Anyone have info on the Lumenis Novus Spectra?

[Alaskan]

Has anyone seen one of these for themselves, or know of anyone who was able to get one of them running? It is either a Lumenis Novus Spectra, or a HGM Elite Ophthalmic 532 nm green 808 nm bar pumped YAG-KTP DPSS laser, but not sure which one of the two. Wondering what the max power out they can safely produce. As a guess, I'm thinking their rated output is likely half of the possible.

Lumenis Novus Spectra

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Sales page, some info: http://www.globaldsr.com/equipment/surgical/surgical-lasers/photocoagulation-lasers/lumenis/lumenis-novus-spectra



More pics: https://imageevent.com/qdf_files/te...communications/dpsslasers/lumenisnovusspectra

 

[LSRFAQ]

Yeah, I have a friend who services those. I've been in the room when he works on them. They are horribly multimode by design, to ensure a uniform light pattern out of the medical fiber onto the target. . They have the divergence of a flashlight, expect to have to collimate. Designed for about 30 seconds to one minute of duty followed by a cooldown. If you run them CW you get a lot of power for about one minute and then they become horribly unstable, and your missing what you need to close the light loop.

Eye Surgeons and Dermatologists use their lasers for short periods of pulsing, followed by a cooldown, so the above statement is within design parameters.

The pump diode is an array of about 50 diodes across a centimeter or so bar. Diode Idne (Do not exceed) is about 20-21 amps. So start with low currents, monitor the output with a known good LPM. The design puts vast amounts of pump power into a tiny, tiny, passively cooled rod, and you are missing the massive heat sink that module sets on..

The AR coatings on the end of the TINY rod are incredibly soft, I'm really good at cleaning rods, I get paid to do it and have the correct materials. I damaged that coating on one of many Ebay rods I have bought for the other nefarious wavelengths. So clean with care, if you dare.... I'm redesigning the rod holder cooling for a reason, as I need a gentle CW beam at lower powers.

Pump diode is point blank into the rod, that rod gets hot and the beam blooms. Note there is no Indium pad on the rod, so if you overtighten the rod holder screws, the rod cracks instantly. I imagine Indium would quickly melt in this design.


Requests for a copy of the schematic have been promptly ignored by my friend and for good reason. It's his livelihood, and generally those in the medical laser business do not like the risk of untrained amateurs working on medical systems. He has helped in the past with other schematics, pump current levels etc,. The Lumenis data was a NO, period. I've asked for others before.

There is a YouTube movie some place by a PLer showing the beam after he hooked it up to a diode driver and slowly ramped up the current.

Lumenis was the result of Coherent and I believe Sharplan buying HGM.


Steve

 

[Alaskan]

Thank you Steve,

I wanted this as a test bed to use with other crystals, not sure that is a wise idea, have no idea how difficult they are to get working, once changing something even a slight amount I might find myself in trouble, don't know, have never touched the inside of a DPSS system before. Maybe I should just count myself fortunate if I can get it running at all without doing anything more with it. I realize heat sinking is going to be the first order of business. I don't have a clue what size of heat sink was used with it, anything you can tell me about the heat sink? All of the TEC's are intact.

Any idea of how much power I might get out of one of these when pushed hard, but not so hard as to damage it, if running for one minute or less?

Now that I have you here for a moment, here's my other baby, if you know this one too, any comments on possible amounts of power output for any of the three wavelengths?

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[LSRFAQ]

Yes, the Yellow is 600 mW long pulse, rated as delivered to the patient. The red is 659 nm @ 600 mW max Delivered. The Green is 532, 50 mW to 1.5 watts delivered. Pulse times were 0.05 to 3 seconds. Hence my warning about low duty cycle being a design function on the green laser.

I have a few of the EBAY yellow rods I'm starting to use, but I am not using Lumentis optics, for other reasons I can't discuss openly.

Steve

 

[LSRFAQ]

BTW, see that intracavity wavelength filter on the yellow? Pro Tip, there are weak Nd:YAG lines close (a few nanometers) to 1123 that will lase at very low energy, but will suppress the more powerful 1123. For example, 1121 nm. Don't change the filter tuning, as the filters are angle tuned. If you slip the filter(s) out, 1064 with its massive gain will lase and kill most if not all lasing at 1121 and 1358, resulting in, no red, and no yellow. So the optics there are specially coated to kill 1064 and possibly other lines, except in the green laser.

