Doubling the field of view in off-axis low-coherence interferometric imaging

We present a new interferometric and holographic approach,named interferometry with doubled imaging area(IDIA),with which it is possible to double the camera field of view while performing off-axis interferometric imaging,without changing the imaging parameters,such as the magnification and the resolution.This technique enables quantitative amplitude and phase imaging of wider samples without reducing the acquisition frame rate due to scanning.The method is implemented using a compact interferometric module that connects to a regular digital camera,and is useful in a wide range of applications in which neither the field of view nor the acquisition rate can be compromised.Specifically,the IDIA principle allows doubling the off-axis interferometric field of view,which might be narrower than the camera field of view due to low-coherence illumination.We demonstrate the proposed technique for scan-free quantitative optical thickness imaging of microscopic biological samples,including live neurons and a human sperm cell in rapid motion under high magnification.In addition,we used the IDIA principle to perform non-destructive profilometry during a rapid lithography process of transparent structures.

Prediction of photothermal phase signatures from arbitrary plasmonic nanoparticles and experimental verification

We present a new approach for predicting spatial phase signals originating from photothermally excited metallic nanoparticles of arbitrary shapes and sizes.The heat emitted from such a nanoparticle affects the measured optical phase signal via changes in both the refractive index and thickness of the nanoparticle surroundings.Because these particles can be bio-functionalized to bind certain biological cell components,they can be used for biomedical imaging with molecular specificity,as new nanoscopy labels,and for photothermal therapy.Predicting the ideal nanoparticle parameters requires a model that computes the thermal and phase distributions around the particle,thereby enabling more efficient phase imaging of plasmonic nanoparticles and avoiding trial-and-error experiments while using unsuitable nanoparticles.The proposed nonlinear model is the first to enable the prediction of phase signatures from nanoparticles with arbitrary parameters.The model is based on a finite-volume method for geometry discretization and an implicit backward Euler method for solving the transient inhomogeneous heat equation,followed by calculation of the accumulative phase signal.To validate the model,we compared its results with experimental results obtained for gold nanorods of various concentrations,which we acquired using a custom-built wide-field interferometric phase microscopy system.