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{1555} | |||||
Recently I've been underwhelmed by the performance of adaptive optics (AO) for imaging head-fixed cranial-window mice. There hasn't been much of an improvement, despite significant optimization effort. This begs the question: where are AO microscopes used? When the purpose of a paper is to explain and qualify an novel AO approach, the improvement is always good, >> 2x. Yet, in the one paper (first below) when the purpose was neuroscience, not optics, the results are less inspiring. Are the results from the optics papers cherry-picked? Thalamus provides layer 4 of primary visual cortex with orientation- and direction-tuned inputs Wenzhi Sun, Zhongchao Tan, Brett D Mensh & Na Ji 2016 https://www.nature.com/articles/nn.4196
Direct wavefront sensing for high-resolution in vivo imaging in scattering tissue Kai Wang, Wenzhi Sun, Christopher T. Richie, Brandon K. Harvey, Eric Betzig & Na Ji, 2015 https://www.nature.com/articles/ncomms8276
Multiplexed aberration measurement for deep tissue imaging in vivo Chen Wang, Rui Liu, Daniel E Milkie, Wenzhi Sun, Zhongchao Tan, Aaron Kerlin, Tsai-Wen Chen, Douglas S Kim & Na Ji 2014 https://www.nature.com/articles/nmeth.3068
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{1490} | |||||
PMID-21527931 Two-photon absorption properties of fluorescent proteins
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{1417} |
ref: -0
tags: synaptic plasticity 2-photon imaging inhibition excitation spines dendrites synapses 2p
date: 08-14-2020 01:35 gmt
revision:3
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PMID-22542188 Clustered dynamics of inhibitory synapses and dendritic spines in the adult neocortex.
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{1478} |
ref: -2013
tags: 2p two photon STED super resolution microscope synapse synaptic plasticity
date: 08-14-2020 01:34 gmt
revision:3
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PMID-23442956 Two-Photon Excitation STED Microscopy in Two Colors in Acute Brain Slices
PMID-29932052 Chronic 2P-STED imaging reveals high turnover of spines in the hippocampus in vivo | |||||
{1435} | |||||
PMID-18204458 High-speed, low-photodamage nonlinear imaging using passive pulse splitters
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{1499} | |||||
PMID-24877017 Optimal lens design and use in laser-scanning microscopy
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{1486} |
ref: -2019
tags: non degenerate two photon excitation fluorophores fluorescence OPO optical parametric oscillator
date: 10-31-2019 20:53 gmt
revision:0
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Efficient non-degenerate two-photon excitation for fluorescence microscopy | |||||
{1479} | |||||
Can we image biological tissue with entangled photons? How much fluorescence can we expect, based on reasonable concentrations & published ETPA cross sections? Start with beer's law: = absorbance; = sample length, 10 μm, 1e-3 cm; = concentration, 10 μmol; = cross-section, for ETPA assume (this is based on a FMN based fluorophore; actual cross-section may be higher). Including Avogadro's number and , Now, add in quantum efficiency (Rhodamine); collection efficiency ; and an incoming photon pair flux of (which roughly about the limit for quantum behavior; n = 0.1 photons / mode; will add this calculation). This is very low, but within practical imaging limits. As a comparison, incoherent 2p imaging creates ~ 100 photons per pulse, of which 10 make it to the detector; for 512 x 512 pixels at 15fps, the dwell time on each pixel is 20 pulses of a 80 MHz Ti:Sapphire laser, or ~ 200 photons. Note the pair flux is per optical mode; for a typical application, we'll use a Nikon 16x objective with a 600 μm Ø FOV and 0.8 NA. At 800 nm imaging wavelength, the diffraction limit is 0.5 μm. This equates to about addressable modes in the FOV. Then an illumination of photons / sec / mode equates to photons over the whole field; if each photon pair has an energy of , this is equivalent to 300 mW. 100mW is a reasonable limit, hence scale incoming flux to pairs /sec. Hence, the imaging mode is power limited, and not quantum limited (if you could get such a bright entangled source). And right now that's the limit -- for a BBO crystal, circa 1998 experimenters were getting 1e4 photons / sec / mW. So, pairs / sec would require 23 GW. Yikes. More efficient entangled sources have been developed, using periodically-poled potassium titanyl phosphate (PPPTP), which (again assuming linearity) puts the power requirement at 23 MW. This is within the reason of q-switched lasers, but still incredibly inefficient. The down-conversion process is not linear in intensity, which is why Goodson pumps with SHG from a Ti:sapphire to yield ~1e7 photons; but this of induces temporal correlations which increase the frequency of incoherent TPA. Still, combining PPPTP with a Ti:sapphire laser could result in 1e13 photons / sec, which is sufficient for scanned microscopy. Since the laser is pulsed, it will still be subject to incoherent TPA; but that's OK, the point is to reduce the power going into the animal via larger ETPA cross-section. The answer to above is a tentative yes. Upon the development of brighter entangled sources (e.g. arrays of quantum structures), this can move to fully widefield imaging. | |||||
{1474} | |||||
Various papers put out by the Goodson group:
And from a separate group at Northwestern:
Regarding high fluence sources, quantum dots / quantum structures seem promising. | |||||
{1475} |
ref: -2017
tags: two photon holographic imaging Arch optogenetics GCaMP6
date: 09-12-2019 19:24 gmt
revision:1
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PMID-28053310 Simultaneous high-speed imaging and optogenetic inhibition in the intact mouse brain.
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{1467} |
ref: -2017
tags: neuromorphic optical computing nanophotonics
date: 06-17-2019 14:46 gmt
revision:5
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Progress in neuromorphic photonics
See also :
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{1418} |
ref: -0
tags: nanophotonics interferometry neural network mach zehnder interferometer optics
date: 06-13-2019 21:55 gmt
revision:3
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Deep Learning with Coherent Nanophotonic Circuits
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PMID-29089483 Three-dimensional scanless holographic optogenetics with temporal focusing (3D-SHOT).
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PMID-30635577 Functional imaging of visual cortical layers and subplate in awake mice with optimized three photon microscopy
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PMID-22308458 Optically monitoring voltage in neurons by photo-induced electron transfer through molecular wires.
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PMID-21880826[0] http://cshprotocols.cshlp.org/content/2011/9/pdb.prot065474.full?rss=1
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