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FrozenGate by Avery

Cheap way to measure laser wavelength

Skittles

Skittles

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Nov 6, 2017
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Not long ago I came across an interesting youtube video about measuring wavelengths of lasers, its fairly recent and I haven't seen a post about it here, so I'm guessing most people don't know about the video or the method the youtuber proposes in it.

Here it is: https://www.youtube.com/watch?v=i9WS7Jo2TAY

I thought it was very cool so I decided to buy a diffraction grating and try it my self, I don't have a big ruler so I used measuring tape :D its harder with it but that's all I had.

So far I tried this with just two lasers and with at least 10 attempts.
First my LaserBTB pen, it has an amazing perfect symmetrical round dot which made it easier for measuring, multiple attempts had me at 528nm - 530nm until I got the setup as perfectly aligned as possible and here are the final results:

8QhvfRO.jpg

Pretty close to the advertised wavelength, I am happy with that number.
Next I tried Sanwu pocket 505nm:

zhrNH5p.jpg

Also very close.

Pics of my setup:
nNv7AOR.jpg

co7Krv2.jpg


Conclusion: My final results were pretty close to the advertised wavelengths, but I do not wish to state that that's what the actual wavelengths of these lasers are, my setup was not perfect, and I used a closet door instead of a solid wall. (I had my reasons :D) Maybe if you get a laser and you have no idea what wavelength it is, this is one way to measure it. Nevertheless it was fun and I thought it was important enough to share. :beer:
 
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Ive been thinking about that video too since seeing it. Nice to see someone do it with good results!
 
Cool!
I tried this several years ago to check some PHR-803T diodes that seemed to vary in brightness at the same power output.
It's nice to see you got pretty good results.
Thanks for sharing. I like to see this kind of stuff.
 
It is a very good method on a budget. But the drawbacks is accuracy. It is highly dependent on the setup, observation and measurement, and optics specs. Importantly, it is vital to know exactly how many lines per mm your grating is if you are going for accurate measurements of unknown lasers. For that you then need a laser of which you do know the wavelength, which is usually a HeNe.
 
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These have popped up here from time to time. I used to use a sheet of 1000 l/mm to cut gratings from to try to measure wavelengths prior to getting my USB2000. It is important to get your setup perfect and the distance from the grating to the wall you are measuring the distance from the 0th order maxima to the 1st order maxima as far away as possible. This helps to get the most accurate measurement possible. Since then, I have cut sheets off my 20 cm^2 grating to send to members who want to try this.
 
Ultracrepidarian, It's a good video, and it's been a while since this method has been discussed, and since we've always got new members coming on board, it's nice to see a review of how this is accomplished. :yh:

The guy that made this video stressed accuracy and careful measurements to get quality results, except that he used a relatively short distance to the wall as some others have already mentioned.
 
Wondering if that will work with higher powered lasers or if it will melt the diffraction grating. It has to be focused to get accurate results so unfocusing it probably won't be an option.
 
I've had a first-gen 1W WL Arctic ruin one of my high school science teacher's diffraction gratings, though I'm not sure which kind of grating it was... It's been too long...

I have a bunch of the 1000 lines/mm ones shown in the OP that I can try to ruin with my 900mW 405 and 2W 472 this weekend. I don't mind since they're so cheap.
 
I have a sheet of 1000 l/mm that looks clear. I have used over three watts through it without it even getting warm. The gratings in spectrometers are mirrored and made of metal. But, I would destroy the optical pickup if I couple three watts into it directly.
 
BowtieGuy said:
Ultracrepidarian, It's a good video, and it's been a while since this method has been discussed, and since we've always got new members coming on board, it's nice to see a review of how this is accomplished. :yh:

The guy that made this video stressed accuracy and careful measurements to get quality results, except that he used a relatively short distance to the wall as some others have already mentioned.
Click to expand...

Glad I did something positive for once. :D
ZRaffleticket said:
I've had a first-gen 1W WL Arctic ruin one of my high school science teacher's diffraction gratings, though I'm not sure which kind of grating it was... It's been too long...

I have a bunch of the 1000 lines/mm ones shown in the OP that I can try to ruin with my 900mW 405 and 2W 472 this weekend. I don't mind since they're so cheap.
Click to expand...

Mine is 500 lines/mm, got it from here: https://www.ebay.com/itm/Diffraction-Grating-Slide-Linear-500-Lines-mm-Holographic-Physics-Spectrum-Color/280730031268?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D51377%26meid%3Ddbd37af3752a47cb8b07e6a7ca944635%26pid%3D100675%26rk%3D2%26rkt%3D15%26mehot%3Dpp%26sd%3D282937608173%26itm%3D280730031268&_trksid=p2481888.c100675.m4236&_trkparms=pageci%3Ad84c234a-484d-11e8-babe-74dbd180da05%7Cparentrq%3Afb62d5f11620ad4b134dc327fff9d3ce%7Ciid%3A1 Its from Israel and the seller didn't give me tracking info, but it came pretty quickly.
 
The more lines/ mm the more accurate your measurement should be. If you would like a large piece of clear 1000 l/mm grating, Ultracrepidarian, PM me with your address and I will mail you one free of charge. :D
 
paul1598419 said:
The more lines/ mm the more accurate your measurement should be. If you would like a large piece of clear 1000 l/mm grating, Ultracrepidarian, PM me with your address and I will mail you one free of charge. :D
Click to expand...

Thank you for the offer Paul I'll think about it. :)
 
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