Newsgroup Feedback from alt.lasers on thread "adding a q-switch to a sharplan 3000"

(most spelling corrected)

 

  1. Anybody have any experience or suggestions on adding a Q-switch to a
    Sharplan model 3000 100 watt CW YAG. If so a decent source for a Q-switch
    with driver would also be helpful. If anyone has done this a few details
    would also be appreciated.

    Thanks

    Mitch

  2. Haven't done it yet, but I have a q-switch and driver for a similar project
    with a laser photonics 100 watt yag.  You might still be able to get the
    27mhz water cooled q-switches from resources unlimited for $225 NOS, which
    is an order of magnitude less than they cost new originally.  They sold out
    of the drivers long ago, but I think with a good ARRL handbook and a
    soldering iron you could build a broadband 50 to 100 watt rf amp and feed it
    with a 1 watt oscillator source using a power op-amp.  This was going to be
    my approach before I lucked out on the factory built driver.

    From Richard

3.     you DO realize, I assume, that the sharplan has a VERY short cavity, so the
        output has a low brightness, i.e. low focus ability... if your looking to do
        marking, etc, and want to take advantage of the power of your yag, simply
        adding a q switch isn't going to be enough, you would want to go with a
        longer length resonator (and possibly an aperture) to boot

        from Bob


4.     How would I go about getting a longer resonator. and how long?  Isn't 100
        watts 100 watts? as for the aperture do you mean changing or modifying it to
        a larger size? if so to what fiber size would be best?

        Thanks for the input

        Mitch


5.    100 W has nothing directly to do with the resonator length, only the YAG rod
        size and pump power.  In principle, you could remove the HR mirror and extend
        the cavity (or by some other means).  But doing this and adding an intracavity
        aperture to improve the mode structure isn't a trivial thing to do if you
        aren't experienced in this sort of thing.  And, you'll probably lose some
        power in the process.

        Sam Goldwasser


6.     How much would I need to extend the length to make a difference. the
        addition of an aperture, would that be on the back end (opposite the
        business end) what exactly is it and is its function. Although unfamiliar
        with allot of terms I do learn really fast. if I remove the HR mirror would
        I not need a mirror there at some point. I am looking to cut stainless
        stencils .003" thick and some marking with this thing. am I barking up the
        wrong tree??

        Thanks for the help

        Mitch


7.     As I mentioned, I want to do the exact same thing (extend cavity and add
        q-switch) to my 100 watt yag.  I just have about 4x10^26 projects ahead of
        it.

        I would be interested to hear how your experiments go.  I believe you are
        going to need a new mirror for the one that is not flat (or possibly both of
        them are concave if it is a hemispherical resonator).  I have not taken mine
        out of the mounts yet to test them...I guess that would be something to do
        on a rainy day.

        For cutting stainless stencils (I want to do the same thing to make gobos)
        you might want to look for a 100 watt CO2 laser if you can find one cheap
        enough.  You could also do some decent marking with that.

        From Richard


8.     I will keep the group up to date on tests. As for marking, I have a 40 watt
        co2 engraver that I am a distributor for. (low cost import complete machine
        also available in 60 watt)

        I must be missing something.. what would extending the resonator length
        actually accomplish. ( I assume basically moving the HR mirror further away
        from the cavity) how much further back. This machine has a HE-NE pointer
        laser is added at the rear, would I lose that one?

        Mitch


9.     when it comes to practical applications for lasers, such as cutting .003"
        stainless, I'm not the right person to give you any guidance.. when you
        said you wanted to ass a q-switch I had assumed you were interested in
        building a marker...

        a really quick condensed version of lasers 101...

        when you increase the cavity length of your resonator, you effectively
        increase (up to a certain point) the TEM00 mode size inside the rod... by
        increasing the mode size, you allow more of the pump energy going into your
        laser to be transferred into the tem00 mode volume.... basically tem00 is a
        type of laser operation that allows for very fine focusing of the laser
        beam. to put things in perspective, look at the quantronix 116 laser, a
        common laser used for marking applications... with no aperture in the laser,
        it might put out 70w of power.... put an aperture into the laser for tem00
        operation, and it might only put out 12w of power, but that 12w will eat
        into things allot better, because even though you only have 20% of the power
        left, you have a spot size that's 1/20th the size of the high power beam...
        since power density scales with r squared you have 100 times the power
        density on target, making the laser eat into hard materials ALLOT better...

