561nm Yellow YAG (?) from Lumenis Varia Eye Laser

Here is a photo from the 561nm "yellow" section of a Lumenis Varia Tri-Color Laser, the machine this element came out of was rated at 600mw of yellow output.



Photo of what appears to be a YAG from this section:



I believe this crystal is a square YAG which appears to be side diode pumped, if that is what it is, does anyone here know if these can be pumped with a common IR bar diode? The photo appears to show the crystal is being directly pumped that way but at what wavelength?

Edit: Lumenis calls 561nm "yellow" but it looks more green than yellow to me: Lumenis Novus Varia Red, Yellow, Green Tri Laser System | Laser Locators

See a color comparison here to 520nm: Relative Laser Beam Brightness Calculator: (520nm 1mw) vs. (561nm 1mw)

Re: 561nm Yellow YAG (?) from Lumens Varia Eye Laser

The YAG has heatsinking on only one side, so it was probably designed to be side-pumped. As for using a bar, isn't that what's side-pumping it in the photo?

Re: 561nm Yellow YAG (?) from Lumens Varia Eye Laser

Yep, sure appears to be a side pumped YAG, I have not seen a square YAG before and the bar diode looks similar to 808nm diode array. Trying to understand how they derive 561nm out of this YAG with that kind of diode, if that is what they are doing. I have a big hole in my knowledge regarding how this works.

Re: 561nm Yellow YAG (?) from Lumens Varia Eye Laser

Only one crystal? Or multiple crystals?

If only one, I would expect 1123nm possibly?

I have read through alot of crap on google about yellow wavelengths.... if you just google 561nm from YAG you get tons of stuff... but you never really know on those items unless you get part numbers and can actually research them or contact the company.

Re: 561nm Yellow YAG (?) from Lumens Varia Eye Laser

I know there is a 1123 line output from a ND YAG when flashed with a lamp which can be doubled with a crystal to produce 561nm (when using mirrors with the YAG to suppress 1064nm while being HR to 1123), but finding this unit side pumped with a diode surprised me, makes me wonder how they get 1123nm that way. I will continue researching this, I have the YAG, or what sure appears can be nothing other than a YAG, so want to start dreaming of a build for it.

Edit: I have very little information on how this was used, except the photo of the unit being side pumped, don't know if there might have been a thin crystal between the diode or not yet but I can't imagine that being done, since the output is yellow and not green. Is there such a thing as a 1123nm diode? I have never heard of one. I have tried contacting these companies in the past and made the mistake of letting them know I was a hobbyist, always crickets when I do that. Perhaps a different approach will work. They always seem to think I will shoot my eye out and go silent when I start talking about using their stuff in a hobby laser. I find laser professionals to be a bit too arrogant in that regard but then again, we treat newbies that way in the forum a lot too.

Re: 561nm Yellow YAG (?) from Lumens Varia Eye Laser

Alaskan said:

I know there is a 1123 line output from a ND YAG when flashed with a lamp which can be doubled with a crystal to produce 561nm (when using mirrors with the YAG to suppress 1064nm while being HR to 1123), but finding this unit side pumped with a diode surprised me, makes me wonder how they get 1123nm that way. I will continue researching this, I have the YAG, or what sure appears can be nothing other than a YAG, so want to start dreaming of a build for it.

Edit: I have very little information on how this was used, except the photo of the unit being side pumped, don't know if there might have been a thin crystal between the diode or not yet but I can't imagine that being done, since the output is yellow and not green. Is there such a thing as a 1123nm diode? I have never heard of one. I have tried contacting these companies in the past and made the mistake of letting them know I was a hobbyist, always crickets when I do that. Perhaps a different approach will work.

Click to expand...

Well, you can side-pump pretty much anything if you hit it hard enough, it just might not have very decent beam quality. AFAIK almost all commercial CW 561nm is 808nm diode -> 1123nm Nd:YAG -> 561nm NLO crystal. There is probably some exotic dopant for some exotic crystal that can produce similar wavelengths, but I'm assuming we're staying practical here. Also, why do you think there may be a thin crystal between the diode and the crystal? Honestly curious.

