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Coherent Genesis 577nm Laser (FINALLY)

ultimatekaiser

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OK OK OK! I get it. You guys want to see this. I know I've been promising it for ages. I know I've been away....I kinda was out of the laser vibe for a while. Money has been short lately and I've not been able to work up the motivation to really do any major reviews and posts and such for a long time, so I'm sorry for my absence. I'm finally getting off my ass for a little bit (so to speak) to get into the OPSLs that people are always me asking about. For those who don't know, OPSLs are greatly superior in a number of ways to crystal based solutions, due to their ease of variance (wavelength) and scaling (linear power increase) and due to the fact that the OPS chip that creates the fundamental wavelength being not very picky about its' input wavelength like Nd3+:YAG is and being so very thin, green noise and power instabilities are very very low. Stability can be made quite phenomenal by comparison without tons of extra work in many cases. These lasers are essentially similar to the Coherent Sapphire, just more powerful, and built vertically instead of horizontally on a ceramic plate. They consist of a custom made type of 808 ish diode bar, which is corrected and focused onto the OPS chip which then emits as a VECSL of sorts, which is then run through a BRF hits the OC and then is doubled between the OC and an HR on the upper deck. The BRF and doubler are of course temperature controlled to control the wavelength (frequency) and doubling efficiency, as well as keeping the cavity under control. This results in a very compact and well contained laser setup that is very stable. the base of the diode is also the case however so this means the case of the laser is diode + which can present some problems however as most supplies are - ground! This means that the heatsink is isolated from the laser and the general solution is to float the laser on a pair of TECs. this helps maintain the diode/case temperature stability, while cooling the laser and keeping it isolated all in one go. The laser is then held on by bars that screw into the heatsink. the bars are wrapped in kapton tape to insulate the head at the point of contact. The TECs it sits on are massive. each being 12V at 8A wired in series. So after applying thermal compound and setting it up, it was time to fire it up!

Let me note that I happened to get these by sheer luck and the fact that I just so happened to find these at a fairly reasonable price (relatively speaking) and knew sources for the equipment to run them. They're quite complex to run and require quite alot of fancy electronics. The power supply is quite large and made up of many different very high cost parts. It's quite large and luggable, consisting of of a main supply, several tec drivers, a diode supply, and several other bits and bobs, as well as a coherent driver, all crammed into a box in a very tidy and elegant way...but holy heck would I not want to have to take this thing apart. The driver has some parts bridged on, and it's clear that it was from the early days of these lasers (2007-ish) back when these were still in a preliminary phase. The newer ones are digital. The unit I have is one of several that coherent made as an example demo supply for these lasers as far as I know, and despite its analog nature, still works great and tanks along just fine despite being pretty huge.


Everything you'd expect is here. CDRH key, readouts for current and power output, modulation, a knob, and indicators. you can also switch back and forth between constant current, and constant power control. Although I have noticed that you should stop the laser before switching between modes otherwise damage may occur as the current control knob is not limited by the set max current! so if you switch from power to current mode and back bad things can happen resulting in instant death of the laser potentially as it can result in a massive current spike. YIKES! There are a few trim pots inside that are fairly well labelled and makes tuning this laser fairly easy despite needing some patience and understanding of how they work.

I actually have a few of these. Two 577s, of which one works, the other I had to replace a few parts in, and have not yet had time to realign, but it is now complete again. and I have a green one that had a diode mishap, and has since been replaced and is now chugging away happily as well. You can see them side by side here.


The 577 is quite gorgeous. It is virtually impossible to catch correctly on camera however, but it is indeed a nice lemon yellow, and seeing it in several watts of quantity is quite breathtaking, however the downside is I can't really run it at such a power without extreme precautions in place as it burns holes in virtually everything it touches very very fast even for a multimode laser. I would take it outside and shoot it into the sky, but as there are several airports in the area, I'd very much hate to end up risking harm or distractions to anyone up there, let alone attract any neighboring attention so I've not done that. There is a fair amount of splash light due to the insane power involved so taking pictures is quite a challenge. The 577nm module runs smoothly, emitting a fair bit over it's 3W rating at its' rated 30A of current, and producing well over 4W at its' maximum recommended current of a whopping 36A! It can technically run higher, but doing so would likely be to the detriment of the diode and will be left as current headroom for the unit as intended. I generally run it at very low powers anyway however, as anything more than about 50mW is blinding anyway. Power stability for the laser is incredibly good, generally within a milliwatt or so as far as I generally see in the short term, which is quite amazing. In the long term I've not really watched closely but it seems to not really drift at all. The massive factory heatsink setup is quite overkill but it certainly works very well. The huge 12V fan on the back sounds like a jet engine taking off on top of the power supply. But enough chatter. I'll shut up and let you enjoy what I know you all came for!

Head at Idle:

Laser spot on the wall at idle:

Beamshots!

https://imgur.com/pkL85xa

https://imgur.com/u1wAzV7


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ultimatekaiser

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<Reserved Post>

Note that the beamshots are at generally around half a watt to a watt of power, the only full-power-ish one is the one from behind shooting into the Ophir sensor, as it is the only thing I had at the time that I took these that can withstand the power without damage, so I floated it just below 3W since that's what the sensor is rated up to. Maybe sometime I'll take more at a higher power when I come up with a good beam dump.

