Limits...
Single-shot tomographic movies of evolving light-velocity objects.

Li Z, Zgadzaj R, Wang X, Chang YY, Downer MC - Nat Commun (2014)

Bottom Line: Tomography--cross-sectional imaging based on measuring radiation transmitted through an object along different directions--enables non-invasive imaging of hidden stationary objects, such as internal bodily organs, from their sequentially measured projections.Here we adapt tomographic methods to visualize--in one laser shot--the instantaneous structure and evolution of a laser-induced object propagating through a transparent Kerr medium.Our technique could potentially visualize, for example, plasma wakefield accelerators, optical rogue waves or fast ignitor pulses, light-velocity objects, whose detailed space-time dynamics are known only through intensive computer simulations.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, University of Texas at Austin, 1 University Station, C1600, 2512 Speedway, Austin, Texas 78712-1081, USA.

ABSTRACT
Tomography--cross-sectional imaging based on measuring radiation transmitted through an object along different directions--enables non-invasive imaging of hidden stationary objects, such as internal bodily organs, from their sequentially measured projections. Here we adapt tomographic methods to visualize--in one laser shot--the instantaneous structure and evolution of a laser-induced object propagating through a transparent Kerr medium. We reconstruct 'movies' of a laser pulse's diffraction, self-focusing and filamentation from phase 'streaks' imprinted onto probe pulses that cross the main pulse's path simultaneously at different angles. Multiple probes are generated and detected compactly and simply, making the system robust, easy to align and adaptable to many problems. Our technique could potentially visualize, for example, plasma wakefield accelerators, optical rogue waves or fast ignitor pulses, light-velocity objects, whose detailed space-time dynamics are known only through intensive computer simulations.

No MeSH data available.


Related in: MedlinePlus

Analysis of phantom simulations.(a) Peak Δn of the Gaussian ‘dot’ versus evolution time tob=zob/vob, demonstrating interframe resolution; (b,c) lineouts at tob=7.3 ps (that is, zob=1.5 mm) of the rectangle along  (b) and xob (c), demonstrating intraframe resolution. Curves in a–c refer to phantom simulations in Fig. 2: original object (black dotted curve) and reconstructions with 19 (blue solid curve), 18 (red dashed curve) and 5 (green dash-dot curve) probes. (d) Normalized root mean square error of the same three tomographic reconstructions versus iteration number.
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f3: Analysis of phantom simulations.(a) Peak Δn of the Gaussian ‘dot’ versus evolution time tob=zob/vob, demonstrating interframe resolution; (b,c) lineouts at tob=7.3 ps (that is, zob=1.5 mm) of the rectangle along (b) and xob (c), demonstrating intraframe resolution. Curves in a–c refer to phantom simulations in Fig. 2: original object (black dotted curve) and reconstructions with 19 (blue solid curve), 18 (red dashed curve) and 5 (green dash-dot curve) probes. (d) Normalized root mean square error of the same three tomographic reconstructions versus iteration number.

Mentions: Figure 2a shows selected 2D (xob versus ) snapshots of an artificial phantom index object at seven different times tob (listed along the top) after entering a medium. These times correspond to object centre positions ranging from entrance (zob=0) to exit (zob=3 mm) of the medium. The horizontal spatial scale of each snapshot denotes , with the object’s leading edge (analogous to the head of Muybridge’s horse) to the right along the propagation direction zob. The phantom does not evolve by a real physical process, although some of its general features (for example, propagation length, xob and dimensions, evolution speed) were chosen to resemble those that occur in experiments below. The phantom’s detailed features were chosen to illustrate resolution limits, and to evaluate reconstruction artefacts, more effectively than a real physical process. Specifically, the object starts as a hollow rectangle with thin boundaries of widths Δ=2 μm (left and right) and Δx0=5 μm (top and bottom), as shown by dotted curves in Fig. 3b,c, respectively. Such a thin rectangle separately and stringently tests transverse and longitudinal resolution limits. As it propagates at vob=0.68c, chosen to equal pump group velocity in experiments, the rectangle narrows along xob over 0<tob<7.3 ps, thus mimicking self-focusing observed in those experiments. During a short transition period (tob~7.3±0.2 ps), a ‘dot’ of Gaussian profile appears to the lower left of the rectangle, quickly grows to Δnmax and falls to 0.2Δnmax (Fig. 3a, dotted curve), mimicking the time scale of plasma generation and partial recombination in the experiments. As the dot grows within an interval (~100 fs) comparable to the object’s duration Δ/vob, it tests interframe resolution. By breaking axial symmetry, it also tests the algorithm’s ability to reconstruct objects without prior assumptions about symmetry. The narrowed rectangle then expands longitudinally over 7.3 ps<tob<14 ps, mimicking group-velocity stretching of a laser pulse.