Steve

 

[paul1598419]

I didn't see a 1319nm pass filter, so you are saying it is only the HR and OC coatings that suppress the 1064 line in the red laser?

 

[LSRFAQ]

Yes, the 13xx lines have about 1/3rd the gain of 1064 where as 1121 has about 1/6th. That and the fact that the extra 100 nm gives the coating designer some wiggle room.

I know a gentleman who was wealthy enough to have custom mirrors made for an 800 series KTP 532.. 15 watts of 659 was a sight to behold in the days before high power diode arrays. He still had to have his coatings >60% transmission at 1064, as do I on my little 1121 nm mirrors.

Alaskan, remember, Idne on all three pump diode arrays is 20 amps for 30 seconds until you can get hard data. The ktp ovens are easy, just slowly warm them up till you see peak R Y or G with a current limited power supply.

Diode based med sleds go for about two years without a Planned Maintaining visit (PM) by an FSE. Odds are the Varia RYG Is still aligned and good to go if no one messed with it. Yearly PMs are preferred for nearly all medical systemsm but that does not mean the cavity will drift much,
Steve

 

[Alaskan]

Steve, you are the first person I've found who can tell me much about these, appreciate your help. I looked on PL for that video, didn't find it, but just ran across this video of the Novus Spectra being fired up by YT swissrocketman:

Lumenis Novus Spectra

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Do you know why the 532 nm green doesn't go strait out of the end of the assembly and is redirected to another output using the additional optics? I see three pieces beyond the OC.

If you have any extra rods or parts and pieces to make yellow you ever want to sell, please PM me.

 

[paul1598419]

I have to agree. This thread has turned out to be quite informative. Thanks, Steve. You made me think in ways I never would have without your direction.

 

[LSRFAQ]

Alaskan,

Two fold mirrors are used to precisely set height and exit direction so all units are interchangeable in the field. A collimator lens to set all diameters equal from unit to unit between the mirrors, and I would not be surprised if there is a waveplate inside the collimator to prevent back reflection from disrupting lasing.

The last mirror is also one of multiple beam pickoffs in the medical system, ensuring patient safety. From the glimpse I was given of similar medical system schematics, there is an SCR across the diode power supply as well as mechanical shutters to prevent a patient overexposure controlled by two independent circuits that watch pulse intensity and pulse width.

If I ever have yellow parts to spare you'll be the first to know.

Steve

 

[LSRFAQ]

Be aware that there are 10 or more lines that can lase in the ND F manifold, I checked a friend's ancient green Nd:YAG based pointer the other day and found 1084 lasing with 1064. Be aware that 1064 has a weak sister line about .2 nm away from the primary 1064. In YAG 1064 has about 1,1 nm of gain bandwidth, so you often do not see just a narrow spike on the optical spectrum analyzer but the whole "Twin Peaks" + neighboring line ND:YAG spectrum. There was even a touch of 543 from the KTP faintly doubling the 1084 line, but incredibly faint and I needed a spectrometer to see it.

Not all ND:YAG lines lase in all crystal hosts, for example ND:YLF lases at 1047 and 1053, but which line lases depends on how the crystal is oriented to a polarizer or Brewster plate in the cavity. This is because YLF is birefringent. YLF does not lase at 1064 nor 946. So this gives you 523.5 or 526,5 nm greens.






Steve
[/QUOTE]

 

[paul1598419]

I have two very cheap green pointers that are Nd:YVO4/KTP based and have multiples lines. One has 4 lines and the other an amazing 6 full lines of green. That is why I was testing all the same type pointers with my spectrometer to see if I could find more of them. The 6 line one has to run for a bit before all six lines appear. I found one which would climb in wavelength over time. Not a lot, but enough to see that it was happening. When I reported finding this I was insulted for not knowing what I was doing because I was told this was not possible.

 

[Alaskan]

Steve, much appreciated, saving this thread as a pdf. Good to know about the lines, someday I will get a spectrometer, right now, you, Paul and I believe Cyparagon are the only members who have one. If you are willing to spend a bit more time helping me with more, I have a few more basic questions I have been searching for the answers to:

I have recently found a source of uncoated 3 mm x 12 mm long ND:YVO4 crystals I've been pondering upon whether I can use them uncoated without much problem to shoot 808 nm into to produce 1064 nm, or for that matter, as a gain medium itself to produce 1342 or 1320 nm without AR coatings?