        short cavities, but their nature aren't capable of putting out allot of
        tem00.. you COULD just put an aperture into the cavity to get a well
        focusable beam, but doing so would reduce your output power tremendously...
        if you lengthened the cavity you can recoup allot of that power loss....

        as Sam pointed out it isn't exactly a trivial thing to do, but if you have
        access to machine tools, it shouldn't be THAT hard to do... the hard part
        would be making the new laser stable so that you didn't have to tweak it all
        the time

        From Bob


10.   Thanks Bob great info.  How much longer would I have to extend the resonator
        and still have a stable laser. Essentially I assume that I have to move all
        the rear optics back and keep things in line. I do have a mill, lathe and
        CNC machine in my basement so fabrication won't be a problem.
        My understanding (correct me if wrong) is I have to change the rear HR
        mirror to a flat one (assuming concave) and extend the optical platform. At
        this point is where I would add the q switch and then the mirror? what of
        this conversion is really sensitive (or dangerous to the laser itself) would
        I have to change the front mirror as well??  and yes I would use this for
        marking as well. Stencil use is for my business, I pay too much for PCB
        solder paste stencils for my circuit boards.
        just a note: I paid $3500.00 for this and know it has less than 500 hours on
        it. Other than the fabrication what am I looking at for component cost to
        extend the cavity( curious). Is there somewhere where there is a drawing or
        more info on extending the resonator?

        Thanks again

        Mitch


11.    your not likely to find a simple 'how to' to do such a thing.. generically a
        flat / moderately long radius of curvature is the safest bet when building up
        a laser and just 'putting things together'... the easiest thing for you to
        do would be to set up the laser on an adjustable rail so that you could
        slide components up and down... I know Newport rails come for sale on ebay
        from time to time.. one thing you want to watch out for is that your rail
        should be at least about 3/4 or 1" thick to avoid flexure.. also if you
        are building up a rail on your own,. look for an alloy of aluminum that has
        the lowest coefficient of thermal expansion, and the lowest creep possible...
        one easier solution for you might be to watch out for a laser applications
        laser on ebay... if you pick up the head form such laser you will get a
        nifty little invar resonator... the set up is much too short just like your
        current laser, but if you watch out for a dead lexel laser head, allot of
        the lexels use invar resonators as well... by using the mirror mounts out of
        a laser applications laser, and the much longer invar rods out of something
        like an lexel 95, you would end up with a nice, sturdy invar resonator, of a
        much longer, and appropriate length.. if you want to build something up
        yourself, figure between 30" and a meter... although if you have your
        choice, I would err to the 1 meter end... the  quantronix 116 lasers use a
        short resonator (i.e. in lumonics lightwritters) and tem00 efficiency suffers a
        bit as a result...

        Bob


12.    Ok now I'm awake

        3/4" x 36" invar 36 rods cost is 760.00 cdn or 500 usd.

        To the point. The resonator in the Sharplan has 3pcs 3/4" dia by approx 18"
        long of what look  like fiberglass rods holding the whole thing together
        there is no optical rail like I have seen in some lasers. Would I replace
        the glass rods with the longer Invar rods and space things out and realign
        the package. like move the cold end back 16" and leave the hot end alone. or
        is there additional work to do on the hot end. Would just taking what I have
        and reassembling it on the longer invar rods suffice without replacing
        optics (mirrors etc). and just adding the q switch.

        Great place for info..Thanks to all who help on this project.

        Mitch


13.    Hot end and cold end?   I have never heard it expressed quite like that...
        :-)

        I would abandon the invar rod extension idea unless someone just gives you
        some out of a large frame argon or something.  You said you have machinery
        on hand?    You could probably make all of your mounts then.

