Frequency doubling crystal question

[Greenhorn]

Just a quick question - frequency doubling crystal sets are only for specific wavelengths, right? I wouldn't be able to shine a red laser through the set for a green pointer?

 

[ElektroFreak]

Yes. Nonlinear (doubling, tripling, summing, etc.) crystals are only usable across a certain range of frequencies depending on the crystal in question.

 

[Hemlock_Mike]

If you double a 660 red, you get 330 nM --- Don't go there. Also the doubling crystal needs "mirrors" plated on each end to establish the resonance.

Mike

 

[suiraM]

Last I saw, SHG doesn't technically need mirrors, although it will certainly be very inefficient to omit them.

A greenie crystal is a different beast, since it isn't just a SHG crystal, but also a lasing crystal, with three coatings in there that are essentially dichro types. That makes it virtually useless for any other purpose. You could always try to use it from the other end (hence preserving the orientation), at a very tight angle (to avoid the dichro coating), at some specific temperature, in which case there might be a few wavelengths you could reach. Effectively, though, the rig to do so will probably cost more than acquiring a better SHG crystal that is easier to orient.

As you say, though, doubling anything that's shorter than 808nm is a no-no for hobbyist purposes.

Methinks a 20W bar, doubled to 808nm, would make some people violet with envy, though.

P.S.: I forgot you again, Mike. I will remedy that.

 

[Laser_Ben]

Yes, a few watts of 808nm light would be nice. However, directly doubling a diode is very difficult. Check my thread in this section about the Coherent 430. That is one of the only directly doubled beam ever to be produced by a company. Mine was 10mW and cost $50k.

 

[suiraM]

-nods-

Although I meant to say "double to 404nm," your point is still quite valid.

I thought the efficiency was somewhat higher, though.

Thanks for clearing up that misconception.

 

[diachi]

Why is it a no no I always wondered what would happen if I reversed the crystals in a green laser.

Your crystals will glow a pretty green colour :

 

[Greenhorn]

Is there a way to directly double the frequency of a 808nm diode? It would be pretty cool if I could get a 1W or bigger 808nm diode and double it, and have a superbright violet laser. I don't know anything about doubling crystals, but wouldn't doubling 808nm just involve using the same crystals as a 1064nm, but slightly different orientation or something?

 

[Laser_Ben]

To answer your questions...

Is there a way to directly double the frequency of a 808nm diode?

Yes, not for you or anyone on this forum though...

It would be pretty cool if I could get a 1W or bigger 808nm diode and double it, and have a superbright violet laser.

While it would be really cool to defy physics and everything, it is not possible for all practical reasons... The 10mW 430nm directly doubled laser I have uses a 4W 860nm diode. It also cost $50,000 new.

I don't know anything about doubling crystals, but wouldn't doubling 808nm just involve using the same crystals as a 1064nm, but slightly different orientation or something?

No, you would need a completely different medium. Orientation would have a lot to do with efficiency, but this isn't even close to getting to that part...