Single-shot tomographic movies of evolving light-velocity objects.

Li Z, Zgadzaj R, Wang X, Chang YY, Downer MC - Nat Commun (2014)

Analysis of phantom simulations.(a) Peak Δn of the Gaussian ‘dot’ versus evolution time tob=zob/vob, demonstrating interframe resolution; (b,c) lineouts at tob=7.3 ps (that is, zob=1.5 mm) of the rectangle along  (b) and xob (c), demonstrating intraframe resolution. Curves in a–c refer to phantom simulations in Fig. 2: original object (black dotted curve) and reconstructions with 19 (blue solid curve), 18 (red dashed curve) and 5 (green dash-dot curve) probes. (d) Normalized root mean square error of the same three tomographic reconstructions versus iteration number.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3921466&req=5

f3: Analysis of phantom simulations.(a) Peak Δn of the Gaussian ‘dot’ versus evolution time tob=zob/vob, demonstrating interframe resolution; (b,c) lineouts at tob=7.3 ps (that is, zob=1.5 mm) of the rectangle along (b) and xob (c), demonstrating intraframe resolution. Curves in a–c refer to phantom simulations in Fig. 2: original object (black dotted curve) and reconstructions with 19 (blue solid curve), 18 (red dashed curve) and 5 (green dash-dot curve) probes. (d) Normalized root mean square error of the same three tomographic reconstructions versus iteration number.
Mentions: Figure 2a shows selected 2D (xob versus ) snapshots of an artificial phantom index object at seven different times tob (listed along the top) after entering a medium. These times correspond to object centre positions ranging from entrance (zob=0) to exit (zob=3 mm) of the medium. The horizontal spatial scale of each snapshot denotes , with the object’s leading edge (analogous to the head of Muybridge’s horse) to the right along the propagation direction zob. The phantom does not evolve by a real physical process, although some of its general features (for example, propagation length, xob and dimensions, evolution speed) were chosen to resemble those that occur in experiments below. The phantom’s detailed features were chosen to illustrate resolution limits, and to evaluate reconstruction artefacts, more effectively than a real physical process. Specifically, the object starts as a hollow rectangle with thin boundaries of widths Δ=2 μm (left and right) and Δx0=5 μm (top and bottom), as shown by dotted curves in Fig. 3b,c, respectively. Such a thin rectangle separately and stringently tests transverse and longitudinal resolution limits. As it propagates at vob=0.68c, chosen to equal pump group velocity in experiments, the rectangle narrows along xob over 0<tob<7.3 ps, thus mimicking self-focusing observed in those experiments. During a short transition period (tob~7.3±0.2 ps), a ‘dot’ of Gaussian profile appears to the lower left of the rectangle, quickly grows to Δnmax and falls to 0.2Δnmax (Fig. 3a, dotted curve), mimicking the time scale of plasma generation and partial recombination in the experiments. As the dot grows within an interval (~100 fs) comparable to the object’s duration Δ/vob, it tests interframe resolution. By breaking axial symmetry, it also tests the algorithm’s ability to reconstruct objects without prior assumptions about symmetry. The narrowed rectangle then expands longitudinally over 7.3 ps<tob<14 ps, mimicking group-velocity stretching of a laser pulse.

Bottom Line: Tomography--cross-sectional imaging based on measuring radiation transmitted through an object along different directions--enables non-invasive imaging of hidden stationary objects, such as internal bodily organs, from their sequentially measured projections.Here we adapt tomographic methods to visualize--in one laser shot--the instantaneous structure and evolution of a laser-induced object propagating through a transparent Kerr medium.Our technique could potentially visualize, for example, plasma wakefield accelerators, optical rogue waves or fast ignitor pulses, light-velocity objects, whose detailed space-time dynamics are known only through intensive computer simulations.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, University of Texas at Austin, 1 University Station, C1600, 2512 Speedway, Austin, Texas 78712-1081, USA.

ABSTRACT
Tomography--cross-sectional imaging based on measuring radiation transmitted through an object along different directions--enables non-invasive imaging of hidden stationary objects, such as internal bodily organs, from their sequentially measured projections. Here we adapt tomographic methods to visualize--in one laser shot--the instantaneous structure and evolution of a laser-induced object propagating through a transparent Kerr medium. We reconstruct 'movies' of a laser pulse's diffraction, self-focusing and filamentation from phase 'streaks' imprinted onto probe pulses that cross the main pulse's path simultaneously at different angles. Multiple probes are generated and detected compactly and simply, making the system robust, easy to align and adaptable to many problems. Our technique could potentially visualize, for example, plasma wakefield accelerators, optical rogue waves or fast ignitor pulses, light-velocity objects, whose detailed space-time dynamics are known only through intensive computer simulations.

No MeSH data available.


Related in: MedlinePlus