Investigation of inversion interferometry for superresolving point sources in optical microscopy

Modal imaging can provide unprecedented resolution for imaging point sources such as single-molecule fluorescent tags used to study biological samples. Theoretical work show that modal imaging can approach quantum limits of optical resolution of thermal point sources as quantified by Quantum Cramer Rao Bound [1], albeit assuming highly idealized measurements described by complex quantum operators. To utilize the potential of quantum measurements for superresolution microscopy it is imperative to understand the critical parameters in optical systems for realizing such quantum measurements under realistic conditions. Our efforts focus on understanding these critical parameters and developing an optical system for superresolving two incoherent point sources (i.e. fluorophore tags) for studying biological samples. We use a Mach-Zehnder interferometer with optical field inversion to realize image inversion interferometry, in principle allowing for near quantum-optimal measurement for imaging point sources. In our work, we combine inversion interferometry with florescence microscopy to image fluorescent beads acting as point sources. We investigate the performance of this technique and characterize the effects of aberrations and source bandwidth in the interference visibility. We plan to use this setup to realize superresolving measurements of single-molecule fluorescence and finally, protein dynamics in biological samples.

[1] M. Tsang, et al., Phys. Rev. X 6, 031033 (2016)