Also possibly of interest: Diode-side-pumped 1123 nm Nd:YAG ceramic laser

EDIT: ALSO possibly of interest: Not a half-bad price on brand-new rocks designed specifically for 1123 and 561: Nd:YAG 2x2x5mm, 1123 nm, 561.5nm

Re: 561nm Yellow YAG (?) from Lumens Varia Eye Laser

I don't think there is a crystal between the diode array and the YAG, I see no evidence of it, just responding to a post by 94Z28 asking about the possibility of multiple crystals. If there were such, they only way there could be one is if it were a thin sheet, or adhered to the pump diode array facet.

Re: 561nm Yellow YAG (?) from Lumens Varia Eye Laser

Alaskan said:

I don't think there is a crystal between the diode array and the YAG, I see no evidence of it, just responding to a post by 94Z28 asking about the possibility of multiple crystals. If there were such, they only way there could be one is if it were a thin sheet, or adhered to the pump diode array facet.

Click to expand...

Ah. I see what you're saying. My bad.

Do you know what kind of NLO crystal this particular laser uses? Or any ideas on the resonator configuration? From the picture, it looks like there's a mirror directly behind the YAG, so probably not a ring laser.

Re: 561nm Yellow YAG (?) from Lumens Varia Eye Laser

It would be side pumped by 808nm .

Its works the same way another other DPSS system dose , instead the YAG is side pumped and it will then lase at 1123nm due to cavity coatings , then its converted to 561nm by a SHG crystal .

Re: 561nm Yellow YAG (?) from Lumens Varia Eye Laser

Don't know anything more about this yet, all I have are the photographs I received from the seller. I do however have a photo showing most of the full unit:



I can't yet tell if the YAG has coatings on it or not, it is being sent to my home in Alaska while I'm in Baghdad.

Edit: I have to laugh now, NOW I see the "561" marked on the module to the far middle right in this photograph where the SHG crystal must be, I had thought the diode (but what had me confused is I didn't believe a 1123nm laser diode existed) was pumping the crystal with 1123nm which was itself a NL crystal which converted to 561nm, wrong... I was confused because while I was wondering if that was how it worked, I also saw the mirrors like a YAG would use.

Mystery solved, this is a ND YAG made for side pumping with 808nm. Perhaps with coatings for the 808nm diode but probably with mirrors which are HR for 1123 and suppress 1064nm, just like a flash lamp YAG would have for 1123 shooting into a non-linear crystal for doubling the frequency/halving the wavelength to 561nm yellow. I also happen to have a crystal made for doubling 1122 to 561 which should take the power to produce a half watt of yellow

Second Harmonic 561nm LBO Laser Crystal, YAG : Nd 1122nm Lithium Triborate | eBay

Thank you guys, I'm happy for anything else I can learn about this thing if you want to share more of your thoughts. I didn't know 808nm could be used to excite a ND:YAG to produce 1122nm, when using a flash lamp with a regular ND YAG I had thought there was a component of the flash energy at close to 1123nm which a ND YAG would use to amplify the light, if the correct mirrors were used, but perhaps that isn't correct (???), I've looked at the wavelength profile for the energy produced by flash lamps made for ND YAG's and much of the energy is closer to 808nm, so is that what is happening with those?

Re: 561nm Yellow YAG (?) from Lumens Varia Eye Laser

Alaskan said:

Don't know anything more about this yet, all I have are the photographs I received from the seller. I do however have a photo showing most of the full unit:

I can't yet tell if the YAG has coatings on it or not, it is being sent to my home in Alaska while I'm in Baghdad.

Edit: I have to laugh now, NOW I see the "561" marked on the module to the far middle right in this photograph where the SHG crystal must be, I had thought the diode (but what had me confused is I didn't believe a 1123nm laser diode existed) was pumping the crystal with 1123nm which was itself a NL crystal which converted to 561nm, wrong... I was confused because while I was wondering if that was how it worked, I also saw the mirrors like a YAG would use.

