Photon Echo Process
Photon Echo Process - Related Videos
01:06
Echo
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2023
The human ear cannot distinguish between two sources of sound if they happen to reach within a specific time interval, typically 0.1 seconds apart. More than this, and they are perceived as separate sources. Imagine the sound is reflected back to the ears. Assuming that the source is very close to the human, the difference between hearing the two sounds—the emitted sound and the reflected sound—may be more than the minimum time for perceiving distinct sounds. If this is the case, then the...
10:00
Gradient Echo Quantum Memory in Warm Atomic Vapor
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Cited by 2 •
2013
The gradient echo memory is a protocol for storing optical quantum states of light in atomic ensembles. Quantum memory is a key element of a quantum repeater, which can extend the range of quantum key distribution. We outline the operation of the scheme when implemented in a 3-level atomic ensemble.
04:28
Two-Photon Microscopy for Studying Microglial Process Attraction Toward a Compound in a Mouse Brain Slice
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2025
Source: Etienne, F. et al. Two-photon Imaging of Microglial Processes' Attraction Toward ATP or Serotonin in Acute Brain Slices. J. Vis. Exp. (2019)This video demonstrates the use of two-photon microscopy to study the attraction of microglial processes toward an injected compound in brain slices. It provides an overview of preparing mouse brain slices, injecting a chemoattractant test compound, and imaging fluorescently labeled microglia to visualize their responses.
16:31
Echo Particle Image Velocimetry
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Cited by 10 •
2012
An echo particle image velocimetry (EPIV) system capable of acquiring two-dimensional fields of velocity in optically opaque fluids or through optically opaque geometries is described, and validation measurements in pipe flow are reported.
08:11
Ultrasound Tissue Characterization of Human Achilles Tendon by Stability Quantification of Echo Patterns
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2025
Ultrasound is the approach most commonly adopted in the clinical setting for the assessment of the size and structure of the Achilles tendon. To expand the Achilles tendon assessment in a more comprehensive manner, the ultrasound tissue characterization (UTC) approach has recently been proposed and validated in clinical studies.
FAQs
Inhomogeneous broadening gives different emitters different optical evolution rates, so their phases spread after coherent excitation. The second pulse reverses this phase evolution rather than eliminating the underlying frequency differences. As the phase trajectories converge, the ensemble generates an echo. This makes the delayed signal a way to study how optical coherence survives within a nonuniform material.
The first pulse establishes coherent excitation, and the second pulse changes the subsequent phase evolution of the emitters. The echo appears after the ensemble has had time to rephase, so its delay is linked to the pulse sequence and the stored coherence. Adjusting the sequence therefore provides a controlled way to examine ultrafast optical dynamics and coherence storage.
Echo timing indicates how long coherence is retained before rephasing produces delayed emission. In engineering studies, this observation helps evaluate materials whose optical behavior must be controlled at ultrafast timescales. The measurement also connects microscopic phase evolution with photonic-device performance, allowing researchers to examine dephasing and coherence storage through an optical signal.
An experiment applies a first optical pulse to create coherent excitation, waits for phase evolution in the ensemble, and then applies a second pulse to reverse the effects of inhomogeneous broadening. Researchers monitor the resulting delayed light pulse and relate its timing to dephasing and coherence storage. This sequence provides an optical readout of the ensemble's evolving coherence.
The delayed emission preserves information about how optical coherence evolves across an ensemble with broadened responses. Because echo timing is connected to dephasing and coherence storage, measurements can characterize material behavior through the emitted signal. This makes the process useful for studying optical transitions and evaluating materials with the resolution needed for engineering applications.
Engineering researchers use photon echoes to evaluate optical materials and develop systems that manipulate light on ultrafast timescales. The same coherence-control principles support optical signal processing, quantum memories, and coherent communications. In these applications, the important outcome is controlled storage and rephasing of optical coherence, which links material properties to the operation of photonic devices.