Publications by Theo Lasser | EPFL Graph Search

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We designed a fluorescence correlation spectroscopy (FCS) system for measurements on surfaces. The system consists of an objective-type total internal reflection fluorescence (TIRF) microscopy setup, adapted to measure FCS. Here, the fluorescence exciting ...

Fourier domain Optical coherence microscopy (FDOCM) offers excellent sensitivity and high axial resolution to image the structure of biological tissue. The depth information is extracted in parallel and allows very high volume acquisition rates. An illumination scheme employing an axicon lens produces a Bessel-like interference pattern to obtain a laterally highly confined illumination needle, extending over a long axial range. High lateral resolution is provided over an extended depth of field (xf). For in

We present an application of massively parallel processing of quantitative flow measurements data acquired using spectral optical coherence microscopy (SOCM). The need for massive signal processing of these particular datasets has been a major hurdle for m ...

Fluorescence localization microscopy (i.e., PALM, STORM) has enabled optical imaging at nanometer-scale resolutions. The localization algorithms used in these techniques rely on fitting a 2-D Gaussian to the in-focus image of individual fluorophores. For f ...

We present a rapid and flexible framework for the accurate calculation of the detection efficiency of fluorescence emission in isotropic media as well as in the vicinity of dielectric or metallic interfaces. The framework accounts for the dipole characteri ...

Recently, we have experimentally demonstrated a new form of cross-sectional, coherence-gated fluorescence imaging referred to as SD-FCT (‘spectral-domain fluorescence coherence tomography’). Imaging in SD-FCT is accomplished by spectrally detecting self-in ...

Laser Doppler Imaging (LDI) is a non-invasive optical technique used for assessing the blood flow in biological tissue. This technique allows visualizing 2D distribution of blood flow over an extended area of tissue, e.g. human skin. We have developed a new high-speed instrument for full-field blood flow laser Doppler imaging. The new imager delivers high-resolution flow images every 0.7 to 11 seconds, depending on the number of points in the acquired time-domain signal (32-512 points) and the image resolut

Many solutions have been proposed to produce phase quantitative images of biological cell samples. Among these, Spectral Domain Phase Microscopy combines the fast imaging speed and high sensitivity of Optical Coherence Microscopy (OCM) in the Fourier domain with the high phase stability of common-path interferometry. We report on a new illumination scheme for OCM that enhances the sensitivity for backscattered light and detects the weak sample signal, otherwise buried by the signal from specular reflection.

We present a new model of optical coherence tomography (OCT) taking into account multiple scattering. A theoretical analysis and experimental investigation reveals that in OCT, despite multiple scattering, the field backscattered from the sample is general ...

We present a functional imaging method based on triplet state kinetics. The triplet state of many known fluorophores shows a triplet lifetime typically in the order of ~10e-6 – 10e-3 s, 3-6 orders of magnitude longer than the associated fluorescence singlet lifetime. As a consequence triplet state sensing is more exposed to the microenvironment of fluorophores and can be used as a functional molecular antenna. By means of a modulated excitation scheme of pulses with varying duty cycles, the triplet state po

Optical microscopy has become a major non- or minimally invasive tool for investigating living organisms such as cells, tissues or small animals. Being such an essential tool for research and because lacking knowledge and insight in the working principles of tools often results in sub-optimal or outright wrong application, this books aims at teaching students in life sciences and biology the basic concepts for understanding their optical microscopes. In a first part, this manuscript starts by introducing ra

A two-dimensional (2-D) array (4 by 8) of single-photon avalanche diodes integrated in an industrial complementary metal-oxide-semiconductor (CMOS) process is presented. Each pixel combines a photodiode biased above its breakdown voltage in the so-called Geiger mode, a quenching resistor, and a simple comparator. The pitch between the pixels is 75 mum and the diameter of each pixel is 6.4 mum. The full integration allows reducing the number of charge carriers in a Geiger pulse. The electroluminescence respo

We present a functional imaging method based on triplet state kinetics. The triplet state of many known fluorophores show a triplet lifetime typically in the order of ~10e-6 – 10e-3 s, 3-6 orders of magnitude longer than the associated fluorescence singlet lifetime. As a consequence triplet state sensing is more exposed to the microenvironment of fluorophores and can be used as a functional molecular antenna. Using an adaptive modulated excitation scheme, these long living triplet state dynamics are accessi

By switching fluorophores on and off in either a deterministic or a stochastic manner, superresolution microscopy has enabled the imaging of biological structures at resolutions well beyond the diffraction limit. Superresolution optical fluctuation imaging (SOFI) provides an elegant way of overcoming the diffraction limit in all three spatial dimensions by computing higher-order cumulants of image sequences of blinking fluorophores acquired with a conventional widefield microscope. So far, three-dimensional

We report results on two-photon total-internal-reflection fluorescence correlation spectroscopy with radially polarized light. The combination of liquid crystal spatial light modulator, providing radial polarization, with ultrafast laser (picosecond Nd:GdV ...

Optical Coherence Tomography (OCT) is an imaging technique with high axial resolution in the micro-meter-scale range combined with a high sensitivity allowing for example to probe weakly back-scattering structures beneath the surface of biological tissues ...

The identification of a beta-cell tracer is a major quest in diabetes research. However, since MRI, PET and SPECT cannot resolve individual islets, optical techniques are required to assess the specificity of these tracers. We propose to combine Optical Co ...

Odorant receptors are an excellent example of natural superiority in specifically binding specific, small and hydrophobic molecules. They are of particular interest in the development of a sensor platform for G protein- coupled receptors (GPCRs). Odorant receptors (OR5) of Rattus norvegicus were incorporated into model membranes by in vitro synthesis and vectorial incorporation for achieving natural receptor function. The vectorial insertion of OR5 into the planar membrane and their lateral distribution, th

Optical coherence correlation spectroscopy (OCCS) allows studying kinetic processes at the single particle level using the backscattered light of nanoparticles. We extend the possibilities of this technique by increasing its signal-to-noise ratio by a fact ...

In this work we present a model for image formation in optical coherence microscopy. In the spectral domain detection, each wavenumber has a specific coherent transfer function that samples a different part of the object's spatial frequency spectrum. The r ...

Theo Lasser

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Total internal reflection fluorescence correlation spectroscopy (TIR-FCS) with low background and high count-rate per molecule

Towards in vivo small animal imaging

Massively parallel data processing for quantitative total flow imaging with optical coherence microscopy and tomography

Steerable filters for orientation estimation and localization of fluorescent dipoles

Detection efficiency in total internal reflection fluorescence microscopy

Image formation in fluorescence coherence-gated imaging through scattering media

High-speed laser Doppler imaging of blood flow in biological tissue

Dark-field optical coherence microscopy

Multiple scattering in optical coherence tomography. I. Investigation and modeling

Triplet State Imaging

Optical microscopy for biology and life sciences

First fully integrated 2-D array of single-photon detectors in standard CMOS technology

Triplet Imaging by Modulated Excitation

Multiplane 3D superresolution optical fluctuation imaging

High volume confinement in two-photon total-internal- reflection fluorescence correlation spectroscopy

Phase sensitive Fourier domain optical coherence tomography

Combined Optical Coherence and Fluorescence Microscopy to assess dynamics and specificity of pancreatic beta-cell tracers

Imaging of G protein-coupled receptors in solid- supported planar membranes at the single molecule level

Visible light optical coherence correlation spectroscopy

Image formation and tomogram reconstruction in optical coherence microscopy