Breaking Abbe's diffraction limit with harmonic deactivation microscopy

TL;DR

HADES is a novel nonlinear microscopy technique that achieves sub-100 nm resolution without fluorescent labels by controlling harmonic generation at the quantum level, enabling super-resolution imaging in label-free samples.

Contribution

Introduction of harmonic deactivation microscopy (HADES), a new method to surpass the diffraction limit in nonlinear microscopy without requiring fluorescent labeling.

Findings

Resolution improves with higher harmonic orders.

Deactivation limited by maximum deactivation-pulse fluence.

Potential for sub-100 nm resolution in regular nonlinear microscopes.

Abstract

Nonlinear optical microscopy provides elegant means for label-free imaging of biological samples and condensed matter systems. The widespread areas of application could even be increased if resolution was improved, which is currently limited by the famous Abbe diffraction limit. Super-resolution techniques can break the diffraction limit but rely on fluorescent labeling. This makes them incompatible with (sub-)femtosecond temporal resolution and applications that demand the absence of labeling. Here, we introduce harmonic deactivation microscopy (HADES) for breaking the diffraction limit in non-fluorescent samples. By controlling the harmonic generation process on the quantum level with a second donut-shaped pulse, we confine the third harmonic generation to three times below the original focus size and use this pulse for scanning microscopy. We demonstrate that resolution improvement by deactivation is more efficient for higher harmonic orders, and only limited by the maximum applicable deactivation-pulse fluence. This provides a route towards sub-100~nm resolution in a regular nonlinear microscope. The new capability of label-free super-resolution can find immediate applications in condensed matter physics, semiconductor metrology, and biomedical imaging.