near-resonant probe frequency detunings. Such controllable Kerr nonlinearity can find applications in optoelectronic devices, such as all-optical switching and logic gates.
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