Lensless microscopy platform for single cell and tissue visualization.

Today, 3D imaging techniques are emerging, not only as a new tool in early drug discovery but also for the development of potential therapeutics to treat disease. Particular efforts are directed towards in vivo physiology to avoid perturbing the system under study. Here, we assess non-invasive 3D lensless imaging and its impact on cell behavior and analysis. We test our concept on various bio-applications and present here the first results. The microscopy platform based on in-holography provides large fields of view images (several mm2 compared to several hundred µm2) with sub-micrometer spatial resolution. 3D image reconstructions are achieved using back propagation functions post-processing.

Author Correction: All semiconductor enhanced high-harmonic generation from a single nanostructured cone.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Generating Ultrabroadband Deep-UV Radiation and Sub-10 nm Gap by Hybrid-Morphology Gold Antennas.

We experimentally investigate the interaction between hybrid-morphology gold optical antennas and a few-cycle Ti:sapphire laser up to ablative intensities, demonstrating rich nonlinear plasmonic effects and promising applications in coherent frequency upconversion and nanofabrication technology. The two-dimensional array of hybrid antennas consists of elliptical apertures combined with bowties in its minor axis. The plasmonic resonance frequency of the bowties is red-shifted with respect to the laser central frequency and thus mainly enhances the third harmonic spectrum at long wavelengths. The gold film between two neighboring elliptical apertures forms an hourglass-shaped structure, which acts as a "plasmonic lens" and thus strongly reinforces surface currents into a small area. This enhanced surface current produces a rotating magnetic field that deeply penetrates into the substrate. At resonant frequency, the magnetic field is further intensified by the bowties. The resonant frequency of the hourglass is blueshifted with respect to the laser central frequency. Consequently, it spectacularly extends the third harmonic spectrum toward short wavelengths. The resultant third harmonic signal ranges from 230 to 300 nm, much broader than the emission from a sapphire crystal. In addition, the concentration of surface current within the neck of the hourglass antenna results in a structural modification through laser ablation, producing sub-10 nm sharp metallic gaps. Moreover, after laser illumination the optical field hotspots are imprinted around the antennas, allowing us to confirm the subwavelength enhancement of the electric near-field intensity.

All semiconductor enhanced high-harmonic generation from a single nanostructured cone.

The enhancement and control of non-linear phenomena at a nanometer scale has a wide range of applications in science and in industry. Among these phenomena, high-harmonic generation in solids is a recent focus of research to realize next generation petahertz optoelectronic devices or compact all solid state EUV sources. Here, we report on the realization of the first nanoscale high harmonic source. The strong field regime is reached by confining the electric field from a few nanojoules femtosecond laser in a single 3D semiconductor waveguide. We reveal a strong competition between enhancement of coherent harmonics and incoherent fluorescence favored by excitonic processes. However, far from the band edge, clear enhancement of the harmonic emission is reported with a robust sustainability offering a compact nanosource for applications. We illustrate the potential of our harmonic nano-device by performing a coherent diffractive imaging experiment. Ultra-compact UV/X-ray nanoprobes are foreseen to have other applications such as petahertz electronics, nano-tomography or nano-medicine.

Spatially and spectrally resolved particle swarm optimization for precise optical property estimation using diffuse-reflectance spectroscopy.

This paper presents a new approach to estimate optical properties (absorption and scattering coefficients µa and µs) of biological tissues from spatially-resolved spectroscopy measurements. A Particle Swarm Optimization (PSO)-based algorithm was implemented and firstly modified to deal with spatial and spectral resolutions of the data, and to solve the corresponding inverse problem. Secondly, the optimization was improved by fitting exponential decays to the two best points among all clusters of the "particles" randomly distributed all over the parameter space (µs, µa) of possible solutions. The consequent acceleration of all the groups of particles to the "best" curve leads to significant error decrease in the optical property estimation. The study analyzes the estimated optical property error as a function of the various PSO parameter combinations, and several performance criteria such as the cost-function error and the number of iterations in the algorithms proposed. The final one led to error values between ground truth and estimated values of µs and µa less than 6%.