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Optics Express Aug 2006In this paper, we introduce a new form of cross-sectional, coherence-gated fluorescence imaging, which we term 'spectral-domain fluorescence coherence tomography'...
In this paper, we introduce a new form of cross-sectional, coherence-gated fluorescence imaging, which we term 'spectral-domain fluorescence coherence tomography' (SD-FCT). SD-FCT is accomplished by spectrally detecting self-interference of the spontaneous emission of fluorophores located along the axial (depth) dimension of the sample. We have built a first generation SD-FCT system that utilizes two opposing low numerical-aperture objective lenses in an interferometer and an imaging spectrometer for detecting self-interference of fluorescence emitted from a sample. Here, in proof-of-principle experiments we demonstrate cross-sectional profiling of layered fluorescence phantoms. Narrow (a few micrometers FWHM) axial point-spread functions, large ranging depths (a few hundreds of micrometers) and wide fields of view (>1 mm) were measured. Initial results suggest that SD-FCT may be a viable tool for the investigation of semi-transparent and selectively labeled fluorescent samples.
Topics: Equipment Design; Fluorescence; Fourier Analysis; Image Processing, Computer-Assisted; Interferometry; Spectrometry, Fluorescence
PubMed: 19529084
DOI: 10.1364/oe.14.007134 -
Acta Crystallographica. Section D,... Jan 2015Over the last decades, a wide range of biophysical techniques investigating protein-ligand interactions have become indispensable tools to complement high-resolution...
Over the last decades, a wide range of biophysical techniques investigating protein-ligand interactions have become indispensable tools to complement high-resolution crystal structure determinations. Current approaches in solution range from high-throughput-capable methods such as thermal shift assays (TSA) to highly accurate techniques including microscale thermophoresis (MST) and isothermal titration calorimetry (ITC) that can provide a full thermodynamic description of binding events. Surface-based methods such as surface plasmon resonance (SPR) and dual polarization interferometry (DPI) allow real-time measurements and can provide kinetic parameters as well as binding constants. DPI provides additional spatial information about the binding event. Here, an account is presented of new developments and recent applications of TSA and DPI connected to crystallography.
Topics: Calorimetry; Interferometry; Ligands; Proteins
PubMed: 25615858
DOI: 10.1107/S1399004714016617 -
Optics Express Nov 2014The paper presents a novel algorithm based on digital holographic interferometry and being promising for evaluation of phase variations from highly noisy or modulated by...
The paper presents a novel algorithm based on digital holographic interferometry and being promising for evaluation of phase variations from highly noisy or modulated by speckle-structures digital holograms. The suggested algorithm simulates an interferogram in finite width fringes, by analogy with classical double exposure holographic interferometry. Thus obtained interferogram is then processed as a digital hologram. The advantages of the suggested approach are demonstrated in numerical experiments on calculations of differences in phase distributions of wave fronts modulated by speckle structure, as well as in a physical experiment on the analysis of laser-induced heating dynamics of an aqueous solution of a photosensitizer. It is shown that owing to the inherent capability of the approach to perform adjustable smoothing of compared wave fronts, the resulting difference undergoes noise filtering. This capability of adjustable smoothing may be used to minimize losses in spatial resolution. Since the method allows to vary an observation angle of compared wave fields, an opportunity to compensate misalignment of optical axes of these wave fronts arises. This feature can be required, for example, when using two different setups in comparative digital holography or for compensation of recording system displacements during a set of exposures in studies of dynamic processes.
Topics: Algorithms; Holography; Interferometry; Light; Signal Processing, Computer-Assisted
PubMed: 25402078
DOI: 10.1364/OE.22.028363 -
Optics Express Feb 2019We report the development and characterisation of highly miniaturised fibre-optic sensors for simultaneous pressure and temperature measurement, and a compact...
We report the development and characterisation of highly miniaturised fibre-optic sensors for simultaneous pressure and temperature measurement, and a compact interrogation system with a high sampling rate. The sensors, which have a maximum diameter of 250 µm, are based on multiple low-finesse optical cavities formed from polydimethylsiloxane (PDMS), positioned at the distal ends of optical fibres, and interrogated using phase-resolved low-coherence interferometry. At acquisition rates of 250 Hz, temperature and pressure changes of 0.0021 °C and 0.22 mmHg are detectable. An in vivo experiment demonstrated that the sensors had sufficient speed and sensitivity for monitoring dynamic physiological pressure waveforms. These sensors are ideally suited to various applications in minimally invasive surgery, where diminutive lateral dimensions, high sensitivity and low manufacturing complexities are particularly valuable.
Topics: Equipment Design; Fiber Optic Technology; Interferometry; Optical Fibers; Pressure; Temperature; Transducers
PubMed: 30876162
DOI: 10.1364/OE.27.005641 -
Optics Express Jul 2013We investigate the performances of a silicon PN-junction Mach-Zehnder modulator for analog application. The slope efficiency and spurious-free dynamic range (SFDR) of...
We investigate the performances of a silicon PN-junction Mach-Zehnder modulator for analog application. The slope efficiency and spurious-free dynamic range (SFDR) of such a modulator upon carrier depletion and carrier injection effects are characterized and compared. Input RF frequency-dependence measurements show that the depletion-type modulator is usually with ~20 dB ∙ Hz(2/3) higher SFDR comparing to the injection-type modulator, yet with an order-of-magnitude lower slope efficiency. For the depletion-type and injection-type modulators, the measured maximum SFDRs are respectively ~95 dB ∙ Hz(2/3) and 75 dB∙Hz(2/3), with maximum slope efficiency of 0.3 V(-1) and 8 V(-1<). We numerically model the SFDR by using the experimentally extracted effective refractive index change, which shows good agreement with the measurements.