        Here is an idea.   Grab a piece of 1/2 thick 3 inch wide 36 inch long
        precision ground steel from MSC industrial.  Buy a 36 inch long thk linear
        box rail with 4 or 5 ball bearing slides (see these all the time on ebay..I
        just sold some myself).  Bolt the linear rail to the steel plate and presto!
        you have a precision optical rail with x number of linearly adjustable
        mounts.  The only hard machining would be the optic mounts to attach to the
        THK slides.

        I would do something like this for mine, except that I scrounged a 30 inch
        long dovetailed optical rail with 4 x-y adjustable mounts from a dye laser a
        few months back and I plan to adapt that to my yag cavity extension project.
        YCEP
        :-)

        Richard


14.    Thanks Richard

        Hot end, cold end sounded about right.

        Anyway if I just used round rods to replace the current fiberglass rods and
        used all existing mounts and hardware I would only have to fabricate a mount
        for the q-switch. The cost of the Invar although high is not restrictive and
        seems it would make final alignment far easier as all the existing
        components are set up to mount on the round rods. Would moving the "cold
        end" back the 16" suffice for a better TEM albeit with some acceptable power
        loss?? also the front "hot" end would I have to change anything there. Are
        the existing mirrors ok for this "conversion"

        Mitch


15.    That's the big question I have had too...are the existing mirrors ok for the
        extension conversion.  I would say yes if they are both Plano Plano,
        possibly if one is Plano Plano and the other Plano concave with a long focal
        length, and no if both are Plano concave.

        I guess it is time to shine a collimated hene at each mirror and try to
        determine the focal length....

        Richard


16.    Richard

        what about the addition of 16" in length??

        Mitch


17.    for the price of buying the invar, you could probably pick up a control 512
        or similar rail based laser on ebay.... hell for that price you could even
        get a head along with the deal..

        Bob


18.    Well I have what I have and want to utilize it, Its complete with power supply, cooling, Safety interlocks I can reuse in a new cabinet and I want a little simplicity.

From what I understand, I need to lengthen the resonator. All parts are currently attached to very well machined mounts that happen to be riding on fiberglass rods. I believe I understand that with everything already mounted on heavy machined bracketry I would only have to transfer it to longer rods whatever they may be (invar, Inconel or ground machine stock) Providing the mirrors are of the right type, I should be good to go. If I am missing something or am incorrect in the above, someone kindly indicate so. (will 16" longer make a real difference {second guessing myself})

Thanks

Mitch


19.    

There is nothing magical about the Invar rods, other than their thermal expansion properties. Just crank up the lathe and turn some steel rods to the right length at least for your initial testing. They are just worried about that fact that you will have to constantly tweak the resonator mirrors, but who cares at this stage of the project?

Richard


20.    This is not a cost issue. If it will save me time (=money) and grief
        (=motivation) and end up with better stability I will use the invar rods.

        My question is "will the 16 inches I will be adding to the resonator length
        make a really big difference?? is there anything I am missing?

        I prefer simple solutions to complex problems. but want to be aware of what
        snags I will run into. Other than realigning the optics (assuming I use the
        rods and not a rail) and the slim possibility I need a mirror any other
        surprises to expect?

        Heading for the tool box but first have to get this 462 pound beast into the
        basement.

        Mitch


21.    I'm not sure the main issue was addressed: Are you experienced enough with
        working inside YAG lasers to be able to not only do the machining - which
        is the easy part - but to be able to select and test optics for optimal
        performance, do alignment, etc.  The beam is totally invisible and reflections
        are vision if not other hazards.  You will have to wear goggles at all times
        and use a laser power meter for maximizing power, Zapit paper or a beam
        profiler for beam quality.  This is all non-trivial - a lot more non-trivial
        IMO than Bob makes it sound.  He has many years of experience and sometimes
        assumes everyone else does as well.

        My apologies if you've already done this 25 times.  The basic questions would
        indicate otherwise, however.

