Cheapest way to a big greenie ;)

[smogthemog]

No nose jokes please

What is the cheapest way of me aquiring a 1W+ Green laser diode?

Would it be to purchase a high power 808 and stuff a KTP in front of it?
If so, would any KTP that will lase green when exited with 808 do?

I have a spare set of 15K scanners sat here and need a project for them.

Thanks
Jim

[andy_con]

theft!! !

[stanwax]

Jim if your understanding of how a green laser works involves thinking that KTP is being excited by 808nm then you really should not be considering making a green laser yourself just yet.

First of all the 808nm pump diode excites ND atoms in a host material, which in the case of most small DPSS is Vanadate (can be YAG, Glass or others) When excited at sufficient levels the ND will lase at 1064nm (there are others that make blue red and yellow but lets not complicate things here) - you need a cavity for this to happen. The 1064nm is then reflected within the cavity so it passes as many times as possible through a Second harmonic generator - the KTP. To explain simply, this creates harmonic distorsion on SOME of the 1064 passing through it (hence the need to pass it back as many times as poss) This distortion manifests itself as light at a frequency of double the original and so half the wavelength 1064/2 =532 greeeeeen.

You will need - High power 808nm diode, Vanadate xtal, ktp xtal, output coupler with suitable coatings, beam shaping optics for the pump light and output beam, tec temp control of the assy as a whole at min but ideally of each of the diode and the 2 xtals. and you will need to mount them securely in a fashion that will allow the temp control to work, align and position all these bits accurately - being sure they wont move at all in use.

Its reasonably easy to knock up the bits you need to make a DPSS laser make green light (in small quanitities) - however to do it at any level of effeciency and a reasonably high power - which 1 watt is to be considered for these purposes need good accurate machining of parts, good selection of the laser components, as well as excellent alignment and temp management. Its within the realm of the hobbyist but it will take up lots of time and in the long run probaly cost you more than just buying one.

Not wanting to put a downer on your idea or anything

Rob

[smogthemog]

I think I will stick to me Jet engines at present

Way out of my league there Rob - I will forget that one at the moment and save up to buy one. If I lived on me own, had no ankle snapper and suffered from insomnia then I would perhaps give it a go BUT none of the above is unfortunately applicable at the present time.

Ok, so what your saying is there is a lot more to take into consideration and what I was suggesting is ok for tiny pointers and thats about it.

Again Rob, thanks for the information. I will skulk off now and read a book on lasers - problem - suffer badly from ADD so that's out of the darn question!

Thanks matey

[smogthemog]

theft!! !

LOL - Just seen your post Andy after replying to Robs

[smogthemog]

Question still stands - what is the cheapest option please?
I am thinking single LD or 10x 100mw Pointers and a series of PBS's?

I am guessing the pointers would be cheaper?

[stanwax]

You can only combine 2 lasers with one cube once per colour per installation
more cubes will not work.
Rob

[smogthemog]

I don't quite understand Rob?
How did P1tbull (Steve) do it with all those reds? I thought they where multiple LD's combined using multiple PBS's.
1 PBS combining two LD then 2 of the same combined using a further PBS, so on and so forth?

[buffo]

No. The things that look like PBS cubes in his projector are actually mirror mounts. You can only use a PBS cube to combine a pair of beams *once*. The reason is that the output beam from a cube is randomly polarized. If you send the combined beam into another cube, you'll loose half the beam. (Same thing with the other beam you send in.)

The way to combine multiple diodes is to "stack" the beams very close together using the knife edge mirror technique. Essentially you send one beam *very* close to the edge of a mirror, so that it just misses it, and then aim another beam at that mirror edge so that when it reflects off the mirror, it's parallel with the first beam. Now you have a pair of beams that are *very* close together.

Do this for a pair of lasers that emit horizontally polarized beams, and also for a pair of lasers that emit vertically polarized beams. Then combine the two pair of beams using a PBS, and you get a resulting output that is (roughly) 4X the power of 1 diode.

The problem is that the beam profile of your output will be TEM 01. Nothing you can do about that though. (Some people have stacked many, many diodes together to create a very multi-mode beam - think TEM 34 - and then used expensive collimating optics to try to clean up the beam.) You're going to end up with a fatter beam using the stacking technique, but it is one way to get higher power out of ordinary diodes.

Adam

[smogthemog]

Excellent Adam, Totally understand now, thanks for the information.
I think the way to go is a group buy the next time one come up bearing such gifts.

The 1W Vaisho's seemed a very good option as looking at various website prices, they where darn cheap!

Thanks again.

Jim