Spatial polarization gating of high-harmonic generation in solids

High-harmonic generation from solids can be utilized as a probe of ultrafast dynamics, but thus far only over extended sample areas, since its spatial resolution is diffraction limited. Here, we propose spatial polarization gating, that is, using a spatially varying ellipticity of a driving laser pulse to reduce the spatial profile of high-harmonic emission below the diffraction limit and hence increase spatial resolution. We show experimentally and by numerical simulations that our method is generally applicable as suppressing high harmonics in elliptical fields is a common response in all solids. We also briefly explore the possibility of applying this technique to wide-field imaging, specifically to nonlinear structured illumination microscopy. Our findings indicate that spatial polarization gating can enable all-optical femto-to-attosecond label-free imaging beyond the Abbe limit.