Schroedinger cat-like states by conditional measurements on a beam-splitter

A scheme for generating Schr\"{o}dinger cat-like states of a single-mode optical field by means of conditional measurement is proposed. Feeding into a beam splitter a squeezed vacuum and counting the photons in one of the output channels, the conditional states in the other output channel exhibit a number of properties that are very similar to those of superpositions of two coherent states with opposite phases. We present analytical and numerical results for the photon-number and quadrature-component distributions of the conditional states and their Wigner and Husimi functions. Further, we discuss the effect of realistic photocounting on the states.Comment: 6 figures(divided in subfigures) using a4.st

Optical sectioning in wide-field microscopy obtained by dynamic structured light illumination and detection based on a smart pixel detector array

Optical sectioning in wide-field microscopy is achieved by illumination of the object with a continuously moving single-spatial-frequency pattern and detecting the image with a smart pixel detector array. This detector performs an on-chip electronic signal processing that extracts the optically sectioned image. The optically sectioned image is directly observed in real time without any additional postprocessing. (C) 2003 Optical Society of America

High light field confinement for Fluorescence Correlation Spectroscopy using a Solid Immersion Lens

In this paper we present recent single molecule detection experiment using a solid immersion lens (SIL) for fluorescent correlation spectroscopy measurements. We compared the performance of the SIL in combination with an air objective (40×, numerical aperture (NA)=0.6) with a water immersion objective (40×, NA=1.15) in a confocal microscope system (ConfoCorr 1). Important parameters for single molecule experiments such as collection efficiency and excitation field confinement were investigated. Although the two set-ups have similar numerical aperture the measurements demonstrated higher field confinement and better collection efficiency for the SIL system in comparison to the conventional confocal set-up. Adding spherical aberrations shifts the sample volume up to 4 μm away from the plane surface of the SIL and conserves a diffraction limited focal volume. In this case the FCS autocorrelation demonstrates a free 3D diffusion of dye molecules in a highly confined light field

Parallel single molecule detection with a fully integrated single-photon 2X2 CMOS detector array

We present parallel single molecule detection (SMD) and fluorescence correlation spectroscopy (FCS) experiments with a fully integrated complementary metal oxide semiconductor (CMOS) single-photon 2 X 2 detector array. Multifocal excitation is achieved with a diffractive optical element (DOE). Special emphasis is placed on parallelization of the total system. The performance of the novel single-photon CMOS detector is investigated and compared to a state-of-the-art single-photon detecting module [having an actively quenched avalanche photodiode (APD)] by measurements on free diffusing molecules at different concentrations. Despite the order of magnitude lower detection efficiency of the CMOS detector compared to the state-of-the-art single-photon detecting module, we achieve single molecule sensitivity and reliably determine molecule concentrations. In addition, the CMOS detector performance for the determination of the fraction of slowly diffusing molecules in a primer solution (two-component analysis) is demonstrated. The potential of this new technique for high-throughput confocal-detection-based systems is discussed. (C) 2004 Society of Photo-Optical Instrumentation Engineers

Fluorescence lifetime images and correlation spectra obtained by multidimensional TCSPC

Multi-dimensional time-correlated single photon counting (TCSPC) is based on the excitation of the sample by a high-repetition rate laser and the detection of single photons of the fluorescence signal in several detection channels. Each photon is characterised by its time in the laser period, its detection channel number, and several additional variables such as the coordinates of an image area, or the time from the start of the experiment. Combined with a confocal or two-photon laser scanning microscope and a pulsed laser, multi-dimensional TCSPC makes a fluorescence lifetime technique with multi-wavelength capability, near-ideal counting efficiency, and the capability to resolve multi-exponential decay functions. We show that the same technique and the same hardware can be used to for precision fluorescence decay analysis, fluorescence correlation spectroscopy (FCS), and fluorescence intensity distribution analysis (FIDA and FILDA) in selected spots of a sample

Fluorescence lifetime images and correlation spectra obtained by multidimensional time-correlated single photon counting

Multidimensional time‐correlated single photon counting (TCSPC) is based on the excitation of the sample by a high‐repetition rate laser and the detection of single photons of the fluorescence signal in several detection channels. Each photon is characterized by its arrival time in the laser period, its detection channel number, and several additional variables such as the coordinates of an image area, or the time from the start of the experiment. Combined with a confocal or two‐photon laser scanning microscope and a pulsed laser, multidimensional TCSPC makes a fluorescence lifetime technique with multiwavelength capability, near‐ideal counting efficiency, and the capability to resolve multiexponential decay functions. We show that the same technique and the same hardware can be used for precision fluorescence decay analysis and fluorescence correlation spectroscopy (FCS) in selected spots of a sample