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# Could someone help me out on this.

##### New member
So just yesterday I contacted dragon lasers about their handheld yellow pointers, I asked about how they worked. Things such as pump wavelength and processes used. Shortly after I checked gmail to find a nice letter from Adam explaining that the yellows used a 808nm pump. He did not know the exact process but I decided I could probably figure it out.

Here is how I imagine it works,

I realized that Nd: YAG emits like this,

so perhaps a Cr: YAG would work better,

I kind of doubt that though and either way both crystals are incredibly hard to get a hold of to emit at their 1180nm lines.

So is this possible? Im not thinking of building this anytime soon but i'm curious if this is how they make yellow handhelds.

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#### diachi

##### Well-known member
You're making some incorrect assumptions. Those emission graphs for one tell you nothing about which wavelengths those crystals will lase on. You can't just pick any wavelength under the graph.

Yellow pointers use Sum Frequency Generation not Second Harmonic Generation/Frequency Doubling. The process is essentially the same but the big difference is that SFG uses two different input wavelengths. For 589nm the Nd:YAG is lasing on 1064nm and 1319nm. For 593.5nm they use Nd:YVO4 which lases at 1064nm and 1342nm.

The equation for calculating the sum frequency result is the same as the equation for calculating the difference frequency result, except you swap the "-" for a "+".

Difference frequency generation equation:

If you plug 1064nm into the sum frequency generation equation for both λ1 and λ2 you'll notice that you get 532nm out.

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#### paul1598419

##### Well-known member
Yes, that is a great explanation of how to get 589nm through SFG. The end equation is correct with the minus sign replaced with a plus sign. The proof of that equation is much more complex, though. Nice job, diachi. + rep.

#### diachi

##### Well-known member
Yes, that is a great explanation of how to get 589nm through SFG. The end equation is correct with the minus sign replaced with a plus sign. The proof of that equation is much more complex, though. Nice job, diachi. + rep.

Cheers! :beer:

I really need to edit that image for SFG or find another one, but explaining it does the job.

#### RedCowboy

##### Well-known member
LPF Site Supporter
Don't you need a input and OC mirror and the crystals optically bonded?

#### diachi

##### Well-known member
Don't you need a input and OC mirror and the crystals optically bonded?

Yes, you need a HR and an OC with the appropriate coatings, doesn't necessarily need to be using a bonded xtal set though. I'm not even aware of any yellow lasers that do.

#### Cyparagon

##### Well-known member

This will make more sense if explained WHY this equation works.

Energy of photon 1 added to Energy of photon 2 yields the energy of the combined (via sum-frequency generation) photon 3

e3 = e1 + e2

Energy is inversely proportional to wavelength. Raising the wavelength lowers the energy, and lowering the wavelength increases the energy. Therefore

1 / λ3 = 1 / λ1 + 1 / λ2

Re-arranging this formula using standard algebraic practices gives the formula

λ3 = 1 / ( 1 / λ1 + 1 / λ2 )
OR:
λ3 = λ1 × λ2 / ( λ1 + λ2 )

##### New member
This will make more sense if explained WHY this equation works.

Energy of photon 1 added to Energy of photon 2 yields the energy of the combined (via sum-frequency generation) photon 3

e3 = e1 + e2

Energy is inversely proportional to wavelength. Raising the wavelength lowers the energy, and lowering the wavelength increases the energy. Therefore

1 / λ3 = 1 / λ1 + 1 / λ2

Re-arranging this formula using standard algebraic practices gives the formula

λ3 = 1 / ( 1 / λ1 + 1 / λ2 )
OR:
λ3 = λ1 × λ2 / ( λ1 + λ2 )

Thanks to all of you guys for clearing that up, it seemed like the more I researched the less I understood. +rep to all of you thanks!
Edit] rep for those of you that I can

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#### paul1598419

##### Well-known member
That reminds me of the lyrics to "Heart of the Matter". "....The more I know the less understand, all the things I thought I'd figured out I have to learn again."

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#### Encap

##### Well-known member
Thanks to all of you guys for clearing that up, it seemed like the more I researched the less I understood. +rep to all of you thanks!
Edit] rep for those of you that I can

PS Dragon Lasers can't help you because they do not make anything. They are just middle man retail resellers of CNI made products. They are not even Distributors of CNI products--they are just a retail business/shop in China reselling CNI products from within China.
CNI is the only manufacturer of hand held 589nm lasers on earth for many real reasons in the real world.
see CNI's web site here: Green laser, Blue laser, Infra Red laser, IR laser, UV DPSS laser.

Why not ask CNI--- is worth a try---maybe they would be willing to sell you a crystal set that will produce a 589nm output using an 808nm pump. They do just that on a regular standard production basis---might not be any need for you to reinvent the wheel and might be a much less expensive way to put together something that produces 589nm laser light

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#### Singlemode Laser

##### Active member
So just yesterday I contacted dragon lasers about their handheld yellow pointers, I asked about how they worked. Things such as pump wavelength and processes used. Shortly after I checked gmail to find a nice letter from Adam explaining that the yellows used a 808nm pump. He did not know the exact process but I decided I could probably figure it out.

Here is how I imagine it works,

I realized that Nd: YAG emits like this,

I kind of doubt that though and either way both crystals are incredibly hard to get a hold of to emit at their 1180nm lines.

This is a spectrum of absorption and emission of Cr4+:forsterite. Not a Nd: YAG. It's spectrum looks like this:

You see four emission wavelenghts. In theory the Nd:Yag can emit all of them. Visible wavelenghts are then achieved through sum, difference or doubling frequency generation.

Singlemode

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#### Richie89

##### Well-known member
this information just made me go take some Bayer :crackup:

#### paul1598419

##### Well-known member
Hi, Singlemode. Good to see you posting again. :yh:

#### Singlemode Laser

##### Active member
Hi, Singlemode. Good to see you posting again. :yh:
Thanks,

I was pretty busy the last weeks (but now I am back to my normal schedule). Allways find it interesting to read these kind of threads, where members dig deep into laser technology and I try to help where I can.

Singlemode

GSS

#### Encap

##### Well-known member
:beer:Congratulations to Singlemode Laser on 100k +reps milestone in recognition of excellent contributions to LPF :beer:

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