An official website of the United States government
We present a quantum optics-based detection method for determining the position and current of an electron beam. As electrons pass through a dilute vapor of rubidium atoms, their magnetic field perturbs the atomic spin's quantum state and causes polarization rotation of a laser resonant with an optical transition of the atoms. By measuring the polarization rotation angle across the laser beam, we recreate a 2D projection of the magnetic field and use it to determine the e-beam position, size, and total current. We tested this method for an e-beam with currents ranging from 30 to 110 μA. Our approach is insensitive to electron kinetic energy, and we confirmed that experimentally between 10 and 20 keV. This technique offers a unique platform for noninvasive characterization of charged particle beams used in accelerators for particle and nuclear physics research.
more »
« less
Direct calibration of laser intensity via Ramsey interferometry for cold atom imaging
A majority of ultracold atom experiments utilize resonant absorption imaging techniques to obtain the atomic density. To make well-controlled quantitative measurements, the optical intensity of the probe beam must be precisely calibrated in units of the atomic saturation intensity I sat . In quantum gas experiments, the atomic sample is enclosed in an ultra-high vacuum system that introduces loss and limits optical access; this precludes a direct determination of the intensity. Here, we use quantum coherence to create a robust technique for measuring the probe beam intensity in units of I sat via Ramsey interferometry. Our technique characterizes the ac Stark shift of the atomic levels due to an off-resonant probe beam. Furthermore, this technique gives access to the spatial variation of the probe intensity at the location of the atomic cloud. By directly measuring the probe intensity just before the imaging sensor our method in addition yields a direct calibration of imaging system losses as well as the quantum efficiency of the sensor.
more »
« less
- Award ID(s):
- 2120757
- PAR ID:
- 10424697
- Date Published:
- Journal Name:
- Optics Express
- Volume:
- 31
- Issue:
- 11
- ISSN:
- 1094-4087
- Page Range / eLocation ID:
- 17893
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Ultracold atoms are an ideal platform for understanding system-reservoir dynamics of many-body systems. Here, we study quantum back-action in atomic Bose-Einstein condensates, weakly interacting with a far-from resonant, i.e., dispersively interacting, probe laser beam. The light scattered by the atoms can be considered as a part of quantum measurement process, whereby the change in the system state derives from measurement back-action. We experimentally quantify the resulting back-action in terms of the deposited energy. We model the interaction of the system and environment with a generalized measurement process, leading to a Markovian reservoir. Further, we identify two systematic sources of heating and loss: a stray optical lattice and probe-induced light-assisted collisions (an intrinsic atomic process). The observed heating and loss rates are larger for blue detuning than for red detuning, where they are oscillatory functions of detuning with increased loss at molecular resonances and reduced loss between molecular resonances.more » « less
-
An interferometric pump-probe microscope with two counterpropagating probe beams is developed and characterized. Application of the technique to a porphyrin derivative thin film shows that the technique is sensitive to variations in local film morphology that are undetectable with conventional pump-probe techniques. Analysis of the material response shows that the technique enhances signal levels measuring transient changes in the optical constants, limited by the asymmetry of the probe beam beamsplitter. The technique also provides the ability to distinguish contributions to the overall pump-probe response from changes to the real and imaginary components of the optical constants.more » « less
-
In this paper, we have used the angular spectrum propagation method and numerical simulations of a single random phase encoding (SRPE) based lensless imaging system, with the goal of quantifying the spatial resolution of the system and assessing its dependence on the physical parameters of the system. Our compact SRPE imaging system consists of a laser diode that illuminates a sample placed on a microscope glass slide, a diffuser that spatially modulates the optical field transmitting through the input object, and an image sensor that captures the intensity of the modulated field. We have considered two-point source apertures as the input object and analyzed the propagated optical field captured by the image sensor. The captured output intensity patterns acquired at each lateral separation between the input point sources were analyzed using a correlation between the captured output pattern for the overlapping point-sources, and the captured output intensity for the separated point sources. The lateral resolution of the system was calculated by finding the lateral separation values of the point sources for which the correlation falls below a threshold value of 35% which is a value chosen in accordance with the Abbe diffraction limit of an equivalent lens-based system. A direct comparison between the SRPE lensless imaging system and an equivalent lens-based imaging system with similar system parameters shows that despite being lensless, the performance of the SRPE system does not suffer as compared to lens-based imaging systems in terms of lateral resolution. We have also investigated how this resolution is affected as the parameters of the lensless imaging system are varied. The results show that SRPE lensless imaging system shows robustness to object to diffuser-to-sensor distance, pixel size of the image sensor, and the number of pixels of the image sensor. To the best of our knowledge, this is the first work to investigate a lensless imaging system’s lateral resolution, robustness to multiple physical parameters of the system, and comparison to lens-based imaging systems.more » « less
-
The ability to probe and control matter at the picometer scale is essential for advancing quantum and energy technologies. Scanning transmission electron microscopy offers powerful capabilities for materials analysis and modification, but sample damage, drift, and scan distortions hinder single atom analysis and deterministic manipulation. Materials analysis and modification via electron–solid interactions can be transformed by precise delivery of electrons to a specified atomic location, maintaining the beam position despite drift, and minimizing collateral dose. Here a fast, low‐dose, sub‐20‐pm precision electron beam positioning technique is developed, “atomic lock‐on,” (ALO), which offers the ability to position the beam on a specific atomic columnwithoutpreviously irradiating that column. This technique is used to lock onto a single selected atomic location to repeatedly measure its weak electron energy loss signal despite sample drift. Moreover, electron beam‐matter interactions in single atomic events are measured with time resolution. This enables observation of single‐atom dynamics, such as atomic bistability, revealing partially bonded atomic configurations and recapture phenomena. This opens prospects for using electron microscopy for high‐precision measurements and deterministic control of matter for quantum technologies.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1364/OE.488710
