11 research outputs found
Imaging of Rydberg Impurities in an Ultracold Atomic Gas
This thesis investigates how a single highly excited atom, called Rydberg atom, can be optically imaged. Direct detection methods based on the scattering of light are hardly applicable due to the small scattering rate of the ground to Rydberg state transition. Instead, a cloud of ground state atoms, normally absorptive, is rendered transparent using electromagnetically induced transparency (EIT), involving an auxiliary probe Rydberg state. The cloud acts as a contrast medium, whose optical response is locally perturbed by the strong Rydberg-Rydberg interaction between the probe and the Rydberg impurity which we want to detect. This perturbation restores absorption within a small volume around the impurity, readily detected and
spatially resolved on a camera. We call this technique Interaction Enhanced Imaging (IEI). To implement IEI we characterize the optical response of the EIT contrast
medium in absence of interactions. By combining measurements of the spatially resolved optical spectrum and of the total Rydberg atom number, we can reconstruct
the full one-body density matrix of the three-level system. Next, we excite |nS> or |nP> states and, using IEI, we demonstrate spatially resolved imaging, enabling us
to study dipolar energy transport. To reach single impurity sensitivity we investigate our current detection fidelity and characterize the signal and noise contributions in
IEI. We model our interacting system, finding good agreement with experimental data. Based on this model, we predict combinations of Rydberg states for which single-shot single impurity sensitivity should be possible in future experiments
Flexible multi-beam light-sheet fluorescence microscope for live imaging without striping artifacts
The development of light-sheet fluorescence microscopy (LSFM) has greatly expanded the experimental capabilities in many biological and biomedical research fields, enabling for example live studies of murine and zebrafish neural activity or of cell growth and division. The key feature of the method is the selective illumination of a sample single plane, providing an intrinsic optical sectioning and allowing direct 2D image recording. On the other hand, this excitation scheme is more affected by absorption or scattering artifacts in comparison to point scanning methods, leading to un-even illumination. We present here an easily implementable method, based on acousto-optical deflectors (AOD), to overcome this obstacle. We report the advantages provided by flexible and fast AODs in generating simultaneous angled multiple beams from a single laser beam and in fast light sheet pivoting and we demonstrate the suppression of illumination artifacts
Effects of excitation light polarization on fluorescence emission in two-photon light-sheet microscopy
Light-sheet microscopy (LSM) is a powerful imaging technique that uses a
planar illumination oriented orthogonally to the detection axis. Two-photon
(2P) LSM is a variant of LSM that exploits the 2P absorption effect for sample
excitation. The light polarization state plays a significant, and often
overlooked, role in 2P absorption processes. The scope of this work is to test
whether using different polarization states for excitation light can affect the
detected signal levels in 2P LSM imaging of typical biological samples with a
spatially unordered dye population. Supported by a theoretical model, we
compared the fluorescence signals obtained using different polarization states
with various fluorophores (fluorescein, EGFP and GCaMP6s) and different samples
(liquid solution and fixed or living zebrafish larvae). In all conditions, in
agreement with our theoretical expectations, linear polarization oriented
parallel to the detection plane provided the largest signal levels, while
perpendicularly-oriented polarization gave low fluorescence signal with the
biological samples, but a large signal for the fluorescein solution. Finally,
circular polarization generally provided lower signal levels. These results
highlight the importance of controlling the light polarization state in 2P LSM
of biological samples. Furthermore, this characterization represents a useful
guide to choose the best light polarization state when maximization of signal
levels is needed, e.g. in high-speed 2P LSM.Comment: 16 pages, 4 figures. Version of the manuscript accepted for
publication on Biomedical Optics Expres
Dual-beam confocal light-sheet microscopy via flexible acousto-optic deflector
