We present progress towards demonstrating multi-passed stimulated Raman scattering microscopy and multi-passed transmission electron microscopy. A multi-pass microscope interrogates a sample multiple times in a cyclical and deterministic fashion. This can lead to a metrological advantage for imaging weak scatterers. The enhanced sensitivity can yield a significant reduction in damage imparted to biological samples or can reduce image acquisition time. The approach compares favorably with imaging techniques using squeezed or entangled probe states, but avoids the technical complexity associated with the production of such states.
This talk will describe label-free microscopy protocols which optimize the (quantum) information acquired from the imaging interaction between the probing optical field and the imaged sample. These protocols are useful in high throughput or low dose applications, where image formation benefits from efficient use of each probing photon. We illustrate these methods with proof-of-concept demonstrations of flow cytometry, multi-photon Raman imaging and fluorescence lifetime imaging.
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: Laser systems engineering, Beam splitters, Phase shifts, Interferometers, Chemical species, Laser optics, Phase measurement, High power lasers, Electromagnetism
Light-pulse atom interferometers are excellent probes for studying gravitational interactions in quantum systems. The characteristics of the atom optics lasers are often essential in determining the performance of an atom interferometer. Here we have built a high-power laser system that enables Stark-shift-compensated dual beam splitters. Technical details of the laser system will be discussed. The second part will focus on the observation of a gravitational Aharonov-Bohm effect. When operating the interferometer with a source mass in a nonlocal regime, we identify the non-zero action-induced phase shift, deviating from that induced by deflections, as the gravitational Aharonov-Bohm phase shift.
We present an analysis of the robustness of existing analytic schemes for the implementation of an atomic fountain interferometer, and develop concepts for improving this robustness through the use of optimal control theory. For an interferometer operating in the Raman regime, we consider an implementation that manipulates the atomic momentum states with a series of Rabi pulses, and analyze how robust the population dynamics are with respect to variations in the effective pulse amplitude seen by the atoms in the atomic clouds, and variations in the initial velocity of the atoms relative to the rest frame. We then show that using rapid adiabatic passage to implement momentum transfer can significantly improve this robustness. Finally, we formulate the most general control conditions for an atomic fountain interferometer and design a functional that can be used for an ensemble optimization over the robustness landscape. We show preliminary results of optimizing the system using Krotov's method, suggesting that optimal control may be able to significantly enhance the robustness of atom interferometers.
We use a dual-species atom interferometer with 2 s of free-fall time to measure the relative acceleration between 85Rb and 87Rb wave packets in the Earth's gravitational field. Systematic errors arising from kinematic differences between the isotopes are suppressed by calibrating the angles and frequencies of the interferometry beams. We find an Eötvös parameter of [1.6 +/- 1.8 (stat) +/- 3.4 (syst)] x 10^-12, consistent with zero violation of the equivalence principle. With a resolution of up to 1.4 x 10^-11 g per shot, we demonstrate the highest sensitivity to the Eötvös parameter of any laboratory experiment.
We report improvements to our atom-interferometer based Sagnac gyroscope which uses stimulated Raman transitions to manipulate atomic wavepackets of cesium atoms. Using counter-propagating high-flux atomic beams, we form two interferometers with opposite Sagnac phase shifts that share key components such as Raman atomic state manipulation beams. Subtracting the two interferometer signals allows the common-mode rejection of spurious noise sources and various systematic effects. Preliminary results indicate a short term sensitivity of 3 X 10-9 (rad/s) (root) Hz.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.