Parametric Amplification of Optical Pulses through Synthetic Motion in a Time-Varying Medium.

Yaswant Vaddi, Theng-Loo Lim, Yiyu Zhou, Mohammad Karimi, Shivashankar Vangala, Jeremy Upham, Joshua R Hendrickson, Robert W Boyd, M Zahirul Alam

Parametric amplification of optical waves conventionally requires phase matching and frequency offsets between interacting beams. Here, we demonstrate a fundamentally different amplification mechanism in epsilon-near-zero (ENZ) materials, where intense optical pumping creates a time-varying medium. We show, both theoretically and experimentally, that large spatiotemporal index modulations enable parametric amplification of frequency-degenerate pulses without requiring chirp or frequency offsets. The gain scales quadratically rather than linearly with the product of the pump intensity and the nonlinear refractive index coefficient

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