Topics: Equipment Design; Equipment Failure Analysis; Interferometry; Refractometry; Semiconductors; Telecommunications
PubMed: 23938508
DOI: 10.1364/OE.21.016570 -
Proceedings of the National Academy of... Apr 2009Freestanding phospholipid bilayers have been assembled spanning shallow, micrometer-sized wells etched into a Si wafer substrate so that the bilayers are near (within...
Freestanding phospholipid bilayers have been assembled spanning shallow, micrometer-sized wells etched into a Si wafer substrate so that the bilayers are near (within hundreds of nanometers) but not in contact with the wafer surface. The proximity of the bilayers to the highly reflective Si/SiO(2) interface allows them to be probed by using fluorescence-interference techniques. These interferometry measurements show that the bilayers are curved and that the curvature can be varied by changes in osmotic pressure. Furthermore, the ionophore gramicidin can be incorporated into the bilayers, making them selectively permeable to monovalent cations. This freestanding architecture may overcome surface-interaction problems that occur when cell membrane proteins are introduced into solid supported bilayers, while also allowing for high-precision measurements of changes in fluorophore position by interferometry.
Topics: Cell Membrane; Fluorescence; Gramicidin; Interferometry; Lipid Bilayers; Methods; Osmotic Pressure; Silicon; Silicon Dioxide
PubMed: 19307575
DOI: 10.1073/pnas.0901770106 -
Scientific Reports Mar 2014The emergent self-organization of a neuronal network in a developing nervous system is the result of a remarkably orchestrated process involving a multitude of chemical,...
The emergent self-organization of a neuronal network in a developing nervous system is the result of a remarkably orchestrated process involving a multitude of chemical, mechanical and electrical signals. Little is known about the dynamic behavior of a developing network (especially in a human model) primarily due to a lack of practical and non-invasive methods to measure and quantify the process. Here we demonstrate that by using a novel optical interferometric technique, we can non-invasively measure several fundamental properties of neural networks from the sub-cellular to the cell population level. We applied this method to quantify network formation in human stem cell derived neurons and show for the first time, correlations between trends in the growth, transport, and spatial organization of such a system. Quantifying the fundamental behavior of such cell lines without compromising their viability may provide an important new tool in future longitudinal studies.
Topics: Biological Transport; Cell Differentiation; Cells, Cultured; Humans; Interferometry; Lithium Chloride; Models, Neurological; Nerve Net; Neurons; Stem Cells
PubMed: 24658536
DOI: 10.1038/srep04434 -
Analytical Chemistry Jan 2012
Review
Topics: Animals; DNA; Humans; Immunoassay; Interferometry; Proteins; Surface Plasmon Resonance
PubMed: 22060037
DOI: 10.1021/ac202812h -
Journal of Biomedical Optics 2008We demonstrate that microscopic imaging is feasible in ultrasound-modulated optical tomography (UOT) of soft biological tissues, using a high-frequency focused...
We demonstrate that microscopic imaging is feasible in ultrasound-modulated optical tomography (UOT) of soft biological tissues, using a high-frequency focused ultrasound transducer with a 75-MHz central frequency. Our experiments in tissue mimicking phantoms show that at an imaging depth of about 2 mm, an axial resolution better than 30 microm can be achieved, whereas the lateral resolution is 38 microm. A long-cavity scanning confocal Fabry-Perot interferometer (CFPI) is used for real-time detection of multiply scattered light modulated by high-frequency ultrasound pulses propagating in an optically scattering medium. We also compare the performances of various high-frequency focused ultrasound transducers with central frequencies of 15 MHz, 30 MHz, 50 MHz, and 75 MHz. The comparison is based on two-dimensional (2-D) images of optically absorbing objects positioned at a few millimeters depth below the surface of both optically scattering phantoms and soft biological tissue samples. Our experimental results show that modulation depth and image contrast decrease with an increase in ultrasound frequency. In addition, we use analytical calculations to show that modulation depth decreases with increasing ultrasound frequency.
Topics: Computer-Aided Design; Equipment Design; Equipment Failure Analysis; Image Enhancement; Interferometry; Microscopy, Acoustic; Phantoms, Imaging; Reproducibility of Results; Sensitivity and Specificity
PubMed: 19021426
DOI: 10.1117/1.2983671 -
Science Advances Jun 2016Light microscopes can detect objects through several physical processes, such as scattering, absorption, and reflection. In transparent objects, these mechanisms are...
Light microscopes can detect objects through several physical processes, such as scattering, absorption, and reflection. In transparent objects, these mechanisms are often too weak, and interference effects are more suitable to observe the tiny refractive index variations that produce phase shifts. We propose an on-chip microscope design that exploits birefringence in an unconventional geometry. It makes use of two sheared and quasi-overlapped illuminating beams experiencing relative phase shifts when going through the object, and a complementary metal-oxide-semiconductor image sensor array to record the resulting interference pattern. Unlike conventional microscopes, the beams are unfocused, leading to a very large field of view (20 mm(2)) and detection volume (more than 0.5 cm(3)), at the expense of lateral resolution. The high axial sensitivity (<1 nm) achieved using a novel phase-shifting interferometric operation makes the proposed device ideal for examining transparent substrates and reading microarrays of biomarkers. This is demonstrated by detecting nanometer-thick surface modulations on glass and single and double protein layers.
Topics: Equipment Design; Microscopy, Interference; Microscopy, Phase-Contrast; Molecular Imaging; Sensitivity and Specificity
PubMed: 27386571
DOI: 10.1126/sciadv.1600077