Scalar approximation of Maxwell equations: derivation and accuracy.

Replacing Maxwell equations by a scalar wave equation is often used in computational imaging to simulate the light-sample interaction. It significantly reduces the computational burden but provides field maps that are insensitive to the polarization of the incident field, provided the latter is constant throughout the sample. Here, we develop a scalar approximation that accounts for the polarization of the incident field. Comparisons with rigorous simulations show that this approach is more accurate than the classical scalar approximation with similar computational cost.

Three-dimensional imaging with reflection synthetic confocal microscopy.

Biomedical imaging lacks label-free microscopy techniques able to reconstruct the contour of biological cells in solution, in 3D and with high resolution, as required for the fast diagnosis of numerous diseases. Inspired by computational optical coherence tomography techniques, we present a tomographic diffractive microscope in reflection geometry used as a synthetic confocal microscope, compatible with this goal and validated with the 3D reconstruction of a human effector T lymphocyte.

Versatile inversion tool for phaseless optical diffraction tomography.

Estimating three-dimensional complex permittivity of a sample from the intensity recorded at the image plane of a microscope for various angles of illumination, as in optical Fourier ptychography microscopy, permits one to avoid the interferometric measurements of classical tomographic diffraction microscopes (TDMs). In this work, we present a general inversion scheme for processing intensities that can be applied to any microscope configuration (transmission or reflection, low or high numerical aperture), scattering regime (single or multiple scattering), or sample-holder geometries (with or without substrate). The inversion procedure is tested on a wide variety of synthetic experiments, and the reconstructions are compared to that of TDMs. In most cases, phaseless data yield the same result as complex data, thus paving the way toward a drastic simplification of TDM implementation.

Versatile inversion tool for phaseless optical diffraction tomography: publisher's note.

This publisher's note corrects a typo in the title of J. Opt. Soc. Am. A36, C1 (2019)JOAOD60740-323210.1364/JOSAA.36.0000C1.

Multi-wavelength multi-angle reflection tomography.

We have developed a reflection tomographic microscope in which the sample is reconstructed from different holograms recorded under various angles and wavelengths of incidence. We present an iterative inversion algorithm based on a rigorous modeling of the wave-sample interaction that processes all the data simultaneously to estimate the sample permittivity distribution. We show that using several wavelengths permits a significant improvement of the reconstruction, especially along the optical axis.

Phase imaging and synthetic aperture super-resolution via total internal reflection microscopy.

Total internal reflection microscopy is mainly used in its fluorescence mode and is the reference technique to image fluorescent proteins in the vicinity of cell membranes. Here, we show that this technique can easily become a phase microscope by simply detecting the coherent signal resulting from the interference between the field scattered by the probed sample and the total internal reflection. Moreover, combining several illumination angles permits generating synthetic aperture reconstructions with improved resolutions compared to standard label-free microscopy techniques.

Superresolution with full-polarized tomographic diffractive microscopy.

Tomographic diffractive microscopy is a three-dimensional imaging technique that reconstructs the permittivity map of the probed sample from its scattered field, measured both in phase and in amplitude. Here, we detail how polarization-resolved measurements permit us to significantly improve the accuracy and the resolution of the reconstructions, compared to the conventional scalar treatments used so far. An isotropic transverse resolution of about 100 nm at a wavelength of 475 nm is demonstrated using this approach.

High-resolution tomographic diffractive microscopy in reflection configuration.

Tomographic diffractive microscopy (TDM) is a label-free imaging technique that reconstructs the 3D refractive index map of the probed object with an improved resolution compared to confocal microscopy. In this work, we consider a TDM implementation in which the sample is deposited on a reflective substrate. We show that this configuration requires calibration and inversion procedures that account for the presence of the substrate for getting highly resolved quantitative reconstructions.

Experimental demonstration of quantitative imaging beyond Abbe's limit with optical diffraction tomography.

Optical diffraction tomography (ODT) is a recent imaging technique that combines the experimental methods of phase microscopy and synthetic aperture with the mathematical tools of inverse scattering theory. We show experimentally that this approach permits us to obtain the map of permittivity of highly scattering samples with axial and transverse resolutions that are much better than that of a microscope with the same numerical aperture.

High efficiency silicon nitride surface grating couplers.

High efficiency surface grating couplers for silicon nitride waveguides have been designed, fabricated, and characterized. Coupling efficiencies exceeding 60 % are reported at a wavelength of 1.31 mum, as well as angular and wavelength -3 dB tolerances of 4 degrees and 50 nm, respectively. When the wavelength is increased from 1310 nm to 1450 nm the coupling efficiency progressively decreases but remains above 20 % at 1450 nm. The influence of the duty ratio of the grating has also been investigated: maximum coupling efficiency was obtained at 50 % duty ratio.

Balanced homodyne detection of Bragg microholograms in photopolymer for data storage.

Wavelength multiplexed holographic bit oriented memories are serious competitors for high capacity data storage systems. For data recording, two interfering beams are required whereas one of them should be blocked for readout in previously proposed systems. This makes the system complex. To circumvent this difficulty and make the device simpler, we validated an architecture for such memories in which the same two beams are used for recording and reading out. This balanced homodyne scheme is validated by recording holograms in a Lippmann architecture.

Homodyne detection readout for bit-oriented holographic memories.

Homodyne detection is proposed to increase the readout signal of bit-oriented holographic memories. It can be easily implemented on present memory architectures by making the diffracted signal interfere with a reflection of the reading beam. The large resulting increase of the readout signal can be used to enhance the data transfer rate. A first experimental demonstration of such a readout procedure is presented.