# Publication Citation: Large and Rapidly-Responding Kerr Nonlinear Phase Shift Using a Four-Level $N$-Scheme With an Active Raman Gain Core

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Author(s): Lu Deng; Edward W. Hagley; Kaijun Jiang; M Payne; Large and Rapidly-Responding Kerr Nonlinear Phase Shift Using a Four-Level $N$-Scheme With an Active Raman Gain Core Date Unknown Using a lifetime broadened $N$-scheme with an active-Raman-gain (ARG) $\Lambda$ core we show that large nonlinear phase shift can be induced without signal wave attenuation. The new scheme is not based on the ultra-slow-wave technique and it does not exhibit the signal wave attenuation or distortion associated with weakly-driven electromagnetically-induced-transparency-based schemes. We show that the signal wave acquires a large nonlinear phase shift and travels with {\em superluminal} propagation characteristics. This raises the possibility of rapidly responding nonlinear phase switching and phase gates for information science. Optics Letters fast phase gate;gain medium;Kerr nonlinear phase shift