KEYWORDS: Signal to noise ratio, Light sources and illumination, Fluorescence, Two photon imaging, In vivo imaging, Neurophotonics, Sensors, Neurons, Biological imaging, Brain
SignificanceGenetically encoded voltage indicators (GEVIs) are a valuable tool for studying neural circuits in vivo, but the relative merits and limitations of one-photon (1P) versus two-photon (2P) voltage imaging are not well characterized.AimWe consider the optical and biophysical constraints particular to 1P and 2P voltage imaging and compare the imaging properties of commonly used GEVIs under 1P and 2P excitation.ApproachWe measure the brightness and voltage sensitivity of voltage indicators from commonly used classes under 1P and 2P illumination. We also measure the decrease in fluorescence as a function of depth in the mouse brain. We develop a simple model of the number of measurable cells as a function of reporter properties, imaging parameters, and desired signal-to-noise ratio (SNR). We then discuss how the performance of voltage imaging would be affected by sensor improvements and by recently introduced advanced imaging modalities.ResultsCompared with 1P excitation, 2P excitation requires ∼104-fold more illumination power per cell to produce similar photon count rates. For voltage imaging with JEDI-2P in the mouse cortex with a target SNR of 10 (spike height to baseline shot noise), a measurement bandwidth of 1 kHz, a thermally limited laser power of 200 mW, and an imaging depth of >300 μm, 2P voltage imaging using an 80-MHz source can record from no more than ∼12 neurons simultaneously.ConclusionsDue to the stringent photon-count requirements of voltage imaging and the modest voltage sensitivity of existing reporters, 2P voltage imaging in vivo faces a stringent tradeoff between shot noise and tissue photodamage. 2P imaging of hundreds of neurons with high SNR at a depth of >300 μm will require either major improvements in 2P GEVIs or qualitatively new approaches to imaging.
S. Rolston, J. R. Anderson, U. Chukwu, J. Grover, J. Hertzberg, J. Hoffman, P. Kordell, J. Lee, C. Lobb, L. Orozco, S. Ravets, P. Solano, K. Voigt, F. Wellstood, J. Wong-Campos, G. Beadie, F. Fatemi
Hybrid quantum systems can be formed that combine the strengths of multiple platforms while avoiding the weaknesses. Here we report on progress toward a hybrid quantum system of neutral atom spins coupled to superconducting qubits. We trap laser-cooled rubidium atoms in the evanescent field of an ultrathin optical fiber, which will be suspended a few microns above a superconducting circuit that resonates at the hyperfine frequency of the Rb atoms, allowing magnetic coupling between the atoms and superconductor. As this will be done in a dilution refrigerator environment, the technical demands on the optical fiber is severe. We have developed and optimized a tapered fiber fabrication system, achieving optical transmission in excess of 99.95% , and fibers that can sustain 400 mW of optical power in a UHV environment. We have also optimized tapered fibers that can support higher order optical modes with high transmission (> 97%), which may be useful for different optical potential geometries. We have developed an in-situ tunable high-Q superconducting microwave resonator that can be tuned to within the resonator linewidth of the 6.8 GHz frequency of the Rb hyperfine transition.
The generation of intra-cavity superpositions of Bessel-Gauss beams in an axicon resonator is studied numerically
by means of a genetic algorithm. The coherent superposition of low order modes is induced by introducing crossed
wires within the simulated cavity. Two different strategies are shown to be equivalent for the generation of the
same superposition of two Bessel-Gauss beams with opposite azimuthal orders. In the first strategy the angle
between a pair of cross-wires is varied for mode selection, the second consists on introducing a number of crosswires
at equally spaced angles in which the number of wires corresponds exactly to the order of the superposed
modes. Our results suggest a direct method for generating experimentally a coherent mode superposition of
Bessel-Gauss beams using an axicon-based Bessel-Gauss resonator. These beams are relevant in areas such as
optical trapping and micromanipulatio
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.