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    Default optics

    Ok I feel stupid asking this but you never know. Is there an optic that can take in a beam at an arbitrary angle and output it to a set other angle?

    I actually need to do this in reverse. Get a beam in at a fixed angle and then rotate it to some other angle. Sure a mirror but how to keep a lens lined up precisely with the reflected beam.

    Beam hits mirror and is reflected at an angle. I want to be able to move an arm and have the reflected beam track. I was thinking of some kind of gear to move the mirror backwards as the arm rotates So say the arm goes right the mirror would tilt left to compensate. Some kind of gearing. Make any sense at all? The idea is that I have a mirror on a micrometer at the end of this arm and I need to keep the beam squared up as the arm rotates to the beam reflected off the mirror. I also need to add a dichro and diode so I can use it for alignment. There are two arms that must meet precisely to form a sum difference and the focus has to be exact. Adding this allows me to align the IR beams and then focus them precisely. This has nothing to do with light shows.

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    ... there are some "multi-axis-arms" with prisms in the joints, which translate a collimated beam from input to the output ...

    Viktor
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    any links would be helpful

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    Quote Originally Posted by kecked View Post
    Ok I feel stupid asking this but you never know. Is there an optic that can take in a beam at an arbitrary angle and output it to a set other angle?

    I actually need to do this in reverse. Get a beam in at a fixed angle and then rotate it to some other angle. Sure a mirror but how to keep a lens lined up precisely with the reflected beam.

    Beam hits mirror and is reflected at an angle. I want to be able to move an arm and have the reflected beam track. I was thinking of some kind of gear to move the mirror backwards as the arm rotates So say the arm goes right the mirror would tilt left to compensate. Some kind of gearing. Make any sense at all? The idea is that I have a mirror on a micrometer at the end of this arm and I need to keep the beam squared up as the arm rotates to the beam reflected off the mirror. I also need to add a dichro and diode so I can use it for alignment. There are two arms that must meet precisely to form a sum difference and the focus has to be exact. Adding this allows me to align the IR beams and then focus them precisely. This has nothing to do with light shows.

    I believe your optic is a F1 lens on a translation stage and a couple of mirrors or prisms to feed two beams in, equidistance from the center of the lens. The whole lens and mirror set must move in unison. Its worked for me for doing LDV.
    https://www.google.com/search?q=lase...=1580159427288

    Can also be done with a big spherical mirror, if GVD or wavelength and coatings become a problem. You can then collect the scatter using a mask and the center of the lens /mirror, in some cases. If your SHG does not scatter but does form a beam, some changes may be needed. For pico/femto you may need mirrors, not a lens.

    Steve
    Attached Thumbnails Attached Thumbnails Multiphoton with one, two, many adjustments.png  

    SHG PARTY TIME many adjustments.png  

    Last edited by mixedgas; 01-27-2020 at 14:11.
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    Sum Frequency Generation of CO on (111) and Polycrystalline Platinum Electrode
    Surfaces: Evidence for SFG Invisible Surface CO
    Steve Baldelli,†,§ Nenad Markovic,§ Phil Ross,§ Yuen-Ron Shen,‡,§ and Gabor Somorjai*,†,§
    Departments of Chemistry and Physics, UniVersity of California at Berkeley, Berkeley, California 94720, and
    Materials Science DiVision, Lawrence Berkeley National Laboratory, Berkeley, California 94720
    ~

    Remember you may need an adjustable optical delay line in the path of one excitaion wavelength to ensure temporal overlap. 25 cm of travel comes to mind.
    The other way could use a pair of galvos in the same plane and adjust for signal, but that feels barbaric.


    Steve

    Last edited by mixedgas; 01-27-2020 at 12:45.
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    ... I was referring to this type of "mirror-joint-arm" ...

