Make Your Own Spectrometer for Under $1

HydroSean · Oct 14, 2016

Those aren't the gratings I used, the ones I have are rainbow colored. If you want I'll send you a few of mine that I've verified free of charge to you. I'll cover shipping as well just PM me

CaliKirk · Oct 14, 2016

HydroSean said:
Those aren't the gratings I used, the ones I have are rainbow colored. If you want I'll send you a few of mine that I've verified free of charge to you. I'll cover shipping as well just PM me

Thank you so much for the offer, I purchased a ten pack earlier today and they should be here next week but seriously :thanks:

Im going nuts without truly knowing :banghead:

Atomicrox · Oct 14, 2016

CaliKirk said:
I only have the link to the sellers store - LEDgroup - I don't really remember which exact listing it was as e bay deleted my previous purchases from earlier this year. The thing I do know are the lasers were labeled "laser 301". I went through many different sellers and had worse luck with ones labeled YL laser, SL laser, Laser 303, 303 laser, 301 laser and the ones I kept rebuying did not have a star cap and were labeled laser 301. Sorry for not really helping on that, ill try to find out! It definitely was a gamble through every seller but this one i purchased the most from.

Thanks, let us know if you remeber the exact one.

lazeristasUVISIR · Oct 14, 2016

Some 8 years ago I was working on a 473-nm laser, and when I measured its spectra it had more lines than I wanted. I dig out an old article with information about Nd3+:YAG possible lines. (The article is https://doi.org/10.1103/PhysRevB.10.2566 ).

For green generation these are important:
1052.13
1055.05
1061.58
1064.18 (the main)
1064.55
1068.26
1073.85
1078.0

Some are quite weak some are not. While the main way for green is SHG with 1064.18->532, some visible lines can be created with the strongest 1064.18 and some other weaker by Sum Frequency Generation (SFG).

As for a reference measurement, take CD, DVD, or Blu-ray and try their gratings to compare your results.

paul1598419 · Oct 14, 2016

While I've been aware of the second harmonic generation of the main line for some time, I was not aware of the sum frequency generation of the weaker ones. I wasn't able to find a reference for it in the article you posted. If you have a link to that, would be interested in reading it.

lazeristasUVISIR · Oct 14, 2016

paul1598419 said:
While I've been aware of the second harmonic generation of the main line for some time, I was not aware of the sum frequency generation of the weaker ones. I wasn't able to find a reference for it in the article you posted. If you have a link to that, would be interested in reading it.

I've only two pages. The article is not about SHG nor SFG., it's about NdYAG lines (energy levels) and their properties (cross sections, branching rations)
That conclusion (multiple green lines) comes from my knowledge about laser and nonlinear processes. I can not provide any reputable source now for you to read on this matter. Though a laser book and nonlinear optics book should be sufficient.

paul1598419 · Oct 14, 2016

Atomicrox said:
405nm is no good for this. They vary by as much as 10nm.
It has to be DPSS or gas.

I was talking about under driven 405nm lasers. Yeah, if you have an over driven 12X or 16X, it will not give you a good 405nm wavelength. I used an 80 mW 303 405nm to test the wavelength and came out with 404.6nm.

lazeristasUVISIR · Oct 14, 2016

paul1598419 said:
I was talking about under driven 405nm lasers. Yeah, if you have an over driven 12X or 16X, it will not give you a good 405nm wavelength. I used an 80 mW 303 405nm to test the wavelength and came out with 404.6nm.

Even at normal conditions those diodes variate in wavelength from one to another. Once had ~414 nm :undecided:

diachi · Oct 14, 2016

lazeristasUVISIR said:
As for a reference measurement, take CD, DVD, or Blu-ray and try their gratings to compare your results.

As stated earlier, they vary too much. Temperature/current/variations between diodes will all affect wavelength for this to be a good method.

Gas or a known single line, stable DPSS are the best options.

lazeristasUVISIR · Oct 14, 2016

diachi said:
As stated earlier, they vary too much. Temperature/current/variations between diodes will all affect wavelength for this to be a good method.

Gas or a known single line, stable DPSS are the best options.

What I meant: take a real CD, DVD or Blu-ray (not LDs). Those discs can be used as gratings :wave:

paul1598419 · Oct 14, 2016

lazeristasUVISIR said:
Even at normal conditions those diodes variate in wavelength from one to another. Once had ~414 nm :undecided:

I haven't made it a mission to test the wavelengths of many various laser diodes. I did do a cursory measurement of several cheap laser pointers to see where they actually fell in the wavelength spectrum. Aside from one that claimed to be 650nm and measured 660nm, they were all fairly close.

diachi · Oct 14, 2016

lazeristasUVISIR said:
What I meant: take a real CD, DVD or Blu-ray (not LDs). Those discs can be used as gratings :wave:

Ahhh, my mistake, yep, right you are! :beer:

Sta · Oct 14, 2016

I received my multiline 301 from CaliKirk today, and performed the wavelength test on it using a 3rd order diffraction from a 50 l/mm grating at 21.57 meters.
Shockingly, I got the same result -- 527nm. Then I tested "another" 532, and got 532.
This makes no sense. Everything we've ever known tells us 1064 is the primary transition of ND:YAG and ND:YVO4!

diachi · Oct 14, 2016

Sta said:
I received my multiline 301 from CaliKirk today, and performed the wavelength test on it using a 3rd order diffraction from a 50 l/mm grating at 21.57 meters.
Shockingly, I got the same result -- 527nm. Then I tested "another" 532, and got 532.
This makes no sense. Everything we've ever known tells us 1064 is the primary transition of ND:YAG and ND:YVO4!

Does Nd:YAG/YVO4 have strong transitions at 1054nm? Perhaps so (need to do some digging...) - in which case, mirrors that are coated incorrectly could be responsible for the 1055 line lasing instead of 1064nm. Or perhaps it's the crystal assemblies failed QC for 532nm output (Due to incorrect coatings) but they were used anyway?

Closest other medium I can think of is Nd:YLF which has strong transitions at 1047nm and 1053nm. So maybe they are using that instead ... for some reason? I'd need to do more digging and more testing. Spectroscope with a bandpass filter for IR may give a better indication there.

Sta · Oct 14, 2016

Well, it would be 1055, as I got 527.6.
Still unusual. Should not be happening.

Benm · Oct 15, 2016

I think these patterns are due to internal reflections in the foil. The light just bounces between the surfaces just as it does in a pane of glass, giving some lines in places they should not be.

A 532 nm DPSS laser should not produce other wavelengths. The doubling process is very selective when it comes to incoming wavelength, which is 1064 nm from the solid state.

If the emission was as broad as the pictures suggest it should actually be very easy to construct green lasers anywhere between 525 and 531 nm just by adjusting the reflective coating. Realistically something like that is not possible (try to find any such lasers for sale), and i think it must simply be an artefact of using this type of grating.

Make Your Own Spectrometer for Under $1

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