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  1.  
    Question primarily for Angus:

    Do materials exist which act on light differently depending on the incident direction? Here, I'm simply asking about two opposite directions: left-to-right or right-to-left.

    If such a material existed, then building a Q-multiplier for a laser or beamer would be easier. A plate of such a material would allow the transmission of light from the source laser to a distant mirror. The light reflected back from the distant mirror back at the plate would cause the plate to reflect it all back again, rather than transmitting it all through back onto the source laser. Clearly a useful property for a material to have.
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      CommentAuthorAngus
    • CommentTimeJun 11th 2016
     
    No material, but there are devices that can do this function. They are extensively used in optical telecommunication.

    https://en.wikipedia.org/wiki/Optical_isolator

    https://en.wikipedia.org/wiki/Optical_circulator

    The company I worked for at the turn of the century was a major manufacturer of such things and I had to deal with many patents and inventions in the area.
  2.  
    OK. So can it be used in the manner I described?

    I realise that phase coherence might be a showstopper.
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      CommentAuthorAngus
    • CommentTimeJun 11th 2016
     
    You'd have to describe your setup more precisely. These are devices usually attached to optical fibre inputs and outputs. Internally they require forming a collimated beam, splitting it into two beams with orthogonal polarisations, passing both through a sequence of crystals having large Verdet constants to get Faraday effect polarisation rotations, and then recombining the two beams and coupling back into the output fibre.

    They don't have any dependence on the coherence of the light or its polarisation (if you make them right). They operate over a fairly broad spectral range. They will have some power limitations set by the materials used.
  3.  
    I'm talking about the phased array beamer, oft-discussed here. If the returned beam can be back-reflected off a "magic plate" placed somewhere in front of the lasers, then the effective beam power can be increased. This prevents the beam from re-entering the source laser cavities.

    So can such a magic plate be made? It transmits in the forward direction and reflects in the other.
    •  
      CommentAuthorAngus
    • CommentTimeJun 12th 2016 edited
     
    That is generally what these things are used for in fibre systems, where back reflections destabilise the lasers.

    But you want something to put in a large high power beam rather than a fibre waveguide, so I gather. Briefly - my advice would be ... no. Too expensive, complex and fragile.

    The good news might be that if you know what the wavelength and polarisation are you can get away without a nonreciprocal device. You could use a quarter-wave plate (q.v.)

    This will keep reflections out of your laser. It won't work in the manner you describe, though. All these devices rotate the polarisation of the reflection so that you can keep it out of the laser. If you want to send it back into the cavity you go through the device again, which does another rotation, so that on the next pass the reflected light is returned to the original polarisation state and can get out of the cavity and into the laser.

    Gut feel tells me that what you want to do violates the Brightness Theorem, and therefore the Second Law of Thermodynamics.
  4.  
    Each individual laser in the array is about 1 KW. Does that help?
    •  
      CommentAuthorAngus
    • CommentTimeJun 12th 2016
     
    As I said, I think the whole idea violates the second law of thermodynamics by way of the brightness theorem.
  5.  
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      CommentAuthorAngus
    • CommentTimeJun 12th 2016
     
    I had seen that abstract before writing my previous post, to which I still adhere.
    •  
      CommentAuthormaryyugo
    • CommentTimeJun 12th 2016
     
    Posted By: AngusThe company I worked for at the turn of the century
    Which century?
    •  
      CommentAuthorAngus
    • CommentTimeJun 12th 2016
     
    Very droll...
  6.  
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      CommentAuthorAngus
    • CommentTimeSep 5th 2016 edited
     
    Miroshnichenko establishes the formula for the probability of a single - and no longer multiple - photon transition from a bound state of a quantum system to a state of continuous spectrum, using the so-called Markov approximation. This makes it possible to select the exposure time and the beam's intensity to obtain a narrow stripe in the photoresist on the substrate.


    (from the referenced article).

    Wow. It's tricky enough getting multiphoton processes to work. If you have to control exposure that closely it will be interesting to see if it can be made practical.
  7.  
    I wondered if it might impact photolithography as well as astronomy
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      CommentAuthorAngus
    • CommentTimeSep 5th 2016
     
    The stated application was photolithography.
  8.  
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      CommentAuthorAngus
    • CommentTimeAug 8th 2019
     
    Differences in refraction across the lens, as well as imperfections in its shape and materials, all contribute to some of those light rays, especially those entering the lens near its outer edges, missing the target. It’s a phenomenon known as spherical aberration


    No.
  9.  
    It is a very weird journalistic attempt at description of spherical aberration.
  10.  
    Seems to be what it purports to be - a formula that removes spherical aberration.