    Viktor
    Attached Thumbnails Attached Thumbnails Spiegelgelenk-Arm.png  

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    Once upon a time at a university three hours from us, I briefly worked on one of these, mostly diagnosing the control bus.
    Worth a look:

    https://ekspla.com/products/laser-spectroscopy/

    Our "Friend" ,my former boss, might send you a manual. The PI who has it may be friendly, but as the PI a former customer of said former employer , some rules in my NDA apply and I can't contact him 4 U. My former boss can.
    ~
    The methodology of that one is very software dependent. Amazing machine.



    Steve
    Last edited by mixedgas; 01-27-2020 at 14:15.
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    Steve this is the picosecond sum difference experiment. I’m looking to shrink it down and path fold the delay line. Taking the topas out with the tsunami out. Need to path length Mach then overlap precisely on a sample to form a difference and summsignal. Aligning is insane so I want to make two arms I can pr3vusely control in regards to angle and then add a lens in each arm with a dichro visible diode so I can align and then micrometers onbtb3 Leone’s for precise focus. Now I want to add two or three bounce mirrors on one arm as a delay line where I change spacing to tune the phase. Now put that all Noder the stage and then replace out the topas and tsunami signals with your overdriven leds. If it works I replace that 250,000 setup and it fits in the palm of my hand.

  9. #9
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    Last time I looked at that problem while at Cee where are you, Professor Sierra was not telling me what signal I was looking for or what the polarizations should be. One target was the sample, which was to be behind a IR capable window and 40 uM of DI H2O for the 'lectrochemmisery. So I just remembered that I was going to split the beam system into a sort of Whetstone Bridge layout. The delay was outside the bridge. The idea was that if the whole mess was built on a mahoosive large dimeter Invar rod from the scrapped dye laser with exactly the same optics, you'd have twenty -forty minutes between re-aligns to cycle through wavelengths on the tunable laser.

    One arm was the reference with something thin and highly non-linear, to peak the time delay. Then I would do the knowingly painful process of making the sample arm aligned at nearly the same optical distances (Today I'd do that with a surplus HP distance measuring interferometer from Sam G and build the system on a quartz or Zeodur(tm) plate) and then if I could keep the reference arm non-linear I'd know I'd have a chance of having time alignment at the sample arm. Idea being that aligning just when there was a temperature change or just a few times a day was a way better idea then aligning all the time, while not knowing what I was looking for.

    I thought this to be far fetched and a original idea until the paper chase on Google found a paper where some other group had the same idea but had a much better budget for custom optics. The two distances from the beam splitters to samples need not be exact, they just needed to be a multiple of (N+M) wavelengths so the peaks from the two lasers were nearly matching , thus solving the simultaneous equation of N( Lambda 1 x D1 ) = M( Lambda 2 x D2) when M and N are integers of wavelengths or half wavelengths, in other words where good old Distance = Rate x Time solved for two distinct source laser wavelengths in the ring resulted in a peak overlap. There are a huge number of integer multiples in the beam path where you would have that peak. So for a given set of angles, the paths just need to be close in length but not exact.

    Basically would give me a poor man's FROG or
    GRENOUILLE* so I had a way of checking if I could possibly have a signal by checking the amplitude of the reference material light.

    Dang, today I know a heck of a lot more then I knew then. There is one tiny flaw, in that the two arms are not isolated from each other some way, you might end up with an interferometer. A waveplate in one arm would possibly cure that if it happened.


    *Grating-eliminated no-nonsense observation of ultrafast incident laser light e-fields

    Steve




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  10. #10
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    If you were just doing SHG, a Fresnel Biprism is the magic constant deviation prism optic with a beam crossover at a nearly constant point. . I've used them in a focusing interferometer to shoot gratings for the Air Force on a project using a Liquid Crystal material. One Biprism made the whole setup after the spatial filter.

    There are a couple of prisms with near constant deviation as you rotate them.

    Adding that second wavelength makes things a bit more complicated.


    Its taking a while to remember all this that you ask.

    Ribbit, Ribbit...:

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

    Steve
    Last edited by mixedgas; 01-27-2020 at 21:25.
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