High-resolution-scanning waveguide microscopy: spatial refractive index and topography quantification.

We report on a high-resolution metal-clad waveguide scanning microscopic method with a diffraction-limited resolution. This microscope can be operated in both TM and TE waveguide modes with radially and azimuthally polarized beams, respectively, and allows both refractive index and topography of dielectric objects to be evaluated at high resolution and sensitivity. We emphasize the performance of this microscopic method from calibrated 3D polymer microstructures with rectangular, disk, and ring shapes.

Revealing stiffening and brittling of chronic myelogenous leukemia hematopoietic primary cells through their temporal response to shear stress.

Cancer cell transformation is often accompanied by a modification of their viscoelastic properties. When capturing the stress-to-strain response of primary chronic myelogenous leukemia (CML) cells, from two data sets of CD34+ hematopoietic cells isolated from healthy and leukemic bone marrows, we show that the mean shear relaxation modulus increases upon cancer transformation. This stiffening of the cells comes along with local rupture events, detected as reinforced sharp local maxima of this modulus, suggesting that these cancer cells respond to a local mechanical stress by a cascade of local brittle failure events.

Wavelet-based decomposition of high resolution surface plasmon microscopy V(Z) curves at visible and near infrared wavelengths.

Surface plasmon resonance is conventionally conducted in the visible range and, during the past decades, it has proved its efficiency in probing molecular scale interactions. Here we elaborate on the first implementation of a high resolution surface plasmon microscope that operates at near infrared (IR) wavelength for the specific purpose of living matter imaging. We analyze the characteristic angular and spatial frequencies of plasmon resonance in visible and near IR lights and how these combined quantities contribute to the V(Z) response of a scanning surface plasmon microscope (SSPM). Using a space-frequency wavelet decomposition, we show that the V(Z) response of the SSPM for red (632.8 nm) and near IR (1550 nm) lights includes the frequential response of plasmon resonance together with additional parasitic frequencies induced by the objective pupil. Because the objective lens pupil profile is often unknown, this space-frequency decomposition turns out to be very useful to decipher the characteristic frequencies of the experimental V(Z) curves. Comparing the visible and near IR light responses of the SSPM, we show that our objective lens, primarily designed for visible light microscopy, is still operating very efficiently in near IR light. Actually, despite their loss in resolution, the SSPM images obtained with near IR light remain contrasted for a wider range of defocus values from negative to positive Z values. We illustrate our theoretical modeling with a preliminary experimental application to blood cell imaging.

Amplitude and phase images of cellular structures with a scanning surface plasmon microscope.

Imaging cellular internal structure at nanometer scale axial resolution with non invasive microscopy techniques has been a major technical challenge since the nineties. We propose here a complement to fluorescence based microscopies with no need of staining the biological samples, based on a Scanning Surface Plasmon Microscope (SSPM). We describe the advantages of this microscope, namely the possibility of both amplitude and phase imaging and, due to evanescent field enhancement by the surface plasmon resonance, a very high resolution in Z scanning (Z being the axis normal to the sample). We show for fibroblast cells (IMR90) that SSPM offers an enhanced detection of index gradient regions, and we conclude it is very well suited to discriminate regions of variable density in biological media such as cell compartments, nucleus, nucleoli and membranes.

Near-field probing of active photonic-crystal structures.

We report a study of the optical near field of an active integrated component operating near the 1.55-mum telecommunications wavelength. The device is based on a two-dimensional photonic crystal etched in a suspended InP membrane. Topographic as well as optical information is collected by use of a scanning near-field optical microscope in collection mode, providing information about the local distribution of the losses.