How Green Lasers Work (for the newbs)

Well the question is often asked here, how do green lasers actually work and why do they need an IR filter, so I decided to make this post that people can refer to so the question doesnt need to be constantly answered.

Key words and abbreviations:

Nd : YVO4  - The crystal used to convert 808nm(IR) laser Light to 1064nm(IR) laser light
Nd : YAG - The crystal used to convert 808nm(IR) laser Light to 1064nm(IR) laser light
KTP - The crystal used to convert 1064nm (IR) laser light to 532 (Green) laser light
IR - Infra-Red
nm - nanometres the measure of the wavelength of light
Wavelength - what determines the colour of the laser e.g. 532nm = green  ,  650nm = red  ,  473nm = blue
Pump Diode - The diode used to create the laser light that is to be converted

Green Lasers and how they work

Green lasers work by changing different wavelengths of light using sets of crystals.  The crystals used in a green laser are called an Nd : YAG ( an Nd : YVO4 can also be used ) and a KTP crystal.

This is the wavelength change process :

808nm IR from pump diode > into Nd : YAG/YVO4 > 1064nm IR out > 1064nm IR into KTP > 532nm green out.

Due to the crystals only having about 30% efficency (or less) the laser will only convert around 1/3 (or less) of the 808nm IR to green meaning, if you have a 300mW pump diode, the laser its self will only produce 50-100mW of green.

Due to having all these crystals that need to be aligned certain ways, ect ect, it is nearly impossible to build a green laser at home, you would need special tools.

Why do green lasers need an IR filter?

Green lasers need IR filters because the process used to get the green uses IR lasers, now IR (or infra-red) is invisble to the human eye , so if green lasers do not have an IR filter then the IR laser light can leak and go into your eyes without you knowing and damage your eyes, or even blind you. Thats why IR filters are put into green lasers. It is advised that you do not buy green lasers that do not come with an IR filter (cheap lasers do not usually have infra-red filters), if you do you should be very careful, or install an IR filter yourself.





Hope this helps

/me

That diagram would be the difficult route. Also power robbing with the extra optics. I just finished my first, here is the link.

http://www.laserpointerforums.com/forums/YaBB.pl?num=1209525651/0

wow that pretty sweet, ive seen a few opened up home built ones but the were big

Getting them small is just the same, it just takes more patience.

yeah im sure it does, sadly i dont have too much, nor do i have IR goggles lol

here's a pic from my 200mw green while i was repairing it, it uses a Cmount diode

oooh an unusual diode

On the DX200 of mine, the steps are the same just in a different order. It goes like this

Laser diode
(808nm)
Nd:YAG
(1024nm)
KTP
(532nm)
Diverging Colaminating lens
Converging Colaminating lens
(Green 532nm laser beam)

Probably less efficient & cheaper to make.

lol i just but the collimating optics in a sort of random order because i know they can be psoitioned so many places

Hm....I thought all pen lasers use YVO[sub]4[/sub] :-/

Switch said:

Hm....I thought all pen lasers use YVO[sub]4[/sub]  :-/

Click to expand...

well i put YAG in the diagram but wrote down YVO4/YAG in the writing explaining it so that should be ok, i think YVO4 is just more efficient

Diachi said:

oooh an unusual diode

Click to expand...

Actually, a C-mount diode is quite common in quality green lasers.

The CNI pen lasers (Nova X-series) use it for example (and many others), and a C-mount often has a built in FAC micro lens, which makes for a more efficient laser with a lower probability of mode problems. Cheap powerful lasers don't use any collimation between the pump and the crystals, because the crystals couldn't handle the higher power density.

oh right .... i just thought theyd use a normal 9mm type diode or somethin like that....

and the diagram wont be the same for all lasers i just drew it roughly

Except it should be obvious to people that the Nd doped crystals used for these lasers do not lase at 1024 nm because if you frequency doubled that it would be 512 nm not 532.

Oooooh .... mistake, ill fix it just now

it was a typo, not had much sleep lateley

edit : Fixed

hey i think this would make a very nice add to the FAQ, talk with Chad or styro if you want us to add it