Mystery solved, this is a ND YAG made for side pumping with 808nm. Perhaps with coatings for the 808nm diode but probably with mirrors which are HR for 1123 and suppress 1064nm, just like a flash lamp YAG would have for 1123 shooting into a non-linear crystal for doubling the frequency/halving the wavelength to 561nm yellow. I also happen to have a crystal made for doubling 1122 to 561 which should take the power to produce a half watt of yellow

Second Harmonic 561nm LBO Laser Crystal, YAG : Nd 1122nm Lithium Triborate | eBay

Thank you guys, I'm happy for anything else I can learn about this thing if you want to share more of your thoughts. I didn't know 808nm could be used to excite a ND:YAG to produce 1122nm, when using a flash lamp with a regular ND YAG I had thought there was a component of the flash energy at close to 1123nm which a ND YAG would use to amplify the light, if the correct mirrors were used, but perhaps that isn't correct (???), I've looked at the wavelength profile for the energy produced by flash lamps made for ND YAG's and much of the energy is closer to 808nm, so is that what is happening with those?

Click to expand...

I highly doubt the YAG itself has anything other than AR coatings on it. It even looks like there's a HR mirror to the left of it in your initial photo, though it's difficult to figure out the entire resonator design without a better photo.

As for pumping, 808nm can excite all of the common transitions (946, 1064, 1123, 1319, etc.), which is why you'll sometimes see people getting weak red or green out of their 589nm Spartans, even though it only uses one crystal as the gain medium. I believe 869nm can pump Nd:YAG as well, but it's much less common.

You're going to need some rather expensive optics to get this thing lasing, and IIRC 1123nm is one of the faintest commonly used lines. So I wish you luck in getting it working! :beer:

Thank you again, all of this information is great, like a fountain of cool water in a hot desert. I agree, it might be awhile until I can get the parts, but I did find this OC mirror a few minutes ago:

Yellow Laser OC Output Coupler for Diode Laser 200mm Brand New Nice | eBay - From the listing, this OC mirror appears to have a 200mm and from that, I believe this must be a resonator mirror with some kind of focal length, but looking at the photo's, the mirror appears planar or flat, so I am not sure about that.

Edit Add: It says OC mirror for yellow laser, I'm betting it is the OC for the 1123nm line of a ND YAG, the same seller I got the YAG from. Probably the same mirror used with this YAG. I ask questions of him, but he doesn't seem to know more about anything he sells than what he puts in the listings. If that is what this is, then all I need to find to complete the optical resonator is the 1123 HR mirror for the back side of the YAG, correct? My assumption is both mirrors need to be "tuned" to that line/wavelength, correct?

Alaskan said:

Thank you again, all of this information is great, like a fountain of cool water in a hot desert. I agree, it might be awhile until I can get the parts, but I did find this OC mirror a few minutes ago:

Yellow Laser OC Output Coupler for Diode Laser 200mm Brand New Nice | eBay - From the listing, this OC mirror appears to have a 200mm and from that, I believe this must be a resonator mirror with some kind of focal length, but looking at the photo's, the mirror appears planar or flat, so I am not sure about that.

Edit Add: It says OC mirror for yellow laser, I'm betting it is the OC for the 1123nm line of a ND YAG, the same seller I got the YAG from. Probably the same mirror used with this YAG. I ask questions of him, but he doesn't seem to know more about anything he sells than what he puts in the listings. If that is what this is, then all I need to find to complete the optical resonator is the 1123 HR mirror for the back side of the YAG, correct? My assumption is both mirrors need to be "tuned" to that line/wavelength, correct?

Click to expand...

Sorry to get back to you so late, that is a great price for a 561nm optic though (or any optic mind you).

But depending on what you want out it may or may not be what you need. It depends on whether the 1123nm is doubled intra-cavity or extra-cavity (inside the 1123nm cavity or outside), assuming it is indeed the OC from the same laser the YAG is from. If the 1123nm is doubled intra-cavity, (which is very likely, but due to the low gain of the 1123nm line possibly not.) then it will likely be HR 1123nm and HT (or AR) 561nm. If it is doubled extra-cavity, then it will probably just be PR 1123nm, so it all boils down to whether you want 561nm light or 1123nm light.

If you have a higher quality version of the photo of the resonator I/another member could probably figure out the resonator design and tell you which it is (intra or extra).

As for the "200mm", they could be referring to either the focal length or the RoC, which would be twice the focal length. And just throwing a HR onto the back might work in theory, but in practice you'll probably want to build at least an L/V-fold cavity if you plan on building a 561nm to keep the 561nm light out of the YAG, and also so that you can get a higher energy density in the KTP or whatever NL crystal you're using.

