Viasho 1W 532nm with fault, only 400mW stable output

[weartronics]

Hi Folks, I have a Viasho 1W 532nm which was operating normally, but the power output has dropped to 400mW. I suspect there is a fault with the diode, the KTP, or the alignment (but the head has never been opened to look). I think the driver module and the power supply are both fine. I already bought a new system to replace this one in my projector. I know a few of you guys have experience repairing these, in which case this one's going pretty cheaply!

www.ebay.com.au/itm/151016764530

Regards, weartronics

[gottaluvlasers]

LOL- its a Viasho. They *ALL* have or will have faults!!

[weartronics]

LOL- its a Viasho. They *ALL* have or will have faults!!

Thanks for taking the time to post that here. I'm sure the CNI modules you sell will last forever.

[gottaluvlasers]

No, they probably won't. However, my comment was fitting for the thread from my experience with them. Not too sure what got your panties in a bunch.

[Bradfo69]

I have exactly the same problem with my 1 watt Viasho 532. It's right at 400mW. I can't say that I've ever heard anything particularly good about Viasho - seems they all have problems. Supposedly a nice beam but epic failure rates. Perhaps not as bad as Las(n)ever but, in following threads the past few years, I'd personally be more than a bit hesitant to ever spend a lot of money on one. (Not knocking your eBay listing. Hell...I may even bid. Probably a pump diode and alignment issue but very few can do it from what I've found out when trying to get mine fixed.)

[weartronics]

Yep, it seems to be a fairly common failure mode. This one was removed from my Kvant Spectrum projector (Kvant uses Viasho for their 532nm modules). I'm not game to open up the laser head, so I just bought a replacement (same brand, same model, because it's a pretty close fit inside the projector). But I know that Shrad and others are handy at repairing/realigning them and have been asking around here for parts in the past, which is why I posted this one. Regards, weartronics

[White-Light]

Don't know how old your Kvant is, but I think Kvant now use cni for their greens.

[dave]

Yeah, the green in yours is a CNI OEM-H IIRC

[shrad]

for info, these are V-fold and are NOT trivial to align

I'm still trying to get some stable green... the first thing to do if you have one and it is bad enough for a global realignment is to replace ALL screws (like if they were in lead or something... a pinch and they are unscrewable)

After that, you have to carefully measure pump power at a given current... then you place the YVO4 and measure power again, and align for maximum absorption

This is what I know about it and have assumed from myself

Once done, you place the OC and HR... the OC when aligned in a linear fashion will extinct fluorescence in the YVO4 as gain will occur at the fundamental (you see a faint yellow light in the YVO4, and it disappears when aligned)

When aligning the OC to the HR to fold the cavity, you will point from the YVO4 to the HR and see "the little red dot" walk its way to the HR on a small piece of anodized ally like a fan fin (CAUTION do that at less than 100mW of measured 808nm pump and caution, you need to be sure there is no harmful reflections to you eyes !!!! do NOT look at it from front, always from the side)

When you face the HR at the good angle, the fluorescence extinction will occur again at cavity alignment (the "red dot" should output at the middle of the HR)

Before this step you have to set the distance from YVO4 to pump at the point of minimal "red dot" intensity, in fact this is where I told to get maximum absorption at the LPM

You may have to tweak distances to get maximum extinction of the fluorescence

Once that done, place the KTP and align to the eye in the good axe... then power it up at the 100mW pump stated above, check for green light, and once found you can then put some good goggles and start pushing power to tweak everything a bit

This can be tedious as you can have a good green level at low power to find out that it fades later, as this is not the sweet spot.... you are good to start again to a previous point (depending on what you did to find more green)

This is my method, knowing that I know how to get a look at a working pump from the side with an IR viewer or a black cardboard or metal (reflections etc...) and I'm used to IR lasers due to previous work (VERDI, MIRA and MILLENIA)... as soon as th pump exceeds 100mW or so I put some OD7 on my nose


If people like Pat or Steve were able to comment or tell anyone some advices to do things better or in a safer way, please tell as it would benefit everyone here... I'm not a guru and I want to learn and share, so it would be a nice idea to complement what can be found online like on Sam's FAQ which is a bit unadapted in this field (except basic safety and holding, I'm speaking more about things like V-fold alignment etc..)

[weartronics]

Hi shrad, What you describe sounds like a fairly conventional alignment procedure for any YVO4/KTP laser. Though of course the V-fold arrangement has the disadvantage that the beam moves a lot when the KTP is installed, making the alignment is more iterative than usual. But I agree this procedure is non-trivial, requiring detailed knowledge of the system and fairly specialised experience. Thanks for bringing all your alignment tricks here, because yes, Sam's FAQ is a bit lacking in specific techniques.

In an unrelated 100mW 532nm Viasho head I owned, the screws were made of cheese (where they were present at all), but they were only used for the factory alignment - all the optics were glued down so that the alignment could not change (and could not easily be realigned after e.g. replacing the pump diode). Once you have broken the glue to move the optics, you really need temporary adjustable mounts to align them before gluing again. Poking the loose elements around with a stick gets very tedious very quickly... Except for a very small group of people, this is one case where there really are "no user servicable parts inside". I converted that head to 1W 442nm using one of the first Casio diodes ($550!) instead - a much simpler proposition!