         Sam Goldwasser


22.    I have not done this before and appreciate the hazards associated with it.
        No I do not have the experience to choose the necessary optics but I am good
        at doing the research to assist me in doing so. I also have the assistance
        of the Laser company who sold and maintained this machine to the Hospital I
        bought it from. As for aligning the optics, I have done this only with CO2
        systems and have never touched a yag system. As for components, The company
        that makes the CO2 laser engravers I sell makes all the necessary mirrors,
        lenses for YAG systems that I would require (I have engineering assistance
        available there as well albeit in Chinese). I only have a full understanding
        of the system components themselves and have learned allot from this one day
        on this forum. There is a wealth of information available from those that
        ask the questions and the quick response from those that truly know the
        answers. Sam's FAQ website is also helpful and surely throughout his site
        does his utmost to define SAFETY. Although I Know little of the project I am
        undertaking I am confident knowing that if I have a question, it will be
        answered by those who understand the "black magic" side of lasers. I am an
        RF engineer by trade and develop/manufacture some of the worlds smallest
        surveillance equipment used by governments worldwide. The black magic
        associated with rf is on a lower plane compared to the knowledge of
        understanding these "LASER" machines. Anyway I have ranted enough, time to
        take a good look at my project.

        Question for Sam  If I only extend my resonator and still use all existing
        components (manufacture nothing assuming my mirrors are flat) will setup be
        as difficult as you propose and will this really make a difference in the
        TEM of the laser?

        Thanks

        Mitch


23.    
        TSG wrote in message ...
        >I have not done this before and appreciate the hazards associated with it.
        >No I do not have the experience to choose the necessary optics but I am
        good
        >at doing the research to assist me in doing so. I also have the assistance
        >of the Laser company who sold and maintained this machine to the Hospital I
        >bought it from.

        if it's a laser service company, and not the actual OEM of the laser, I
        wouldn't rely on them for allot of help.... IMHO

        As for aligning the optics, I have done this only with CO2
        >systems and have never touched a yag system. As for components, The company
        >that makes the CO2 laser engravers I sell makes all the necessary mirrors,
        >lenses for YAG systems that I would require

        are you sure? if the company only sells co2 laser, there is no reason for
        them to have any yag optics for you, as the two are TOTALLY different and not
        interchangeable

        >Question for Sam  If I only extend my resonator and still use all existing
        >components (manufacture nothing assuming my mirrors are flat) will setup be
        >as difficult as you propose and will this really make a difference in the
        >TEM of the laser?

        if you extend the length of your resonator, and use proper optics you WILL
        See a marked improvement in beam quality, and hence the ability to burn into
        stuff...

        as far as using existing components go, did you check to see what kind of
        radius of curvature your optics might have as Richard suggested? no way to
        get a definitive answer  on that issue unless you check :)

        also, if you just want to try fiddling around right now, one thing you could
        try doing is using a very small aperture in the existing resonator.... like
        I said before I'm not an applications guy, but a laser guy... for all I know
        a low brightness q switched laser will eat into thin metal... I would bet
        that it would NOT but that bet is simply based on my experience of how laser
        markers behave, not by actually trying to do what you are attempting....
        there are no commercial arc lamp pumped markers that I know of that have
        anywhere near the short resonator you have in your medical laser, so
        unfortunately I'd bet no one will be able to give you a definitive answer to
        these questions, it will be a trial and error sort of thing...

        finally, as Richard suggested, if cost isn't an issue, why not just buy a
        laser rail off of ebay? you could use your existing power supply and cooler,
        etc.... I have seen PLENTY of control 512's and the like on ebay, selling
        from anywhere from a few hundred $$ to a bit under a grand...
        you could easily get not only a fully adjustable rail, but the q switch you
        need by going this route than you could by buying invar stock... also keep
        in mind that you will need an aperture mount.. instead of having to machine
        one up, if you get a laser off of ebay, odds are if it has a q switch, it
        will already have an aperture...

        Bob


24.    Thanks Bob for the advice. The co2 manufacturer also makes YAGS, just didn't
        want to spend 16k for a q switched 65 watt complete plus 400lb shipping from
        Asia plus a cooler.
        I guess first I should see what it can do now, The fibers and lenses will be
        here Friday. the hospital forgot to ship with the laser and will play with
        it before I take it apart. It was fully certified for use in Sept 2002 by
        the manufacturers rep and as for the selling company, one of their techs
        think its neat what I want to do with this. He is sending me the full
        service manual for it. Once I check for the type of optics I guess that will
        give me a good idea. I do know this gives me the full power out of a 3 meter
        2.3mm fiber tested with a calibrated power meter just before shipping

        If you have any more advice, knowledge is power and I love to learn.

