The role of the interactive Kerr effect in two-photon optical multistability

1982 ◽  
Vol 45 (3) ◽  
pp. 255-258
Author(s):  
J. A. Hermann ◽  
J. N. Elgin ◽  
P. L. Knight
Keyword(s):  
Kerr Effect ◽  
Two Photon ◽  
Optical Multistability

Sensory Transmission is Bi-directionally Modulated by Astrocytic Ca2+ in Barrel Cortex of Behaving Mice

2021 ◽  
Author(s):  
Simeng Gu ◽  
Wei Wang ◽  
Kuan Zhang ◽  
Rou Feng ◽  
Naling Li ◽  
...  
Keyword(s):  
Sensory Input ◽  
Barrel Cortex ◽  
Synaptic Function ◽  
Metabolic Clearance ◽  
Sleep State ◽  
Two Photon Microscopy ◽  
Two Photon ◽  
Sensory Transmission

Abstract Different effects of astrocyte during sleep and awake have been extensively studied, especially for metabolic clearance by the glymphatic system, which works during sleep and stops working during waking states. However, how astrocytes contribute to modulation of sensory transmission during sleep and awake animals remain largely unknown. Recent advances in genetically encoded Ca2+ indicators have provided a wealth of information on astrocytic Ca2+, especially in their fine perisynaptic processes, where astrocytic Ca2+ most likely affects the synaptic function. Here we use two-photon microscopy to image astrocytic Ca2+ signaling in freely moving mice trained to run on a wheel in combination with in vivo whole-cell recordings to evaluate the role of astrocytic Ca2+ signaling in different behavior states. We found that there are two kinds of astrocytic Ca2+ signaling: a small long-lasting Ca2+ increase during sleep state and a sharp widespread but short-long-lasting Ca2+ spike when the animal was awake (fluorescence increases were 23.2 ± 14.4% for whisker stimulation at sleep state, compared with 73.3 ± 11.7% for at awake state, paired t-test, p < 0.01). The small Ca2+ transients decreased extracellular K+, hyperpolarized the neurons, and suppressed sensory transmission; while the large Ca2+ wave enhanced sensory input, contributing to reliable sensory transmission in aroused states. Locus coeruleus activation works as a switch between these two kinds of astrocytic Ca2+ elevation. Thus, we show that cortical astrocytes play an important role in processing of sensory input. These two types of events appear to have different pharmacological sources and may play a different role in facilitating the efficacy of sensory transmission.

scholarly journals Seizures start as silent microseizures by neuronal ensembles

2018 ◽  
Author(s):  
Michael Wenzel ◽  
Jordan P. Hamm ◽  
Darcy S. Peterka ◽  
Rafael MD Yuste
Keyword(s):  
Calcium Imaging ◽  
Travelling Wave ◽  
Inhibitory Neurons ◽  
Neural Activation ◽  
Calcium Dynamics ◽  
Neuronal Ensembles ◽  
Two Photon ◽  
Step Model

AbstractUnderstanding seizure formation and spread remains a critical goal of epilepsy research. While many studies have documented seizure spread, it remains mysterious how they start. We used fast in-vivo two-photon calcium imaging to reconstruct, at cellular resolution, the dynamics of focal cortical seizures as they emerge in epileptic foci (intrafocal), and subsequently propagate (extrafocal). We find that seizures start as intrafocal coactivation of small numbers of neurons (ensembles), which are electrographically silent. These silent “microseizures” expand saltatorily until they break into neighboring cortex, where they progress smoothly and first become detectable by LFP. Surprisingly, we find spatially heterogeneous calcium dynamics of local PV interneuron sub-populations, which rules out a simple role of inhibitory neurons during seizures. We propose a two-step model for the circuit mechanisms of focal seizures, where neuronal ensembles first generate a silent microseizure, followed by widespread neural activation in a travelling wave, which is then detected electrophysiologically.

scholarly journals A Study of the Magneto?Kerr and Other Effects at a Plasma Surface

1967 ◽  
Vol 20 (1) ◽  
pp. 29 ◽  
Author(s):  
LC Robinson
Keyword(s):  
Momentum Transfer ◽  
Kerr Effect ◽  
Collision Frequency ◽  
Absolute Measurement ◽  
High Electron ◽  
Surface Phenomena ◽  
Density Region ◽  
Plasma Surface ◽  
Microwave Reflection

The role of microwave reflection observations and particularly the magneto. microwave Kerr effect in the study of plasma surface phenomena is discussed. The method makes possible the absolute measurement of high electron surface densities in a density region not readily accessible to other experimental techniques, and it gives an indication of the collision frequency for momentum transfer.

OPTICAL LIMITING STUDIES IN PHOTOREFRACTIVE PURE AND IRON-DOPED Bi12SiO20 CRYSTALS

2000 ◽  
Vol 09 (02) ◽  
pp. 217-225 ◽  
Author(s):  
P. SREERAMANA AITHAL ◽  
P. PREM KIRAN ◽  
D. NARAYANA RAO
Keyword(s):  
Excited State Absorption ◽  
Optical Limiting ◽  
Photon Absorption ◽  
Limiting Behavior ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Iron Incorporation ◽  
Optical Limiter ◽  
Level Model

Optical limiting characteristics of pure and 150 ppm Fe-doped Bi 12 SiO 20 (BSO:Fe) crystals are studied at high intensity nanosecond pulse regime. When the input light is at 532 nm and at 595 nm with 6 ns pulse duration, a good optical limiting behavior is observed due to simultaneous effect of trap assisted excited state absorption and two photon absorption. The precise role of the internal defects due to impurity centers present in the crystal lattice is explained on the basis of a four level model. This study reveal that the increased nonlinear absorption due to iron incorporation in BSO makes it an excellent passive optical limiter.

scholarly journals Non-Markovian features in semiconductor quantum optics: quantifying the role of phonons in experiment and theory

Nanophotonics ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 655-683 ◽  
Author(s):  
Alexander Carmele ◽  
Stephan Reitzenstein
Keyword(s):  
Quantum Electrodynamics ◽  
Theoretical Models ◽  
Cavity Quantum Electrodynamics ◽  
Heisenberg Equation ◽  
Linear Absorption ◽  
Electron Phonon Interaction ◽  
Two Photon ◽  
Quantum State Preparation ◽  
Path Integral Method

AbstractWe discuss phonon-induced non-Markovian and Markovian features in QD-based quantum nanooptics. We cover lineshapes in linear absorption experiments, phonon-induced incoherence in the Heitler regime, and memory correlations in two-photon coherences. To qualitatively and quantitatively understand the underlying physics, we present several theoretical models that capture the non-Markovian properties of the electron–phonon interaction accurately in different regimes. Examples are the Heisenberg equation of motion approach, the polaron master equation, and Liouville propagator techniques in the independent boson limit and beyond via the path integral method. Phenomenological modeling overestimates typically the dephasing due to the finite memory kernel of phonons and we give instructive examples of phonon-mediated coherence such as phonon-dressed anticrossings in Mollow physics, robust quantum state preparation, cavity feeding, and the stabilization of the collapse and revival phenomenon in the strong coupling limit of cavity quantum electrodynamics.

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