Cleaning and re-aligning a DPSS labby

[Blarg King]

Hello!

My B&W Tek 473 labby isn't outputing very much, less even then its 10 mW rating. I've read that cleaning and re-aligning them is the best way to improve them, but I haven't been able to find instructions on how to do so.

So, does anybody know how to clean and re-align DPSS lab lasers? How difficult is it?

 

[Sigurthr]

I've realigned several of these units. My best was getting 73mW output stable.

YOU NEED 808nm AND 980nm protection. NO EXCEPTIONS. There are many, many mW of IR reflections inside the head, most of which pointing right up into onlooking eyes.

It is damned near impossible to realign these units with them off, just ask Bloomie (least I think it was him).

The heads are hygroscopic, so time spent with the lid off has to be minimized, and room dehumidification will help a lot.

The basic process is simple; remove the lid, remove the plastic casing shell over the NLO MCA assembly. This single NLO MCA unit will be the ONLY submodule you will adjust. Do not attempt to adjust the diode mount or any of the anamorphic prism optics unless you have reason to believe they have been moved. These heads do not allow for much if any adjustment of the NLO MCA in the vertical axis, so it will mostly be XY translations and planar rotations. Simply loosen the screws holding down the NLO MCA, but do not remove them, now move the assembly in a methodical manner to find the best output. Lock it down once there.

Since these heads are hermetically sealed, it is unlikely there will be any cleaning needed inside the head. Thermal cycling usually precipitates the need for alignment though.

 

[Blarg King]

Okay. I can set up a small room with a dehumidifier to work in. Gotta get myself some IR glasses first.

EDIT: Thermal Cycling? Does that mean let the laser warm up and stabilize first?

 

[Sigurthr]

Temperature cycling - Wikipedia, the free encyclopedia

It's what happens when the laser is turned on and allowed to warm up, then turned off. Effects are cumulative.

 

[crazyspaz]

I have a small 532 CNI labby that I have realigned a few times (mainly for the heck of it), and what I have found best is to barely unscrew the screws holding the component in question (in this case, the LBO assembly), and then using a screwdriver, leverage it against the case and gently push the component at the base. This allows for very gentle, fine movement, and when you have it where you want it, you can tighten the screws just a tiny bit and its all good to go. If you loosen the screws too much, sometimes the component will shift when you are tightening them back down (especially if you take all the screws all the way out- don't do that).

 

[ultimatekaiser]

this is a complex question. best is to determine why it's outputting so little. is it mode hopping? does it have a tem00 dot? is it round or an ellipse? what power are you getting out? is the output clean? has it been tampered with? (opened before?) these are all questions you need to ask yourself first. I can walk you through it bit by bit if you like. its not too hard to realign an already existing cavity.

edit: and btw crazy's advice is spot on. minimal movements are best. loosen screws only as much as you need to be able to nudge them around and move stuff, then tighten back down gently and not too firmly. this minimizes walk-off of parts as you tighten them down. but bear in mind the looser you leave things, the less thermal conductivity and the faster it will naturally lose alignment from thermal cycling. the parts you need to move will be based on the questions i asked before.

 

[Blarg King]

it mode hops as it warms up, but once it reaches a stable temperature its got a nice clean round dot. I don't know how much power I'm getting because my LPM won't even register it, hence my wanting to improve it. I've never opened it before, and thought its been owned by others before me, the "warrenty void if removed" stickers are still intact.

A step by step walkthrough would be most helpful if your willing. I would love it if I could get this laser working in peak condition.

 

[ultimatekaiser]

I can sure do that. And if you have Skype with a cam or something, I can even walk you through it real time. But first you need some IR protection for 808 and 946nm. Preferrably OD 5 or higher.

 

[Blarg King]

Hmm would the survival laser OD 5 ones be good? Only other decent ones I can find are the laserglow ones and though they're OD 7 they are also really expensive.

 

[ultimatekaiser]

they're probably fine. the lab tested ones at laserglow are awesome though. I have a similar pair but from a different company. they're used for YAG alignment, which is why they're so expensive. they have to resist really powerful pulses of light.

 

[TheGreaterWatt]

I am dealing with the same problem myself. I had my B&W Tek in storage and the mount for the crystal assembly broke free of it's thermal paste and now I am having a hell of a time getting it to lase again.

I cannot really tell if I am just terrible at aligning the darn thing, or the seal was bad and I am just wasting my time.

 

[ultimatekaiser]

I'll offer to fix it if you guys just want to send them my way with their power supply and driver.

 

[Blarg King]

Nah I'll give it a try myself.

 

[TheGreaterWatt]

I will give it a week to start laseing again... If not I may send it out for professional help.

By the way, when running the tec gets really, really cold. And starts to gather condensation I am assuming this is bad for the moisture sensitive LBO, but does it effect the lasting properties of the crystals?

 

[ultimatekaiser]

Sounds like the driver is set incorrectly.