Laserscope collimation (or lack thereof)

[Laser Ben]

http://www.ppsfx.com/html/fiber.html

[dsli_jon]

Hey Nic -

Hi Jon,

That's an unconventional prism arrangement... what's it do?

...'UP-PERISCOPE!!!' Bascially, it is a 'home-brew' periscope to deal with the beam-height disparity between the on-deck fx / galvo-level MM1s, and the fiber input-coupler we used on this particular-build - it is a 'retroreflecting' prism, used by LS to steer the 1064nm on the OEM medical-deck, but 2x, butted-together (and one flips-around) you get a very nice, nearly-lossless periscope...(don't let that 'huge glow' in that one pic 'fool-you', there is zero 532-leak thru the 'top-face'...)

..Like I said, the 'raw-medical-deck' of these things is like a 'free trip to the candy-shop'... (not to mention, at-least ~$50. or-so worth of quality cap-, pan-, and countersink-head screws...)

This can also be used 'sideways' for beam-steering, but works 'better' vertically, cause they can just 'sit' on top of one-another (albeit, epoxied on the sides, for 'security'...) - sideways, you'd have to rig-up more to keep the faces perfectly 'mated'...

Here's another 'trick' (see pix-below) using the 'real' periscope that LS uses down-the-line, (to 'engage' the beam into the final fiber-delivery IC)... it makes for a nearly ideal 'beam-shifter', up-deck for on-deck galvos... Used in-conjunction with the 'OEM' stepper-controlled polarizing-stage, you can actually use this to both 'control' power-output (via pass-thru / reflection by polarization-rotation, just like they do it...) and be the 'metering' point for a 'real-time' power-meter...

So, when can you schedule-me-in to come 'down-under' and help you convert this thing?

I would really like to learn how to terminate the fibers, I have read a lot about it before and I would like to have a go. Previously I thought the reflection would be too high without AR coated ends, but I am prepared to try it.

Could you give me any clues about the 200um fiber and SMA connectors you use? I can't seem to find 200um fiber at Edmund.

Well, #1, scratch Edmunds ...IMO, they are only 'good' for a few lenses / acromats and the 'CDAR' super-high-AR glass windows, (which - btw, is THE BEST, IMHO, for making aperture / projector-windows for these things - when you are dealing with 40+ WATTS, <0.5% back-reflection vs ~10% for 'standard' glass, becomes REAL IMPORTANT!!! - everything-else Edmunds sells is pretty-rediculously over-priced / marked-up...

...So, yeah, (Thanks, Ben! ) PPS sells component-level kits, and so-does 'OSLS' - and they will prolly be a bit-more 'wallet-friendly'.. we use PPS fibers for WL / non-Q-Sw'd 532 apps, and OSLS' fibers for KTP- always had good results.... And, while I 'pat you on the back' for wanting-to learn how to cleave / polish / make your own fibers, , I do feel obligated to '411-you' to be-prepared to drop a good $2K + on all the 'stuff' - fiber-cleavers / finishing kits are not 'cheap'... 'Word to the wise'...

A small side-note (from PPS' site / fiber-specs) about '30W down-a-fiber', that is for CW-ONLY (ie, a giant Argon, etc) it is NOT recommended to pump more-than 20W MAX down a 200µm fiber, Q-Sw'd, because of the MUCH-higher 'peaks' of 532 in those pulses... best to do like, 20W, 50/50'd into 2- 10W launchers, and then *try* for 8-9W for SL/SR remote heads... PLENTY of power...(see shot below w/ 4x ~8W heads and 2- 4W beam-table units, SL/SR...) If you want to truly-use +20W, you will need to go bigger (400µm - 600µm) - then, of course, up-goes the beam-diam. / divergence...

Pat / Steve - (couple of my favorite-mentors... ) feel-free to jump-in anytime, and augment / correct my 'advice', here...

ciao for now...
j

[Laser Ben]

A small side-note (from PPS' site / fiber-specs) about '30W down-a-fiber', that is for CW-ONLY (ie, a giant Argon, etc) it is NOT recommended to pump more-than 20W MAX down a 200µm fiber, Q-Sw'd, because of the MUCH-higher 'peaks' of 532 in those pulses... best to do like, 20W, 50/50'd into 2- 10W launchers, and then *try* for 8-9W for SL/SR remote heads...

Very good point about the q-switching. I didn't even think about that! Do you guys have any use for the medical fibers that are used with the laserscope system? I know a guy around here who has nearly a thousand of them.

[LesioQ]

And how's the Laserscope 600 dye att. pumped by q-sw 532nm via fiber ? Is it some large core / huge face spot attitude ? I thought these were designed for up to full 40W 532nm pumping, right ?
Piotr.K

[LesioQ]

Still as I mentioned earlier I think (claim ?) that if z-fold's 20cm r.o.c. mirror was allowed to pass green, we would be able to get far better beam specs for lasershow use.

532nm beam spot on this mirror is about twice smaller than on OC (50cm r.o.c.), so with additional optics right here the final spot could be smaller.