Also, have you ever built a solid-state laser before? If not I wouldn't recommend starting with 1123nm/561nm until you've got a firm grasp on aligning mirrors, phase-matching crystals, and just building 1064nm/532nm units overall. I know that this can be an expensive endeavor, but it's a good investment.

I'd also really appreciate UK and/or any other vets with solid-state laser knowledge to give their $0.02 if you're reading this.

OK, much food for thought, thank you again.

I've been studying the optical path and components of the Lumenis Varia photograph and believe I see what is going on now, this must be the L/V fold cavity you were writing about; the silver box marked 561 on the far right I had earlier thought was the NL crystal is perhaps a filter to remove 1122nm and instead the crystal located in the copper mount shown in the lower left side of the photograph, within the red eclipse. From this, the doubling crystal appears to indeed be inside the YAG's optical cavity.



Nope, never built any kind of DPSS before but I can do it, here is a story showing why I think I can do what the inexperienced usually cannot pull off:

I wanted to build a 5000+ watt output 144 MHz linear power amplifier in the past and when doing research before hand, consulted the head engineer at Eimac who told me my project was too difficult for someone to just throw something together like that without following a RF engineers design, that without being an engineer it would never work right without spending a long time working out the wrinkles, if ever.. He was wrong, I studied RF amps for a year before I started and my project worked first time I powered it up and the only changes I later made was to increase the thickness of a Teflon insulator between a tuning cap and ground. What he didn't know was I would study and plan for a long time before beginning. I don't have a EE degree, but I am now an RF engineer in my current job. I built that 20 years ago, I see this project the same way, just needs a lot of study before hand. (maybe last famous words from me, lol).

I do not have a photo of the 561nm (so called yellow/lime green) section showing the NL crystal, but here is a close up of the 532nm green KTP (copper/left side) section:



One of the things I am wondering about a small YAG like this, is if a Q-Switch can be used with it so the unit has enough punch to poke a hole in an aluminum gum wrapper. I was hoping a physical chopper might work to Q-Switch, if not that, a passive Q-switch glass, or perhaps AOM.

Sounds like you've got most of it down pat. I wasn't trying to discourage you, if you think you're up to the task then by all means go for it. I was just trying to illustrate the complexity of such a project. It's like jumping into a basketball game without having practiced all season. It's definitely possible, but it's certainly not easy.

As for Q-switches, if I were you I would avoid physical chopper to minimize vibrations and cavity disturbances, and they typically don't give very short pulse lengths anyway. SA Q-switching is a very viable option, and is actually what I would recommend for your first time (no extra electronics + easy to install/uninstall), but it's very doubtful you'll get very high pulse energies using one. SA/passive Q-switching is typically used when fast repetition rates are desired, rather than high power. AOM and EOM Q-switches are used for high peak powers, so if you want to do anything even remotely destructive with your laser, you'll want to use one of those. You could possibly even make your own EOM with a homegrown KDP crystal and some polarizing elements if you're up for it. Something else to keep in mind is that it probably won't be easy to find a SA or AOM/EOM designed for 1123nm for any less than your first-born child and the deed to your house, and because the line is so faint you'll want to minimize any losses you can.

But before you delve into Q-switching, you should probably just get the laser operating first.

Here's some further reading on the subject. I assume you've read/understand most of it already, but there might be something new that you haven't seen:

https://www.rp-photonics.com/q_switching.html
https://www.rp-photonics.com/q_switched_lasers.html
https://www.rp-photonics.com/resonator_design.html?s=ak
https://en.wikipedia.org/wiki/Optical_cavity
https://www.rp-photonics.com/phase_matching.html?s=ak
https://www.rp-photonics.com/frequency_doubling.html
https://en.wikipedia.org/wiki/Second-harmonic_generation
https://www.rp-photonics.com/saturable_absorbers.html?s=ak
https://www.rp-photonics.com/acousto_optic_modulators.html?s=ak
https://www.rp-photonics.com/electro_optic_modulators.html?s=ak

Ah, every time I ask someone who knows how hard it can be for someone new to DPSS, especially something like this project, they warn me of the possible difficulties and for good reason, I will probably tackle easier projects before I move on to this one, so will be studying for awhile before I would start this, maybe over a year more.

Good news, I was able to get a copy of the manufactures drawing for this unit:





Thank you very much for the links, they are very helpful.

Chris