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Laser enabled "Cloaking Device", Progress July 2018

Encap

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Star Trek screenwriter Paul Schneider, inspired in part by the 1958 film Run Silent, Run Deep, imagined cloaking as a space-travel analog of a submarine submerging, and employed it in the 1966 Star Trek episode "Balance of Terror". Another Star Trek screenwriter, D.C. Fontana, coined the term cloaking device for the 1968 episode "The Enterprise Incident".

Fast Forwrd to July 2018:
"We propose a conceptually novel approach to the problem at hand, in the quest for realization of full-field broadband invisibility. For this purpose, we use reversible transformations of the illumination energy spectrum, allowing us to tailor at will the interaction between a wave and an object
A customized and reversible redistribution of the illumination frequency content, allowing the wave to propagate through the object of interest while preventing any interaction between the wave and the object"
"In recent years, a variety of interesting concepts have been proposed to enable the concealment of objects from detection or observation, including invisibility cloaking. For an object to remain truly transparent to an illumination wave, a cloak must restore the exact spatio-temporal profile of the wave, including both amplitude and phase variations across the entire illumination frequency spectrum, i.e., the full field.
In this work, we propose a new conceptual approach to the problem, enabling the realization of full-field broadband invisibility, experimentally demonstrated here for the first time to the best of our knowledge"
From July 2018 issue of The Optical Society of America publication OPTICA: https://www.osapublishing.org/optica/fulltext.cfm?uri=optica-5-7-779&id=394935


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Fig. 1. Broadband invisibility cloaking through reversible wave-spectrum control. (a) Detection of a target (object) through the signature imprinted on the spectrum of a broadband wave (represents frequency). For simplicity of illustration, only backscattering (reflection) of the wave by the target is considered. (b) Concealing of the target by reversible transformations of the wave spectrum. (c) Numerical simulation of the proposed spectral cloak, operating on an illumination wave with a broadband continuous spectrum (solid blue curves, 2D representation) and a frequency comb (dashed red curves). Although the effect of PM occurs instantly, here it is depicted as a progressive process (2D representation) in order to reveal the intricate mechanism leading to the formation, and subsequent reversal, of the frequency gaps.
 
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Singlemode Laser

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Nice find! I just don't understand why they call it broadband. The frequency comb used has discrete frequencies, so a "zoom" into the spectrum should reveal the "cloaked" object. I assume they would need a true broadband source for a perfect cloak.

Singlemode
 

Encap

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Nice find! I just don't understand why they call it broadband. The frequency comb used has discrete frequencies, so a "zoom" into the spectrum should reveal the "cloaked" object. I assume they would need a true broadband source for a perfect cloak.

Singlemode

Was an oversight, I meant to include the reference from within the July 2018 issue of The Optical Society of America publication OPTICA in the OP--so here you go, also added it to the OP
See published article w. explanation and detailed data highlights here: https://www.osapublishing.org/optica/fulltext.cfm?uri=optica-5-7-779&id=394935
 
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Benm

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You might still be able to detect it when you look at extremely narrow wavelengths, but as i understand it not with a "normal" spectrometer that takes steps in the order of 1 nm or so.

If you "zoomed in" in on a reflected broadband spectrum to the pico- or femtometer level you could probably see that something is at least unusual.

Similar things happen with radio wave frequencies: if you have a good broad-spectrum signal you can (perhaps intentionally) keep it so low it appears under the noise floor to a uninformed observer but still decode it when you know exactly what to look for.

Practically this actually does happen with things like GSM signals in remote locations with very weak coverage: the basestation signal is so broad and spread out that it does not stand out from the noise floor, but you can still make a call or send and sms from that location.

I think something similar is happening here, but then at light frequencies instead of around 900/1800 MHz.
 




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