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At least 397 records · Page 22Linked to original sources
PubMed2006

Optical encryption using phase-shifting interferometry in a joint transform correlator.

We propose an optical encryption technique where the encrypted field and the decrypting key are obtained by three-step phase-shifting interferometry and registered as digital Fresnel holograms in a joint transform correlator architecture. Decryption can be achieved by digital or optical means. The technique allows the complete process to be achieved at high speed and data to be transfered via digital communication channels. Experimental implementation is performed in a system based on a programmable liquid-crystal TV display working in pure phase mode to represent the input data and to introduce the required phase shifts. A CCD is used to register the output data.

Journal Article↗
PubMed2006

Piston measurement by quadriwave lateral shearing interferometry.

We present what is to our knowledge a new method for measuring the relative piston between two independent beams separated by a physical gap, typical of petawatt facilities. The feasibility of this measurement, based on quadriwave lateral shearing interferometry, has been demonstrated experimentally: piston has been measured with accuracy and sensitivity better than 50 nm.

Journal Article↗
PubMed2006

Spectrally resolved phase-shifting interferometry for accurate group-velocity dispersion measurements.

We report an accurate method to measure the group-velocity dispersion (GVD) of transparent materials by use of spectrally resolved phase-shifting interferometry. The GVD of silica glass slide measured using an eight-step phase-shifting algorithm agrees well with that calculated using the Sellmeier dispersion equation over the entire visible wavelength region, with a rms error of < or =0.0036 microm(-2), better than that of other measurement methods reported so far.

Journal Article↗
PubMed2006

Highly sensitive, single-shot characterization for pulse widths from 0.4 to 85 ps using electro-optic shearing interferometry.

Single-shot characterization using electro-optic shearing interferometry (EOSI) is shown for pulse widths ranging from their transform limit (0.4 ps) to 200x their limit (85 ps). In EOSI, the spectral phase is reconstructed by interfering two spectrally sheared replicas of the pulse under test, where the shear is produced by applying linear temporal-phase modulation. We present a new reconstruction algorithm for accurately characterizing chirped pulses, even if the pulse extends beyond the linear region of the phase modulation. Furthermore, since EOSI does not rely on nonlinear optical processes, it requires only 1 nJ pulse energies for all pulse widths, corresponding to a single-shot sensitivity 1000x higher than previously demonstrated.

Journal Article↗
PubMed2006

Design of achromatic phase shifters for spaceborne nulling interferometry.

The designs of various achromatic phase shifters (APSs) envisaged for nulling interferometry and the search for extrasolar planets or systems from space are discussed in this Letter. It is shown that APS designs can sensibly influence the performance achieved by a simple Bracewell interferometer if they introduce a field of view (FoV) reversal and a pupil flip along one interferometer arm. Analytical and numerical simulations are presented, showing severe signal-to-noise ratio loss and a weak capacity for serendipitous discoveries. The use of FoV-reversal APS should therefore be restricted to the characterization of already known extrasolar planets rather than to their detection.

Journal Article↗
PubMed2004

Rapid, depth-resolved light scattering measurements using Fourier domain, angle-resolved low coherence interferometry.

We present a novel angle-resolved low coherence interferometry scheme for rapid measurement of depth-resolved angular scattering distributions to enable determination of scatterer size via elastic scattering properties. Depth resolution is achieved using a superluminescent diode in a modified Mach-Zehnder interferometer with the mixed signal and reference fields dispersed by an imaging spectrograph. The spectrograph slit is located in a Fourier transform plane of the scattering sample, enabling angle-resolved measurements over a 0.21 radian range. The capabilities of the new technique are demonstrated by recording the distribution of light scattered by a sub-surface layer of polystyrene microspheres in 40 milliseconds. The data are used to determine the microsphere size with good accuracy. Future clinical application to measuring the size of cell nuclei in living epithelial tissues using backscattered light is discussed.

Journal Article↗
PubMed2005

Nuclear morphology measurements using Fourier domain low coherence interferometry.

We present a new common path configuration Fourier domain low coherence interferometry (fLCI) optical system and demonstrate its capabilities by presenting results which determine the size of cell nuclei in a monolayer of T84 epithelial cells. The optical system uses a white light source in a modified Michelson interferometer and a spectrograph for detection of the mixed signal and reference fields. Depth resolution is obtained from the Fourier transform of the measured spectrum which provides the axial spatial cross-correlation between the signal and reference fields. The spectral dependence of scattering by the samples is determined by windowing the spectrum to measure the scattering amplitude as a function of wavenumber. We present evidence that fLCI accurately measures the longitudinal profile of cell nuclei rather than the transverse profile.

Journal Article↗
PubMed1994

Adsorption of a novel fluorescent derivative of a poly(ethylene oxide)/poly(butylene oxide) block copolymer on octadecyl glass studied by total internal reflection fluorescence and interferometry.

We have used total internal reflection fluorescence (TIRF) to measure the adsorption kinetics of a newly synthesized fluorescent derivative of a triblock copolymer comprising two poly(ethylene oxide) arms connected by a poly(butylene oxide) segment. The composition is (EO)400 (BO)55 (EO)400, in which EO represents ethylene oxide, BO represents butylene oxide, and one or both of the terminal OH groups of the two (EO)400 arms are labeled with tetramethylrhodamine. The poly(butylene oxide) segment binds to hydrophobic octadecyl glass, used as a substratum. The TIRF signal is shown to be derived almost entirely from surface-adsorbed polymer. This facilitates calculation of adsorption isotherms from 0.1-0.005% bulk polymer solution by means of diffusion kinetics. Information about the effective thickness of the adsorbed polymer, determined by optical interference microscopy, corresponds with what is known about the conformation of similar molecules at interfaces and indicates monolayer adsorption on the glass.

Adsorption↗
PubMed1992

Reflection electron microscopy and interferometry of atomic steps on gold and platinum single crystal surfaces.

Two beam interferences produced using an electrostatic biprism, which is inserted in the position of the selected area diaphragm of a commercial electron microscope, may be used in reflection electron microscopy to determine the phase shifts induced by structures on single crystal surfaces. A description of our interferometrical and holographical experiments on the phase shift at steps on (111)Au and (111)Pt single crystal surfaces is given and a straight forward interpretation of the results in terms of refraction will be discussed. As a particular result phase shifts of pi and 0.9 pi were measured for monatomic steps on (111)gold and (111)platinum surfaces, respectively.

Gold↗