        Cheers and thanks again

        Mitch


25.    This is all non-trivial - a lot more non-trivial
        >IMO than Bob makes it sound.  He has many years of experience and sometimes
        >assumes everyone else does as well.

        I will admit that this stuff IS all nontrivial, but it also isn't out of
        reach for an amateur with allot of drive.... based upon the activity in this
        thread, I assume this guy has a bit of drive :)
        Bob


26.    I have spoken to the mfg rep and have been told the following

        The mirrors are flat, without software control of the resonator output power
        has been measured as high as 160 watts (is this possible power supply is
        208v single phase 37 amps)

        Based on this if I replace the 3 fiberglass rods now 18" in length to longer
        36" long rods( would it really make a big or small difference if I use
        hardened steel, aluminum or invar type rods) and move the HR section back 16
        inches this will "improve the TEM00 mode operation with a slight loss in
        total output power" The gain is in the focus ability of the final beam. From
        all this I have learned I require a power meter, ZapIt paper for alignment
        and testing and of course pay attention to safety. If I am extending the
        cavity I will obviously have to extend all the electrical component as well,
        Any truly special type of wire to use on the arc lamp wiring, everything
        else is low voltage. Also should I do a q-switch at this time or wait until
        I have this portion complete.

        Again, thanks to all for their input. I will set up a website with pictures
        of before during and after for those interested.

        Cheers
        Mitch


27.    TSG wrote in message ...
        >I have spoken to the mfg rep and have been told the following
        >
        >The mirrors are flat, without software control of the resonator output
        power
        >has been measured as high as 160 watts (is this possible power supply is
        >208v single phase 37 amps)
        >
        >Based on this if I replace the 4 fiberglass rods now 18" in length to
        longer
        >36" long rods

        are you sure they are fiberglass? I have never seen such in a laser before..
        I have seen invar, I have seen aluminum rails, and I have seen quarts and
        graphite tubes.. but never fiberglass


        >( would it really make a big or small difference if I use
        >hardened steel, aluminum or invar type rods)

        it depends on what you consider to be acceptable performance.. some types of
        aluminum alloy has allot of creep, i.e. if you temp cycle it the physical dims
        of the material will change slightly... you could, in theory, use ANY
        material for your resonator so long as it's modestly rigid.. hell you could
        use 2x4's if your in a temp and humidity controlled room
        

        >and move the HR section back 16
        >inches this will "improve the TEM00 mode operation with a slight loss in
        >total output power"

        it's not a 'slight' loss in output power.. like  I said, going from highly
        multimode to tem00 might cause a factor of 5 or 6 reduction in power... even
        though the power density on target will go up by a factor of 20 (at 1/6th
        original power). it depends allot on what you are working with...

        > The gain is in the focus ability of the final beam. From
        >all this I have learned I require a power meter, ZapIt paper for alignment
        >and testing and of course pay attention to safety.

        actually you don't use zap it on a cw laser... zap it turns into burn it on a
        cw laser (unless you have some way of rapidly turning the beam on and off
        like a shutter...
    
        for a cw laser you need to see the beam.. this can be down with an ire
        viewer, or an ir card.... most plastic ir cards are only good for very brief
        exposure to light.. there are some ceramic plates made that show ir light..
        some require activation by a uv lamp, and are quite cumbersome.. kentek
        sells a decent ir viewing ceramic plate.. it's about 200$ iirc, and can be
        used in modest power beams on a continuous basis...
        
