Lamba Measurement

Hey all,

I'd like your opinions about this product...
http://www.verityinst.com/SD1024D.html

It's a $20,000 instrument used to measure wavelengths for all sorts of things... It's nothing special (over Ocean Optics) besides the extremely powerful software.

So, I ran into some of these recently and have been trying to get some info and application possibilities for me (great price!)... and I suppose my major concern is as follows:

- I know this unit can measure wavelength down to less than a nanometer in accuracy, but is there a better deal on something that can do the same thing?
- Is there a more conventional (hobby-oriented) way of measuring exact wavelength without using THIS method? (much thanx to the poster, and I like the breadboard-style floor BTW ;))
- Do you guys advise such a purchase? :rolleyes:

I did actually recently purchase some linear CCD elements and did get started making my own setup, and then slowly drifted away and stopped... :o But I suppose that can become an option again

Thanx in advance;
DDL

I LOVE my USB4000 :)

How much are you paying for the software?

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Originally Posted by Laser Ben

I LOVE my USB4000 :)

How much are you paying for the software?

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I'm not buying the software... I'm buying the unit, and it has a very powerful software with really (useless to me) complicated algorithms and the such...

Aside from that, I'm fairly certain that if I can get a USB4000 for the price I am paying for this one, I would go for the Ocean Optics solution. I'm slightly worried the software would be far too complicated to offer the really simple measurement I want to do... :confused: (I did ask for the DLL to make my own though :cool:)

--DDL

For visible lasers You can get a used monochromator out of a spectrophotometer on ebay for 30-60$ and hit one nanometer easily. Considering when you only really need it is pump diodes, leds , and red diodes and dye lasers, are you sure you want to invest in one? Ie every thing else laser is locked to a atomic transition and you need a huge spectrometer to see those drift.

1200 line or 2400 line holo grating replicas are cheap, and you cal them with a hene or a neon lamp.

I own one ripped out of a spectrophotometer. I worked on ones that could see a argon laser drift 10 ghz.

Tell me what you want it for??? Do you want to measure adsorption or emission or what?
Steve

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Originally Posted by mixedgas

Tell me what you want it for???

Steve

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To get a precise reading of the wavelength of a laser diode... :o

I want to know if I'm 'seeing' things right I guess...

--DDL

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Originally Posted by mixedgas

For visible lasers You can get a used monochromator out of a spectrophotometer on ebay for 30-60$ and hit one nanometer easily.

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Would this work?

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

Thanx;
DDL

You can get a USB2000 for a little over $2k and that includes the software. I can send you a copy of spectra-suite if you want.

I'm actually getting this for about 1/4 of what you quoted... :D

--DDL

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Originally Posted by daedal

I'm actually getting this for about 1/4 of what you quoted... :D

--DDL

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

-Adam

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)

[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

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Originally Posted by sugeek

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

-Adam

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

Thanx;
DDL

Quote:

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Originally Posted by shrad

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)

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

Thanx;
DDL

[quote=mixedgas;89925]

Quote:

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Originally Posted by daedal

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

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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? :confused:

Thanx;
DDL

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