KEYWORDS: Transmission electron microscopy, Prisms, Pulsed laser operation, Monochromators, Microscopy, Magnetism, Laser energy, Electron microscopy, Electron microscopes, Control systems
Multi-pass optical and electron microscopes outperform standard single-pass instruments in dose-limited regimes and have been shown to be quantum optimal. We report on recent progress towards demonstrating multi-pass transmission electron microscopy with a focus on the electron gun and monochromator system. Prompt electron emission from a Schottky emitter is laser-triggered with nanosecond optical pulses, and a single-photon emission process can be used to generate high current pulses with narrow intrinsic energy spreads. These pulse properties could be useful for nanosecond time-resolved and potentially single-shot microscopy experiments and are well-suited for use in a multi-pass transmission electron microscope.
KEYWORDS: Microscopy, Sensors, Signal to noise ratio, Image enhancement, Point spread functions, Confocal microscopy, Diffraction, Image resolution, Super resolution, Single photon
Technological advancements in the creation, manipulation and detection of quantum states of light have motivated the application of such states to overcome classical limits in sensing and imaging. In particular, there has been a surge of recent interest in super-resolution imaging based on principles of quantum optics. However, the application of such schemes for practical imaging of biological samples is demanding in terms of signal-to-noise ratio, speed of acquisition and robustness with respect to sample labeling. Here, we re-introduce the concept of quantum image scanning microscopy (Q-ISM), a super-resolution method that enhances the classical image scanning microscopy (ISM) method by measuring photon correlations. Q-ISM was already utilized to achieve super-resolved images of a biological sample labeled with fluorescent nanoscrystals whose contrast is based entirely on a quantum optical phenomenon, photon antibunching. We present here an experimental demonstration of the method and discuss with further details its prospects for application in life science microscopy.
Far-field optical microscopy beyond the Abbe diffraction limit, making use of nonlinear excitation (e.g. STED), or temporal fluctuations in fluorescence (PALM, STORM, SOFI) is already a reality. In contrast, overcoming the diffraction limit using non-classical properties of light is very difficult to achieve due to the fragility of quantum states of light. Here, we experimentally demonstrate superresolution microscopy based on quantum properties of light naturally emitted by fluorophores used as markers in fluorescence microscopy. Our approach is based on photon antibunching, the tendency of fluorophores to emit photons one by one rather than in bursts. Although a distinctively quantum phenomenon, antibunching is readily observed in most common fluorophores even at room temperature.
This nonclassical resource can be utilized directly to enhance the imaging resolution, since the non-classical far-field intensity correlations induced by antibunching carry high spatial frequency information on the spatial distribution of emitters. Detecting photon statistics simultaneously in the entire field of view, we were able to detect non-classical correlations of the second and third order, and reconstructed images with resolution significantly beyond the diffraction limit.
Alternatively, we demonstrate the utilization of antibunching for augmenting the capabilities of localization-based superresolution imaging in the presence of multiple emitters, using a novel detector comprised of an array of single photon detectors connected to a densely packed fiber bundle. These features allow us to enhance the spatial and temporal resolution with which multiple emitters can be imaged compared with other techniques that rely on CCD cameras.
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