Non-linear media in weakly curved spacetime: optical solitons and probe pulses for gravimetry

That light propagating in a gravitational field gets frequency-shifted is one of the basic consequences of any metric theory of gravity rooted in the equivalence principle. At the same time, also a time-dependent material's refractive index can frequency-shift light propagating in it. In this talk, we combine these two effects by showing that propagation in non-linear media in the presence of a refractive index perturbation leads to a gravity-dependent blueshift of light. This blueshift surpasses the gravitational redshift even if the medium is considered to be perfectly stiff and, in realistic scenarios, the amplification can be of several orders of magnitudes. We argue that this has the potential to facilitate optical sensing of small gravity gradients.