I'm considering trying to replace this 20cm r.o.c. HR@1.06/HR@532nm mirror with 15cm r.o.c.HR@1.06/AR@532nm to check this thesis, but this change may require shortening the relay optics distance. This would also change the relay factor from 2.5 up to 3.3

Anyone ?

Piotr.K

[mixedgas]

run the cavity model in PSST! ?

http://www.st-andrews.ac.uk/~psst/

note lens duct in psst = rod. :-)


Steve

[dsli_jon]

Hey Ben -

Do you guys have any use for the medical fibers that are used with the laserscope system?

Nah, thanks... got a few for 'experimentation's-sake' and no real need for show-use... thanks anyway...

I know a guy around here who has nearly a thousand of them.

Wow - he could make QUITE a cool lit-up 'Millennium Falcon' model with that!! (I tried that as a teen, after seeing a 'special' on 'the making of Star Wars, and man, it reeeeally 'works' for making little 'window lights' in a model... very-cool...)

Hey Piotr-

And how's the Laserscope 600 dye att. pumped by q-sw 532nm via fiber ? Is it some large core / huge face spot attitude ? I thought these were designed for up to full 40W 532nm pumping, right ?

Well, if I understand what you are asking, correctly, the 600 Series Dye was designed (according to 'specs') to-be pumped with exactly (probably +/- a percent or two..) 16W of 532, to-give the 'spec' 3W of 630nm (for its 'particular treatment-purposes) - which can 'shift' power-output depending on what wavelength the grating is 'tuned for'. While the fiber that comes 'standard' with the unit, I believe is a 400µm, I am sure you *could* pump MORE into it, with a 6 or 800µm fiber. ie: I pumped ~20W into ours, and saw ~5W peak... it was niiiiice...

The point I was making to Nic was that you don't wanna pump a 200µm fiber with more-than 20W, cause with such a 'relatively tiny' fiber-end vs such high-peaks as-are found in any Q-Sw'd beam, you stand a greater chance of 'burning' the end - not so-much of the FIBER, but of the TIP - focused-down to that tiny spot, even 20W's (+ 'spikes') IS DEFINITELY ENOUGH to 'burn' a fiber-tip - the 'power density' is MONSTER at that point... So, yes, you CAN pump more into fiber - it just has to be correspondingly-bigger fiber...

Take THIS beast, for example - boasts - no, MEASURES 80 Watts - OUT of the fiber!!! Read the listing: "... On Laserscope's test sheet (prior to shipping the system), the technician measured 110 Watts of 532 nm at 53 Amps..." Holy schnikey, that's a lotta green!!! Not exactly-sure, but I am pretty-sure that uses at-LEAST 800µm fiber, with that much power...

As-to how this relates to the Dye sys - well, yeah, with bigger fiber, you *can* pump more into the dye-cell, and because the dye-beam is a separate 'lasing-process', the dye-beam-quality is the result-of the dye-cavity optics, NOT the 532 pump-beam... In fact, I'd bet you could just rig one of these dye heads up-to a 532-deck (maybe an over-under config) and DIRECT-pump it (lose the fiber, and you'd also have-to do a little minor optics-rework in the dye head...) with 30+ Watts, and see 8-10W of Red!!...Imagine that...10W of 629nm!!!

The only 'limiting-factor' then-becomes dye-cooling / power-handling / efficiency, and keeping the dye-cel window 'clean' (cause any dust or 'funk' that floated into the beam would 'burn' on the window very quickly, and thus, take power down drastically...) Worse, if some 'funk' got inside, and the burn happened inside the dye-cel, than you'd have to take it apart (read: drain it..ugh) and clean.. of course you 'could' also 'shift' the dye-cel 'up' to a 'new', clean part of the dye-cel window.... But I am getting off-track, here...

Nic - again, if you get a 'kit' from either 'PPS' OR 'OSLS', you mostly need to make-sure you tell-them it is 'destined for-use with Q-Sw'd KTP' - there are different-spec fibers (even at same diameters) for-use with Ions vs KTP... (really, it is non-pulsed vs pulsed...) They do things like cleave the fibers at a 'slight angle' (vs 90˚) to minimize back-reflection, down the optical-train (PS - Thanks to Steve Roberts for that little gem of info...

Anyhoo, ciao for now...
j

[Laser Ben]

Yeah, there are a lot of Laserscope parts around here. Unfortunately, most of them end up in the hands of people who think selling a used part at 90% of the new cost is a great deal.

[dave]

Just for interests sake, has anyone done a conversion to a greenlight?

Take THIS beast, for example - boasts - no, MEASURES 80 Watts - OUT of the fiber!!! Read the listing: "... On Laserscope's test sheet (prior to shipping the system), the technician measured 110 Watts of 532 nm at 53 Amps..." Holy schnikey, that's a lotta green!!! Not exactly-sure, but I am pretty-sure that uses at-LEAST 800µm fiber, with that much power...

j

[Laser Ben]

I think it is a relativly new system so I doubt anyone had done something to the model. 80W CW is quite impressive! I love the look of that fiber.