Also, can you tell me if these two statements are correct?

1. The angle the NL material is cut from the crystal determines the wavelength you can SHG from it, the angle it is cut for locking in the pump wavelength to be used for SHG with that crystal.

2. Rotation of the crystal in its holder is merely for peaking the efficiency of the SHG conversion alone. Different rotational angles in the holder do not alter the pump wavelength the crystal itself is most efficient at (for a particular cut).

If I have understood DPSS correctly, the wavelengths I can SHG using a crystal I find on ebay are not only limited by the AR coatings, but also due to the physical cut at the time of manufacture.

Edit: I had more questions posted here earlier, but edited them out, I don't want to run you off as I could probably load you with far more than you would want to deal with, at least, without being paid for it, if you even had the time.

 

[LSRFAQ]

OK,

Now before every one gets happy, and hundreds of LPFers senselessly download the software, and start fantasizing about potential new laser wavelengths just because the software will calculate a crystal, forget about it, in the real world it does not work that way.

You still need to design a cavity, calculate gains and losses, check if the crystal has thermal issues, and solve several quadratic equations to find the interaction length etc.. Just because you know the rough cut angle for a piece of KTP does not mean you'll suddenly be able to single pass frequency double a diode laser, or have mixture products, OPOs etc. There is quite a bit more to it then that, like selecting proper polarizations for Type I or Type II Shg etc...

Just because you know the angle and can buy a doubler of some random length, does not mean you can make a laser. Because no two batches of KTP or most of the other crystals ever perfectly match the Sellmeier Coefficients Database in the software. SNLO gives you a place to start, but you need more data on the actual batch of crystal before you can buy.

OK, That said... questions: 1 yes, sorta. 2. No. We can tune crystals using angle, temperature, or in some cases external electrical field. I used to work on lasers that used rotational tuning of multiple crystals that were held at a constant high temperature to avoid grey tracking.

SO Alaskan, Download SNLO free version from AS Photonics..

SNLO (free version) - AS-Photonics

SNLO classic (free version) Buy this book and get the most out of SNLO! SNLO is widely-used, cost-free software developed by Dr. Arlee Smith. It is a native Windows application, with several functions to assist in selecting a nonlinear crystal and modeling its performance. It includes data for...

www.as-photonics.com

Click on Qmix, and in RED 1 and RED 2 put in 1064.1, select KTP, convert 80'C to Kelvin, put in the temperature and click run.. It will give you an estimate of Phi and Theta and tell you some interesting things about what you might get, including the "blue" box displaying 532...

Steve

 

[Alaskan]

OK, so I was kinda on the correct track, appreciate the refinements. I downloaded the program, but need install a Windows emulator on my Apple notebook to run it.

One good thing about using parts from my Lumenis Novus Varia to build a pointer, all of the crystals and optics as well as dimensions already there, I expect it might not be possible to make a stable pointer with those parts, perhaps unable to make an unstable one either, but one of my units had all of the TEC's and heatsinks stripped off of the bottom of it, so no harm tearing that one apart, but I was hoping for more power at 561 nm than 600 mw long pulse.

Edit: I understand a "pointer" won't be possible with those optics in a standard configuration, will have to be a fairly large triangle shaped cavity and unconventional heat sinking to even try. Not sure I can get it to work at all without TEC's either and with them, short lived operation. I expect a lot of issues, but want to see what can be done.

 

[LSRFAQ]

You cannot change the cavity dimensions. The mirrors are placed to put a beam waist inside the cavity at the doubling crystal in order to ensure enough power density inside the crystal to enable doubling. When they design the cavity they want the beam volume to fill the YAG rod as well. There is no practical way to change it to a linear cavity, the V shape is carefully chosen to correct for astigmatism in the internal optics.

Remove the optics from the base plate, have a shop CNC the base into the triangles, seal it up very, very, well as intracavity dust will kill it, and call it a day. Water cooled yellow pointer. There are common drivers that will run off 24V, so now your talking 24 volt marine lead acid on a backpack for power. If you do try to make a linear cavity out of it, you'll get a fraction of the yellow at best, I'd be shocked if you saw 75 mW for any length of time.

Steve