473nm vs 589nm vs 532nm

[zazman69]

Just wondering, if green, yellow, and sky blue lasers all use the same type of device to create the color, why are sky blue and yellow lasers so much more expensive than green lasers? i understand the basics of how it works, just hoping that a more experienced member might point me in the right direction from here. :yh:

 

[StardustSprinkles]

They are all Diode Pumped Solid State lasers, meaning a diode fires laser light through crystals to achieve the desired wavelength. The main reason for the higher price of yellow and blue DPSS lasers is how hard it is to make the crystals required, they make lots, but can only use a few, so they charge you their loss.

 

[zazman69]

I see now thank you very much. Also, would you prefer to use an Nd:YAG or an Nd:YVO4? i know that the YVO4s are cheaper but are they as good as the classic Nd:YAG? :thanks:

 

[ZRaffleticket]

They use the same crystals, just different wavelengths these operate in.

The three crystal (Nd:YAG) wavelengths used in these process are 946nm, 1064nm, and 1318nm. these specific wavelengths must only exit the crystal, so you need to apply a coating (number one to force the crystal to produce only it, number two to prevent your "pump" wavelength from leaking.) These coatings aren't as efficient as eachother and some of these wavelengths aren't as strong as the other.

532nm comes from a very strong frequency doubled 1064nm wavelength, with a very easy to produce coating and isn't that hard to align.

473nm uses a rather weak wavelength and a different coating, 946nm frequency doubled (wavelength halfed). Since it's a weak wavelength you can't produce as efficiently, less power, and the coating isn't easy to come by. Alignment isn't too easy on these either.

589nm uses a special type of DPSS, which is called SFG (Sum Frequency Generation). Basically, it combines two wavelengths the crystal produces, and frequency doubles the average. (formula=1/((1/WL1)+(1/WL2))) This method is EXTREMELY inefficient, EXTREMELY hard to align, and the coating is EXTREMELY hard to produce.

Hope I shed better light on the matter!

 

[Cyparagon]

YAG is better (more efficient) for high power or pulsed operation while YVO4 is better for low or medium power. There are some wavelengths that only show up in one or the other, too. I think 473 requires YAG and will not work with YVO4. 473 also uses a different doubler - usually LBO instead of KTP if memory serves

 

[zazman69]

thanks very much everyone. Does anyone know where I can buy an Nd:YAG crystal? Im trying to duplicate this experiment for some friends: Homemade 532nm Green Laser - YouTube

 

[ZRaffleticket]

Confirming cyparagon's post, Nd:YVO4 cannot produce 473nm. 473nm also doesn't use KTP but it's either LBO or BBO... I think LBO is more efficient.

edit: check this thread click

 

[Roam]

1064 nm is the most commonly used transition in YAG and YVO4 BUT you can get other lines too. For example from YVO4, one at 914 nm which then generates blue light at 457 nm (if you use LBO).

You can pump Nd:YVO4 with 808 nm to get that 1.064 μm (the 473 nm lasers use 808 nm diodes as the pump too). Then you need an intracavity frequency-doubling crystal to make the 532 nm.

Incidentally you can use the resulting 532 nm to pump yet another crystal Ti:Sapphire (Ti: Al2O3).

You can use lithium-triborate (LBO) for green lasers too just like KTP, they both double the frequency producing light at λ0/2=532. I think the main difference is that LBO is less susceptible to optical damage.

 

[zazman69]

^wow, very detailed and thurough :worthy: . thanks very much! :thanks: but i have to ask..... where did you learn this? virtually everything i know about lasers has come from an online document or a youtube video. That is why i came here :yh: Im planning on ordering some IR diodes and some YAG crystals. where can i get them good and cheap? (i dont need help for the diodes)

 

[Roam]

You are welcome, hope that helps. I did a course on laser physics once and that's about it but I got the chance to play around a bit with a few nonlinear crystals (that make different multiples of the wavelength), heterodyning different beams and observing their beat notes, etc.

As where to buy the crystals from... I know that Meredith Instruments sells YAG slabs and waffers, as well as YVO4s. At one time they even sold Ruby on ebay (Sapphire crystal doped with Chromium).

But as I said before, you will also need a nonlinear crystal to double the frequency of your fundamental light (1.06 μm IR from your Nd:YAG laser) and generate the second harmonic (green light at 530 nm). For this upwards conversion you will need crystals like KTP, KDP, LBO... (it turns out that Ge- and P-doped silica-glass fiber also does the trick). You can buy KTP at different dimensions also from MI. This might be the most suitable crystal for your project and is not that expensive there.