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Thread: Ruby laser mirrors

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    Default Ruby laser mirrors

    I'm looking for ruby laser output couplers and HR mirrors. I'd also be very grateful if someone knows of a commercial source of new or used ruby laser optics. I've been searching the internet for a long time and I can find HR mirrors for 694 nm but cannot find output couplers.

    Thanks,
    Ron

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    All of the ruby lasers I've seen were smaller units that had either dielectric or silver mirrors bonded to the ends of the rod. I'm guessing that you're building (or repairing) a larger unit, then?

    I've read about ruby lasers with external optics before (including an 8-lamp monster that was cooled with liquid nitrogen!), but I've never seen any in real life.

    Have you tried contacting Semrock? They have a large catalog of pre-made mirrors and dichros, but they are also willing to do short runs of custom optics - for a price of course! I would expect that the ruby line (694nm) would be common enough that they would have something in their catalog that would work...

    Adam

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    Adam,
    Thank you for your response. I sent an email to the company you suggested.

    I am building a ruby laser from parts and the only major components I don't have are the mirrors.

    Ron

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    Quote Originally Posted by rcbaktis View Post
    Adam,
    Thank you for your response. I sent an email to the company you suggested.

    I am building a ruby laser from parts and the only major components I don't have are the mirrors.

    Ron
    chose well as silver for example will last 1-5 shots max

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    Get started with a Krypton Ion OC, or gulp, a Alexandrite / or low nm range Ti Saph OC, but Alex has far more gain than ruby, so the transmission may be too high.

    676 is not far from 694, usually Ion laser OCs have a design bandwidth and moderate transmission slope flatness at least 30 nm outside their design range.

    Otherwise, you are looking for un-obtainium or a custom coated optic.

    Like from these folks:

    About us | Markets, Portfolio, Production & References (pgo-online.com)

    They are one of the few who will run a single optic. At least they used to claim one offs.

    One of the problems of asking for custom coatings, is if you don't know the single pass gain, desired radius, and stored energy details of your rod, no one will want to coat for you as a hobbyist. Been there, done that, and have the Tee Shirt. Many optics producers have been sued when cavity optics design goes wrong, thus ending with damage on a high power rod, so... usually the answer is NYET!

    A long radius, hard coated, SP 124 or 125 sized , HENE OC mirror might work, but certainly would not have much transmission and may not release enough energy to protect the rod. Unless you have a Q-Switch, you may find that long pulses and Ruby rods don't get along well, due to heating of the faces / thermal lensing. Keep the rep rate down to 10s of seconds, if not minutes, or more when testing, else thermal lensing/breaking . Al2O3 does not conduct heat well.

    Random mirrors won't help you. This takes some calculations, and, in your case, assumptions on your rod's original use, was it an oscillator or amplifier when designed? Doping will be less for the amplifier rod.

    You can search Ebay for Ruby parts / optics from JK Lasers in Rugby UK till the Cows go home, and not ever find one. I worked on a one oscillator two amplifier JK for a few months maybe 10 (or was it 110?) years ago.

    Good luck, that is a TOUGH problem. How long is this rod?

    There is this guy, Anderson Lasers, Inc - Main Page , he liked oddball things like Ruby...

    Steve
    Last edited by mixedgas; 06-22-2022 at 18:00.
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    Steve,
    Thank you for your suggestions and information. I'm an engineer but new to lasers, so I appreciate the advise of those who are more experienced and knowledgeable. The rod I have appears to be in very good condition and is 6 mm X 76 mm, AR coated flat ends. I was told the doping is 0.05%. From the research I've been doing, it seems to be a common size. I have found several papers that detail the equations for calculating threshold but I'm not clear on how to get an accurate figure for gain and then use that to determine the optimum OC reflectivity. It seems that the calculations involve making some assumptions about losses. I have found some references that lead me to believe I could get by with a 50%R OC. Does this seem reasonable?

    I've been wanting to build a ruby laser since I was twelve years old. I'm close to retirement age now and I finally have the resources to pursue these dreams from my youth. I will soon have the time as well. There are many projects I have in mind. I will not be bored!

    Thank you,
    Ron

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    Steve, what is the typical mirror configuration for a ruby laser with external mirrors? Do they use a planar OC and a concave HR? Dual-concave? Or are both the HR and OC just flat, planar mirrors like you'd have when the mirrors are bonded to the rod ends?

    Adam

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    Usually if the rod is uncoated, it is a weakly convex or concave HR, and a long radius OC.

    Ruby systems tend to be designed for a highly optimized cavity to deal with immense thermal lensing. Sometimes their designers like negative numbers, thus will use a slightly convex HR. That is also common in master oscillators for amplified units.

    Since most systems are ancient, they tend to have conceptually difficult cavities, spinning prism Q-Switches, cavities folded with prisms, prism retroreflectors as HR, etc.

    His rod is the standard GEN II US ruby rangefinder size. So flat HR in the form of a retroreflector, and at one time, a resonant reflector output, which by definition is a stack of flats.

    If his rep rate is low, well. Nearly anything goes. So, a Flat and a Concave is always a good start, and thus the stability criterion becomes simple math. You can model that with the PSST! freeware.

    Psst! homepage (st-andrews.ac.uk)

    Flat-Flat:

    ADA032037.pdf (dtic.mil)


    This paper covers spherical mirrors.

    Single transverse and longitudinal mode Q-switched ruby laser




    More flat-flat:

    215288853.pdf (core.ac.uk)

    Flat looking rod ends are not always flat, either.

    from what I can find he needs between 30 and 50% transmission depending on the rod. That dual plate resonant reflector starts looking very good, as the spacing does not need to be that precise.. Nearly all papers I found had resonant reflectors because the coating technology just wasn't there yet.
    Intracavity loss measurements show between 1 and 11% from various papers. The later the rod was made, the lower the internal scattering, approaching 1% at the end of the ruby Epoch.

    Some light reading:
    10394_7189.PDF (dur.ac.uk)

    Has a short segment on OCs.

    Drop an Email to Scientific Materials inc. They made/make a ton of rods, including many, many early ruby rods.. I don't know how friendly they will be since FLIR bought them in the past two years/

    sales@scientificmaterials.com



    Steve
    Last edited by mixedgas; 06-24-2022 at 10:27.
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  9. #9
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    Thank you to everyone who has replied. I really appreciate it.

    I found an OC at Laser Components (laser-components.com). Here are the specs:

    PR500-1000/50/AR PW0512UV
    Output coupler, side 1 R=50% +/- 3% @500-1000 nm, side 2 R<1% avg. 500-1000 nm
    12.7 mm diameter, 3.2 mm thickness, fused silica
    Price=$410.00 ea.

    It's broadband but the ruby laser wavelength is comfortably near the center of the band. The salesman said I could call and order with a credit card, and I was tempted. I haven't bought it yet because I would prefer to find a cheaper solution. I also would like to learn more about etalons and how they can be used in place of a traditional mirror, as was suggested in one of the replies to my post, so I'm doing more research on them. It's not just about having a cool laser, it's about the process and learning as much as I can.

    Ron

  10. #10
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    The patent contains all the construction details for the resonant mirror / stack of etalons.

    Steve
    Attached Files Attached Files
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