Adam Smith\u27s First Amendment

Until recently, Washington, D.C., maintained what most would regard as a perfectly ordinary licensing scheme for tour guides. In 2014, the D.C. Circuit declared the scheme unconstitutional under the First Amendment in a remarkable case entitled Edwards v. District of Columbia. The court announced that the District\u27s regulations must be reviewed under intermediate scrutiny because they burden speech; the regulations made it illegal to talk about points of interest or the history of the city while escorting or guiding a person who paid you to do so without first obtaining a license. Licenses were awarded to those who passed a test and paid a $200 registration fee. After a rather scathing review, the court concluded that the regulations failed directly to advance the government\u27s interest in protecting D.C. tourism from dishonest or unsatisfactory tour guides. It found that the private market - operating through rating sites like Yelp and TripAdvisor - was instead sufficient to turn the coal of self-interest into a gem-like consumer experience, thereby rendering the District\u27s scheme superfluous

Visualization of the birth of an optical vortex using diffraction from a triangular aperture

Funding: EPSRC, UKThe study and application of optical vortices have gained significant prominence over the last two decades. An interesting challenge remains the determination of the azimuthal index (topological charge) l of an optical vortex beam for a range of applications. We explore the diffraction of such beams from a triangular aperture and observe that the form of the resultant diffraction pattern is dependent upon both the magnitude and sign of the azimuthal index and this is valid for both monochromatic and broadband light fields. For the first time we demonstrate that this behavior is related not only to the azimuthal index but crucially the Gouy phase component of the incident beam. In particular, we explore the far field diffraction pattern for incident fields incident upon a triangular aperture possessing non-integer values of the azimuthal index l. Such fields have a complex vortex structure. We are able to infer the birth of a vortex which occurs at half-integer values of l and explore its evolution by observations of the diffraction pattern. These results demonstrate the extended versatility of a triangular aperture for the study of optical vortices. (c) 2011 Optical Society of AmericaPublisher PDFPeer reviewe

Visualization of the birth of an optical vortex using diffraction from a triangular aperture

The study and application of optical vortices have gained significant prominence over the last two decades. An interesting challenge remains the determination of the azimuthal index (topological charge) l of an optical vortex beam for a range of applications. We explore the diffraction of such beams from a triangular aperture and observe that the form of the resultant diffraction pattern is dependent upon both the magnitude and sign of the azimuthal index and this is valid for both monochromatic and broadband light fields. For the first time we demonstrate that this behavior is related not only to the azimuthal index but crucially the Gouy phase component of the incident beam. In particular, we explore the far field diffraction pattern for incident fields incident upon a triangular aperture possessing non-integer values of the azimuthal index l. Such fields have a complex vortex structure. We are able to infer the birth of a vortex which occurs at half-integer values of l and explore its evolution by observations of the diffraction pattern. These results demonstrate the extended versatility of a triangular aperture for the study of optical vortices. (c) 2011 Optical Society of America</p

Visualization of the birth of an optical vortex using diffraction from a triangular aperture

The study and application of optical vortices have gained significant prominence over the last two decades. An interesting challenge remains the determination of the azimuthal index (topological charge) l of an optical vortex beam for a range of applications. We explore the diffraction of such beams from a triangular aperture and observe that the form of the resultant diffraction pattern is dependent upon both the magnitude and sign of the azimuthal index and this is valid for both monochromatic and broadband light fields. For the first time we demonstrate that this behavior is related not only to the azimuthal index but crucially the Gouy phase component of the incident beam. In particular, we explore the far field diffraction pattern for incident fields incident upon a triangular aperture possessing non-integer values of the azimuthal index l. Such fields have a complex vortex structure. We are able to infer the birth of a vortex which occurs at half-integer values of l and explore its evolution by observations of the diffraction pattern. These results demonstrate the extended versatility of a triangular aperture for the study of optical vortices. (c) 2011 Optical Society of America</p

Numerical Investigation Of Enhanced Femtosecond Supercontinuum Via A Weak Seed In Noble Gases

Numerical simulations are employed to elucidate the physics underlying the enhanced femtosecond supercontinuum generation previously observed during optical filamentation in noble gases and in the presence of a weak seed pulse. Simulations based on the metastable electronic state approach are shown not only to capture the qualitative features of the experiment, but also reveal the relation of the observed enhancement to recent developments in the area of sub-cycle engineering of filaments

Numerical investigation of enhanced femtosecond supercontinuum via a weak seed in noble gases

Numerical simulations are employed to elucidate the physics underlying the enhanced femtosecond supercontinuum generation previously observed during optical filamentation in noble gases and in the presence of a weak seed pulse. Simulations based on the metastable electronic state approach are shown not only to capture the qualitative features of the experiment, but also reveal the relation of the observed enhancement to recent developments in the area of sub-cycle engineering of filaments. (C) 2016 Optical Society of AmericaAir Force Office for Scientific Research [FA9550-13-1-0228]; National Science Foundation [ECCS-1202471, ECCS-1229563]Open access journal.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Visualization 1: Numerical investigation of enhanced femtosecond supercontinuum via a weak seed in noble gases

animation related to Fig. 6 Originally published in Optics Express on 27 June 2016 (oe-24-13-15110