Also, I apologize if all the pics don't show. Evidently it's a forum limit of 5 media per post.
 
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BowtieGuy

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Wow, UK, that's a beauty, ....and a beast! Thanks for sharing this unique (to us) wavelength. :cool: (y)
It looks like all but two of the pics show up great, the other two work with just a click on the link.

I've got to imagine that if you leave this running for very long, you'd see it in your electric bill. :ROFLMAO:
 

Encap

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Awesome super quality laser ---3W to 4W of 577nm---rare bird---very nice.
Not many get a chance to own a high quality Coherent made laser and have to settle for a Chinese also ran due to cost constraints.
Enjoy it.

Great addition to your impressive collection of lasers.
 
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paul1598419

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Thanks, Matt. I have been waiting for you to review this laser for a long time. I see you photo-shopped the beam shots as cameras won't pick up the color correctly and it comes out looking green. Great review, buddy. It was worth the wait. :D
 

ultimatekaiser

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Wow, UK, that's a beauty, ....and a beast! Thanks for sharing this unique (to us) wavelength. :cool:(y)
It looks like all but two of the pics show up great, the other two work with just a click on the link.

I've got to imagine that if you leave this running for very long, you'd see it in your electric bill. :ROFLMAO:
Definitely alot more than your typical DPSS, but not a ton. Probably in the neighborhood of 100W. The diode is 1.8V or so at 30A at spec, plus the TECs would be 24V because they're in series, and typically run at an amp or two iirc. The little ones in the head are very small and probably are measured in milliamps. probably 1V at a few hundred mA. More than a little handheld or something for sure, but not outrageous. Still far less than a CVL or a huge 3W watercooled Ion laser. Heck of a lot smaller too.


Thanks, Matt. I have been waiting for you to review this laser for a long time. I see you photo-shopped the beam shots as cameras won't pick up the color correctly and it comes out looking green. Great review, buddy. It was worth the wait. :D
Actually I didn't shop them at all. They came out that color. Although it's still more yellow than in the pics. But this camera is pretty decent at getting the color compared to most others I've tried. I almost did a video review, but that'd take quite a while., and I'd need to get a tripod. But nothing short of seeing it in person does it justice.
 

paul1598419

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I should have remembered that, as it looked quite yellow the first time I saw it on a Skype conversation with you. Mine is just a few nms lower in wavelength than yours, but it comes out very green. As I recall, yours looks more green at high powers on the camera.
 

ultimatekaiser

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Yeah and to be honest depending on the lighting in the room sometimes it can look somewhat greenish at first glance too. But as you turn the power up it looks more and more yellow. The yellow spectrum and orange spectrum are really strange because they’re so small.

The units are surprisingly heavy for how small they are. They’ve got quite the weight to them. They’re made out of a very thick very high-quality machined Aluminium frame. You can tell that no expense was spared. Optics are soldered in mounts, and mounts are then screwed into the framework, the main deck is held in six different locations the cover held on by six alternating-pattern/staggered screws with washers and all the screws or torqued to a very specific amount to reduce frame stress as much as possible...there is also a O2absorber and desiccant inside on the roof in them to protect the doubler, Mirrors are truncated on the corners to keep things from chipping and bumping together, There’s a rubber seal between the lid and base...electrical connections are made by insulated push pins connections...The list goes on and on. Just the machining alone probably cost a significant amount. This is not a cheap laser, by any stretch of the imagination.
 
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paul1598419

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Huh. I didn't know the frequency doubler is hygroscopic. Which crystal does it use? I know these are very expensive. I am very envious of you. :)
 

RedCowboy

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Neat piece of equipment and a cool laser beam. (y)
I do see a hint of green in the yellow beam on my screen for what that's worth.
I hope we see some direct yellows soon. :)
 

ultimatekaiser

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Yeah there’s an oxygen and a moisture absorber inside. I’m pretty sure it’s an LBO or similar iirc. Likely chosen due to the high damage threshold and low cost. Opening one of these up for the first time it feels like a trying to pry open a vacuum seal. Not that I would ever encourage anyone to ever do that. It’s definitely not what I would call “user serviceable“ the Sapphire is the same way. They are very likely assembled by a special robot or human assisted jig of some kind. Working on these by hand as a royal pain.
 

paul1598419

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I doubt it is lithium triborate because that crystal is not hygroscopic. I have no idea what it might be, though. I would be interested in finding out, however.
 

ultimatekaiser

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I’m pretty sure that it is an LBO. It’s cheap in flexible and has a high damage threshold with low birefringence, making it a good choice. In the original preliminary documentation I think that’s what it said they used, but I’d have to check.

Edit: and yes LBO is mildly hygroscopic.
 
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paul1598419

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If it does use Lithium triborate then the desiccant you have in the lid is for something else. I don't know what else it could be there for, though, as there isn't really anything else that could be hygroscopic.
 

ultimatekaiser

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It has an oxygen absorber in it. see above, I'm guessing you missed that. The result is it makes a low pressure system in the head so trying to open one is a bit of a pain, as it sucks itself shut.

Edit: and yes it is an LBO according to the preliminary documentation I have from wayyyy back when. Though that is for solely the green WL so that isn't necessarily conclusive, but I'd be inclined to believe that it is the same for all of them, just cut slightly differently for the different wavelengths.
 
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