        >If I am extending the
        >cavity I will obviously have to extend all the electrical component as
        well,
        >Any truly special type of wire to use on the arc lamp wiring, everything
        >else is low voltage. Also should I do a q-switch at this time or wait until
        >I have this portion complete.
        
        the arc lamp wires carry a 20 or so kv trigger spike, and a 1000v potential
        for about a second when the arc first strikes to rapidly 'inflate' the arc
        so that stable operation for the he map can commence with the least sputtering of
        lamp electrodes... insulate appropriately. keep in mind that lamp supplies are
        often current supplies, so if you accidentally short a lamp lead, the supply
        will try pushing as much voltage as required to carry what ever current
        setting the supply is at... awful nasty if you happen to be part of the
        circuit...

        >Again, thanks to all for their input. I will set up a website with pictures
        >of before during and after for those interested

        once again, I would strongly suggest the alternative of using your existing
        supply and look for a head / rail assembly on ebay.. if you aren't doing this
        as a 'for the fun of it' project there is no reason to spend more time,
        effort, and money than need be to use what you have...

        ALSO.. a flat resonator is highly unstable in a long resonator.. you
        will want to either get a radiused mirror to replace one of your existing
        mirrors, or make one hell of a good resonator (i.e. back to the invar)..
        .also.. it would be beneficial if you have a hene on an adjustable platform
        for this project...

        if I think of anything else you might need, I'll point it out..

        Bob


28.    Bob If  I use the micro on this machine I can set it for a 0.1s pulse at a
        lower power, will this work for Zapit?
        As for the existing rods, They are yellow, definitely not metal of any
        nature, The cut ends are rounded a little and not as smooth as the rod body.
        I will take some close up pictures of the inside and post them on my site
        later and provide a link here. As for the hene, it is integrated on the back
        of the rear mount with a brightness control. There are also 2 shutters, 1
        outside the resonator on the front before the fiber coupling to redirect the
        beam to the power meter and the second in front of the rear mirror between
        the cavity and the HR. Listed as safety device.

        Thanks

        Mitch


29.    TSG wrote in message ...
        >Bob If  I use the micro on this machine I can set it for a 0.1s pulse at a
        >lower power, will this work for Zapit?

        ir cards can be had for as little as 6$ from radio shack... they aren't
        anywhere nearly as good as a ceramic plate that can be kept in t he beam
        continuously, but it would probably be better than zap it



        >As for the existing rods, They are yellow, definitely not metal of any
        >nature, The cut ends are rounded a little and not as smooth as the rod
        body.
        >I will take some close up pictures of the inside and post them on my site
        >later and provide a link here. As for the hene, it is integrated on the back
        >of the rear mount with a brightness control. There are also 2 shutters, 1
        >outside the resonator on the front before the fiber coupling to redirect
        the
        >beam to the power meter and the second in front of the rear mirror between
        >the cavity and the HR. Listed as safety device.


        aren't you going to take the laser out of the existing enclosure to increase
        the cavity length? if so the existing hene isn't going to be of much use to
        you I assume... you will want something that is adjustable...

        Bob


30.    "bob" <nomail@nospam.com> writes:

        > ir cards can be had for as little as 6$ from radio shack... they aren't
        > anywhere nearly as good as a ceramic plate that can be kept in t he beam
        > continuously, but it would probably be better than zap it

        Except when the power goes up and drills a hole though the card. :)

Sam Goldwasser


31.    normally it doesn't take more than one burned card for a newbie to learn the
        'quick swirl' method of avoiding a hole in your ir card... unless the beam
        is VERY high powered :)

        Bob


32.    If it is not a cost issue, sell the medical yag and do what bob suggested
        and get a control 512 on ebay.  The only reason I could see for spending as
        much on converting a medical yag as buying a prebuilt unit would be the
        experience gained and bragging rights...either of those important to you?

        Me, I am doing it for the bragging rights...course I am also not going to
        spend $$$ for invar rods.

        Richard


33.    Website with pictures
        http://www3.sympatico.ca/sgvideo/

        Bob or Sam if you look what's holding the hene and rear mirrors on the
        resonator, it should not be a problem to move the whole thing back the 16".
        I also made a mistake, there are 3 fiberglass rods holding it together not
        4. After you look at the pics on the web please share your opinions. All
        others opinions welcome as well.

        Thanks

        Mitch


34.