Towards high-sensitivity phase cancellation microscopy*

Label-free optical imaging techniques, such as light scattering and birefringence have long been used for detection of neural activity [1]. Wide-field interferometric microscopy has also been used for this purpose, most recently by Ling et al. [2]. Current interferometric systems are limited because of low phase measurement sensitivity of 10^-3, while a sensitivity of 10^-5 is necessary.
High sensitivity phase measurements will allow single-shot optical sensing of neural action potentials via imaging of optical path length changes. Here, we present a high phase sensitivity, phase cancellation interferometry system. We want to use a deformable mirror to generate a flat phase. A Wollaston prism is employed to split the beam into two orthogonally polarized beams with phase control. These beams are recombined for interferometric detection. A state-of-the-art 1.6M electron well-depth camera will be used for recordings. We report the analysis of our system’s sensitivity and compare it to theoretical predictions.

[1] Cohen et al. Nature, 1968. [2] Ling et al., Light: Science & Applications, 2018.