Confocal detection in digital scanned laser light-sheet fluorescence microscopy (DSLM) has been established as a gold standard method to improve image quality. The selective line detection of a complementary metal-oxide-semiconductor camera (CMOS) working in rolling shutter mode allows the rejection of out-of-focus and scattered light, thus reducing background signal during image formation. Most modern CMOS have two rolling shutters, but usually only a single illuminating beam is used, halving the maximum obtainable frame rate. We report on the capability to recover the full image acquisition rate via dual confocal DSLM by using an acousto-optic deflector. Such a simple solution enables us to independently generate, control and synchronize two beams with the two rolling slits on the camera. We show that the doubling of the imaging speed does not affect the confocal detection high contrast
Flexible Multi-Beam Light-Sheet Fluorescence Microscope for Live Imaging Without Striping Artifacts
The development of light-sheet fluorescence microscopy (LSFM) has greatly expanded the experimental capabilities in many biological and biomedical research fields, enabling for example live studies of murine and zebrafish neural activity or of cell growth and division. The key feature of the method is the selective illumination of a sample single plane, providing an intrinsic optical sectioning and allowing direct 2D image recording. On the other hand, this excitation scheme is more affected by absorption or scattering artifacts in comparison to point scanning methods, leading to un-even illumination. We present here an easily implementable method, based on acousto-optical deflectors (AOD), to overcome this obstacle. We report the advantages provided by flexible and fast AODs in generating simultaneous angled multiple beams from a single laser beam and in fast light sheet pivoting and we demonstrate the suppression of illumination artifacts
Realisation of relaxed static stability on a commercial transport
SIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
Fast multi-directional DSLM for confocal detection without striping artifacts
In recent years light-sheet fluorescence microscopy (LSFM) has become a cornerstone technology for neuroscience, improving the quality and capabilities of 3D imaging. By selectively illuminating a single plane, it provides intrinsic optical sectioning and fast image recording, while minimizing out of focus fluorescence background, sample photo-damage and photo-bleaching. However, images acquired with LSFM are often affected by light absorption or scattering effects, leading to un-even illumination and striping artifacts. In this work we present an optical solution to this problem, via fast multi-directional illumination of the sample, based on an acousto-optical deflector (AOD). We demonstrate that this pivoting system is compatible with confocal detection in digital scanned laser light-sheet fluorescence microscopy (DSLM) by using a pivoted elliptical-Gaussian beam. We tested its performance by acquiring signals emitted by specific fluorophores in several mouse brain areas, comparing the pivoting beam illumination and a traditional static one, measuring the point spread function response and quantifying the striping reduction. We observed real-time shadow suppression, while preserving the advantages of confocal detection for image contrast
Direct activation of zebrafish neurons by ultrasonic stimulation revealed by whole CNS calcium imaging
Objective: Ultrasounds (US) use in neural engineering is so far mainly limited to ablation through high intensity focused ultrasound (HIFU), but interesting preliminary results show that low frequency low intensity ultrasound (LILFU) could be instead used to modulate neural activity. However, the extent of this modulatory ability of US is still unclear, as in in vivo studies it is hard to disentangle the contribution to neural responses of direct activation of the neuron by US stimulation and indirect activation due either to sensory response to mechanical stimulation associated to US, or to propagation of activity from neighboring areas. Here, we aim at showing how to separate the three effects and assess the presence of direct response to US stimulation in zebrafish. Approach: We observed in zebrafish larvae brain-wide US-induced activity patterns through calcium imaging microscopy. Sensory response to mechanical stimulation was assessed with a US shield. Activity propagation was assessed with inter-area latency evaluation. Main results: We prove that in selected brain regions zebrafish neural response is mainly due to direct activation, later spreading to the other regions. Shielding the neurons from direct US stimulation resulted in a significantly attenuated response, showing that sensory stimulation does not play a prominent role. Significance: US non-invasive neuromodulatory approach might lead to novel ways to test and control neural activity, and hence to novel neuromodulatory therapies. Future studies will focus on the biophysical structure of directly responsive neurons to capture the mechanisms of US induced activity