Seeking advice on using the parts out of a Half-Note 532nm laser to build a pointer

[Alaskan]

Hello,

I'm looking for advice regarding the use of the parts out of a Half-Note 532nm medical laser to build a high powered pointer. Perhaps heat and temperature management of the diode as well as the KTP will be impossible for 2 watts of power and this project shouldn't be undertaken, or the alignment of optics too much of a problem without experience? That's pretty much what I'm guessing but wanted some second and third+ opinions.

Here's a photo of what is under the hood:

Does anyone know if it is really necessary for the IR to zig zag all over the place after HR2, if not, whether I can place most of the optics in a less spread out configuration better lending for pointer use? Is a round trip through the KTP crystal assembly really necessary (if a IR filter is used down stream instead)? Any idea on where the 1064 conversion is taking place, perhaps inside the metal & crystal KTP assembly? What does OC mean, is that where the conversion to 1064 takes place somehow, if so, what's going on there?

Thanks for your time reading this and helping, if you can.

 

[TheGreaterWatt]

Does anyone know if it is really necessary for the IR to zig zag all over the place after HR2, if not, whether I can place most of the optics in a less spread out configuration better lending for pointer use?

You can slim down the cavity, to a linear one by leaving out all the other HRs. Having one behind the YAG then the OC after the KTP.

Simple diagram:

HR---YAG---KTP---OC

Is a round trip through the KTP crystal assembly really necessary (if a IR filter is used down stream instead)?

Yes, see below...

Any idea on where the 1064 conversion is taking place, perhaps inside the metal & crystal KTP assembly? What does OC mean, is that where the conversion to 1064 takes place somehow, if so, what's going on there?

In essance the diode bar causes the YAG crystal to emit 1064nm light which is doubled by the KTP to make 532nm light. The mirrors direct the 1064 light into the KTP to be doubled and the doubled light only escapes through the OC (optical coupler)

If you are thinking about going through with this project, it may be worth it to read up on the basic DPSS theory. Check out Sam's laser FAQ, or browse around here. (I would link you there but it is a pain on my phone)

This could be done, not easily mind you, but it is possible. Turning a z-fold cavity into a linear one is not an easy task, and it might very well be cheaper to buy parts specifically designed for such a purpose.

Also if I remember correctly, that diode bar needs something like 10 or 20 amps to make 2 watts of green.

 

[Alaskan]

TheGreaterWatt

Thank you, I had a weak link in regards to pumped YAG's, didn't know they could produce 1064 from 808nm, thought it was a coherent amplification cavity alone when pumped with a specific frequency instead of a relatively broadband flash tube. Now I'm trying to determine through online searches if the rod is made out of yttrium vanadate.

If I were to convert this into a linear laser and used the same optics in the HR---YAG---KTP---OC configuration, my understanding is that I would need to use the same distances between components as were used in the Z fold configuration in order for the focal lengths to work out properly (except the KTP placement distance away from the YAG isn't critical), is this correct? This would make a rather long assembly, is that the only advantage a Z fold gives, to make the unit more compact?

What concerns do you have for the difficulties I might encounter requiring the purchase of new parts?

You are correct about the drive current required, the 808nm diode max current is 25 amps. I also have a PDF giving some information on the unit, but not much on the cavity except the quote below: http://photos.imageevent.com/qdf_fi...tions/irledandlaserproject/Lightwave DPSS.pdf

Laser Cavity
The Laser Cavity is hermetically sealed to prevent contamination. It contains the YAG rod, Photocells, Diode, and Mirrors. The YAG rod is side pumped by a diode array. The current controlled diode array controls the output power. The IR beam resonates between the mirrors and the doubling crystal. As the IR passes through the temperature-controlled crystal, the second harmonic is filtered out and passed through a Green Output coupler and IR high reflector...

Edit: I just found thus diagram in the PDF manual, I overlooked it the last time through. I believe this unit needs collimation to produce a infinite focus beam. When I tested it for output, the size of the spot on the wall was fairly large, appeared to be expanding quite a bit which is fine, I can let it expand a lot and then add a large diameter PCX lens so the divergence is reduced. I'm not into burning things or a small diameter beam, prefer ultra low divergence instead.

 

[TheGreaterWatt]

Now I'm trying to determine through online searches if the rod is made out of yttrium vanadate.

It is very likely the YAG is just YAG as it has better properties, if I recall.

If I were to convert this into a linear laser and used the same optics in the HR---YAG---KTP---OC configuration, my understanding is that I would need to use the same distances between components as were used in the Z fold configuration in order for the focal lengths to work out properly (except the KTP placement distance away from the YAG isn't critical), is this correct? This would make a rather long assembly, is that the only advantage a Z fold gives, to make the unit more compact?

I would suggest you start reading here: Sam's Laser FAQ - Solid State Lasers
Or,
Sam's Laser FAQ - Home-Built Diode Pumped Solid State (DPSS) Laser

In theory you could just use HR4 and the OC for a linear cavity, the beam might have some weird modes and have a decrease in power due to incorrect focal length, but it should lase.

What concerns do you have for the difficulties I might encounter requiring the purchase of new parts?

Well new parts, like mirrors and diodes will undoubtedly be expensive. They are available but expensive.

Honestly if you wanted to build a pointer you would have an easier time buying a hybrid crystal set and a smaller diode. The pointer would end up being smaller and you wouldn't have to would about providing power for that side-pumping diode bar. Also thinking about things like temp control, which is critical if you want power over 1W, it will be extremely difficult to fit all that in a handheld.

 

[ultimatekaiser]

Can't see the picture in the OP...

What are the dimensions of the crystals? What's the actual output power of your half note?

 

[The Lightning Stalker]

When I tested it for output, the size of the spot on the wall was fairly large, appeared to be expanding quite a bit which is fine, I can let it expand a lot and then add a large diameter PCX lens so the divergence is reduced.

All SHG/THG are like that. The divergence
will be bad because the beam is so small.
It needs a beam expander.

 

[Alaskan]

Thanks, I've been eager to see more comment on this. Here's a photo of the KTP crystal assembly, it is a metallic enclosure with a hole in it, very small, you can see it sandwiched in between two glass blocks with a small TEC (warmer) in this photo:

That's my index finger on top, so you can see, it isn't very big but puts out 2.3 watts.

 

[ultimatekaiser]

Looks like a nice hydrothermal grown 3x3x5. Pretty standard for that much power. And that is very big actually, compared to the cni made 2x2x10 or 2x2x15 flux grown lower quality cni ones. Looks like a fancy corrected L fold they got going in there.