frequency doubling...

[Conceptcar3]

I noticed that this site offers 50mW 980nm diodes for $13 a piece (minimum order 1000 unfortunately!) But what I am wondering is, I am aware that 473nm blue is created by using the same KTP crystal as a green laser, with a 946nm IR diode. IF we used this 980nm 50mW diode with a KTP crystal, would it frequency double to ~ 490nm producing a blue-ish turquoise laser, or is that not possible? Obviously it would be a pretty weak laser if that would even work, and we would need a lotttt of people for a group buy haha. Let me know why this doesn't work, b/c I feel like KTP wont frequency double 980nm. At the same time, why will it with 946nm?

http://www.diytrade.com/directory/g..._Manufacturers-980nm_50mw_IR_laser_diode.html

 

[Aseras]

the problem is efficiency and that certain crystals only lase at very specifc wavelengths. ktp has a couple of resonance lines, so you can lase at diffrent wavelengths but it's very very inefficient. ktp is usually used in cheaper low end blues, BBO & LIBO crystals are much more efficient.

 

[Conceptcar3]

yea I figured it would be inefficient... but we could use BBO instead.... do you think that would work to produce 490nm light though? If we can even get 10% efficiency (5mW) I'd be happy!

 

[Aseras]

it's not that easy, firstly you'd need a 200+mw pump diode for even 5mw.. or less. most of the blue handhelds, like the rpl blue are 2.5 watt pump diodes.. for 25mw. blue is incredibly inefficient. it's not worth it right now unless you absolutly have to have it. you'll spend more sourcing the parts than if you just bought one.

blue direct injected diodes will be out by the end of this year, and the dpss blues are gonna go the way of the dodo.

 

[Conceptcar3]

hhaha sweet, thanks for the help

 

[SenKat]

Aseras - are you sure that the rpl blue uses a 2.5watt pump diode ? I do not doubt your word - but that seems horribly inefficient, and I do not think the crystal would only put out that low amount of blue with that amount of pump diode...it just doesn't sound right to me !


Conceptcar - I have a few 980nm diodes here that I can try that with - I DO have other projects going right now, but remind me in about a week, so I can give that a shot, okay ? I also have a few TEC's sitting here, to coll the crystals with if that becomes an issue - maybe a possibility for a WEAK labby ? We'll see what happens - will be fun to mess with and try at any rate :naughty:

 

[The_LED_Museum]

DPSS blue lasers *ARE* horribly inefficient. :shakehead:
2,500mW pump diode for 25mW blue output = 1% conversion efficiency. :green:

In a 473nm blue DPSS laser, there's a BIG infrared laser diode that generates laser light at 808nm, this is fired into a crystal called Nd:YVO4 (containing neodymium yttrium vanadium oxide) that lases at 946nm; this laser radiation is finally fired into a crystal called LBO (containing lanthanum boron oxide) that doubles the frequency to 473nm - the bright blue color you see.

Green lasers are doubling the 1064nm transition of Nd:YAG or Nd:YVO4, or some other similar host medium. The 946nm line is what is being doubled in blue lasers, and 473nm light is the result. Often, the choice for a Non-Linear Optical (NLO) crystal is different for the two lines. KTP is the crystal of choice normally for green, and LBO for blue. Also, the 946nm line has a much smaller cross section for emission. This means lower efficiency and the 1064nm line and even the weak 1319nm line will try to compete with it, stealing energy. On top of that, the 946nm line is self absorbing making the device a lot trickier to generate (like ruby, this is a case where the laser medium is actually somewhat opaque to the frequency of light the laser is trying to operate at, where as YAG is almost perfectly transparent at 1064nm).