Lamba Measurement

[mixedgas]

[quote=daedal;89846]Would this work?

I always thought these things have a really tight 'incidence angle' requirement... otherwise the reading is bogus...

yeah, but nothing 1 foot of fiber and a collimating lens, or a f/2 lens wont cure. Heck on mine, I just added two slits 6" apart.
Thats what the hene is for, a good sanity check. Neon lamps are your friends as well on calibration, but be aware a dpss yag can be as much as 1.1 nm wide in the green line.

The grating/ccd ones have the same problem, as well.

That one looks good, except I'd ask the seller to shoot a tight picture of the dial as it looks like it took a hit to the faceplate.

Steve

[daedal]

If it doesn't work out for you let me know!

-Adam

I hope it does work, but will let you know either way

Thanx;
DDL

[daedal]

you try the way of the michelson interferometer

the moving mirror makes interference fringes proportional to wavelength composition of the spectra entering the interferometer

if you acquire these varying interferences with a rapid Si photodiode and then apply a fast fourier transform on the measured signal, what you have is then a composition of the light spectra entering the interferometer

calibration is done with a HeNe and another lower wavelength laser like an argon or so

if the scale is non linear, you can try to interpolate the other wavelengths using a polynomial function that matches the two (or three) calibration points in the spectral range you want (might be highly inaccurate outside the range boundaries)... but any usable precision would require at least 10 different calibration wavelengths

however, I think that this polynome should be fairly easy to find somewhere like universities or so, who frequently use professional michelson interferometers (as we use where I work)

Thank you very much for the input and the help... But this seems like it, too, will be incident-angle specific....

Thanx;
DDL

[daedal]

[quote=mixedgas;89925]

Would this work?

I always thought these things have a really tight 'incidence angle' requirement... otherwise the reading is bogus...

yeah, but nothing 1 foot of fiber and a collimating lens, or a f/2 lens wont cure. Heck on mine, I just added two slits 6" apart.
Thats what the hene is for, a good sanity check. Neon lamps are your friends as well on calibration, but be aware a dpss yag can be as much as 1.1 nm wide in the green line.

The grating/ccd ones have the same problem, as well.

That one looks good, except I'd ask the seller to shoot a tight picture of the dial as it looks like it took a hit to the faceplate.

Steve

I do like the slits idea as that is easily doable to pretty much any solution... With the monochromator as above, do you get some kind of indication of how 'much' light is there?

Thanx;
DDL

[mixedgas]

The monochromator is just a transfer function between you and your photodetector, you can pretty much put anything at the output.
usually you get 40-60 out of what you put in on a given line. I usually recommend diffusing the laser a bit to prevent Rowland's ghosts
in the readouts, subtle errors in the surface of the grating come back as noise at really high power, as do second order reflections off the grating under a few circumstances. Its really not that critical if you have a few milliwatts.

Steve