| Abstract: |
A four-level $N$-scheme with a two-mode active-Raman-gain-core is investigated for large and rapidly-responding Kerr effect enhancement at room-temperature. The new scheme is fundamentally different from electromagnetically-induced-transparency (EIT)-based ultra-slow-wave Kerr effect enhancement scheme. It eliminates the requirement of group velocity matching and multi-specie medium. It also eliminates significant probe field attenuation or distortion associated with weakly-driven EIT-based schemes. We show that a probe field can acquire a large, frequency tunable, gain-assisted nonlinear phase shift and yet travel with gain-assisted {\em superluminal} propagation velocity. This raises the possibility of rapidly-responding, frequency tunable nonlinear phase switching and phase gates for information science. |
