Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers



[PIC HEAVY] Got a Monochromator!

Cyparagon

Well-known member
Joined
Sep 12, 2007
Messages
9,643
Points
113
^Say, why haven't we seen yours? Pictures/thread hereby requested :)
 



The Lightning Stalker

Well-known member
Joined
Aug 14, 2013
Messages
2,655
Points
63
Lol, well it's a bit more humble than the others. A general outline of the setup can be found in
this post:

http://laserpointerforums.com/f42/what-do-your-diffraction-glasses-i-wavelength-determination-42599.html#post1230142

I'm working on getting a glass grating for more accurate results. There will eventually be a
custom stand for the grating and DUT as well. I got a few Al bars and misc. pieces to put
something together with the other day.

The grating is positioned a set distance from a white ruler. (Usually 100mm) The pattern
is then photographed.

Here is the pattern from a 940nm diode:

660nm:

Then the distance from the center to the first order line is plugged into this:


The results are accurate within ±5nm or so. No lens or slit is needed for a collimated laser
beam source since it is already narrow and has its own lens. I'm still trying to figure out
how to get a good spectrum through a pair of LSGs. bloompyle's PCM would work great
for that.
 

Cyparagon

Well-known member
Joined
Sep 12, 2007
Messages
9,643
Points
113
That's a grating and a formula - not a monochrometer. I did a write-up on that method a couple years back. That's quite a complex formula as well. You can simplify it to:

λ = dsin(arctan(S/L))

Where d is the distance between the slits (10^-6 meters for that grating), S is the distance between the diffraction orders (in meters), L is the length to the screen (in meters), and λ is the wavelength (in meters)
 
Last edited:

Atomicrox

Well-known member
Joined
Jun 22, 2011
Messages
2,432
Points
83
I'm not 100% sure this is safe (please confirm before trying), but have you tried shining the laser at a white paper in front of the entrance slit and looking directly into the exit slit?

Should work with low power lasers, right?
 

Wolfman29

Well-known member
Joined
Jan 14, 2011
Messages
3,830
Points
63
Probably not a good idea. Anyway, I got a PCM from Sam so I don't need to do that! In fact, I set up a little circuit that'll detect it for me :D
 




Top