Furthermore, by considering the case of a resonant gain, we show that these anomalies must always emerge in pairs, and each of them is surrounded by a phase vortex, producing a scattered field of diverging amplitude and undefined phase, which makes them analogous to phase singularities observed in perfectly absorbing structures. In contrast to these reports, the anomalies discussed in this work result from interference effects caused by gain-induced phase alteration, leading to trapping of light inside the gain medium. These anomalies resemble sharp resonances associated with lasing thresholds, studied over the past decades in various gain-doped dielectric structures, ,, ,, ,, ,. While even with gain, each particle is a weak scatterer with response dominated by radiative loss, and their optical response is significantly modified in arrays, where the interplay of gain, loss, and interference gives rise to scattering anomalies. Contrary to our previous findings on arrays of plasmonic nanoparticles with a shell of gain, the scatterers considered here are not resonant by means of localized plasmon or Mie resonances but only due to a spectrally dependent gain medium. We study this system using a Green function method, ,, ,, which includes the coherent retarded electrodynamic coupling between all particles, and radiative damping as the essential ingredient. In this work, we theoretically demonstrate the existence of scattering anomalies embedded in the band structure of simple diffractive arrays of identical dielectric nanoparticles ( Figure 1, left) that are intrinsically weakly scattering, but imbued with a weak frequency-dependent gain. The interplay between gain and loss gives rise to many scattering anomalies, such as unidirectional invisibility, coherent perfect absorber-lasers, as well as manifestations of parity–time (PT) symmetry, ,, offering a platform for active control of light propagation, , and for enhanced light-matter interactions,. For instance, properly engineered gain and loss could overcome efficiency barriers of metasurfaces for wavefront transformation imposed by impedance mismatch, , mitigate constraints on electric and magnetic optical response of matter, , and control the scattering by small ensembles of nano-objects. Recent theoretical works suggest that, apart from lasing, the role of gain could be far more nontrivial. These studies largely relate to the notion of combining gain with surface lattice resonances, in which Rayleigh anomalies and plasmon particle resonances hybridize. Recently, extensive research has been devoted to combining metasurfaces with gain media, with the main focus on distributed feedback lasing and diffractive outcoupling in plasmonic and dielectric nanoparticle arrays. Hypothetical Planets and Earth’s Second MoonīECOME AN X SUBSCRIBER AND GET EVEN MORE GREAT PODCASTS AND MONTHLY SPECIALS FROM MICAH HANKS.Electromagnetic metasurfaces are two-dimensional (2D) arrays of scatterers used to control amplitude, phase, and polarization of reflected, transmitted, and diffracted electromagnetic waves,.Lunascan Project Page on the Blair Cuspids.The Blair Cuspids: A Legitimate Lunar Anomaly?.‘More People Believe in UFOs Than Believe in Congress,’: Congressman at Denver UFO Symposium.The Pentagon Just Revealed the New Name of Its UAP Investigative Office.NEWS: Videos show massive bright light seen across Texas skies fireball also seen in 2 other states. Gumball: Advertise with The Micah Hanks Program Show Notesīelow are links to stories and other content featured in this episode: If you would like to advertise with The Micah Hanks Program, all you have to do is click the link below to get started: We have partnered with the fine folks at Gumball to handle our advertising/sponsorship requests. Want to advertise/sponsor The Micah Hanks Program? The story doesn’t end here… become an X Subscriber and get access to even more weekly content and monthly specials.Įnjoy The Micah Hanks Program? Check out Micah’s other podcasts here. Could there be more to the Moon and its many secrets than conventional astronomical thinking has taught us? This week on The Micah Hanks Program, we examine sightings of mysterious transient lunar phenomena (TLP) observed in locations like the Aristarchus crater, as well as a mysterious set of structures or “spires” that have caused debate for decades. Ranging from points of light, to mysterious colored bands, and even images since the dawn of the Space Age depicting curious structures, many have wondered if Earth’s Moon could be far more mysterious than most would ever contend. For centuries, astronomers have claimed to see strange lights and other phenomena on the Moon.
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