AOM's and PCAOM's

[robotarmy]

Hi there,

I've been in contact with Gogu recently about purchasing an AOM chip for my argon laser, and he sent me a very intriguing link to a lab at Niagra college in Ontario that uses an AOM chip as a PCAOM by driving it with a tuneable RF source.

http://technology.niagarac.on.ca/cou...SwitchAOM.html

I'm wondering if anyone here has any idea how this can be done. I'd really like to be able to select a line from my ALC68.

Here's what i (think i) know about AOM chips:
The beam passes through the chip at the bragg angle. Depending on some property of the input waveform to the piezoelectric crystal attached to one end of the crystal a portion of the incident wave is diffracted. The primary beam that passes through the crystal is the 'zeroth mode' beam, the first diffracted beam is the 'first mode' beam, etc.

The output from the driver to the piezoelectric chip is an RF modulated signal at some frequency, with some waveform, and with some signal modulated on top of it.

What i'm guessing:
If I can use a pair of tuneable RF sources, one for each of the lines from my argon, sum their outputs together and amplify them as needed, they would be able to drive a suitable AOM chip as a 2-channel PCAOM chip... that's a total guess tho.

My questions basically are:
What are the properties of this waveform and how do they affect the output of the crystal?
What are the differences between AOM and PCAOM crystals and drivers?
What would the requirements of a AOM driver be to allow it to act as a PCAOM, and could such a beast be constructed from off-the-shelf or surplus RF components?

[sugeek]

Steve (Mixedgas on PL) is the person you want to talk to about this. He has mentioned something about a 4 channel in a past thread I didn't find in 30 seconds.... This thread should be of some help: http://www.photonlexicon.com/forums/...s-a-PCAOM-work

If you are looking to buy an AOM gogu can hook you up! http://www.photonlexicon.com/forums/...river?p=130641

[robotarmy]

Steve (Mixedgas on PL) is the person you want to talk to about this. He has mentioned something about a 4 channel in a past thread I didn't find in 30 seconds.... This thread should be of some help: http://www.photonlexicon.com/forums/...s-a-PCAOM-work

If you are looking to buy an AOM gogu can hook you up! http://www.photonlexicon.com/forums/...river?p=130641

Thanks very much for the tips I'll have another good search around the forum for more about PCAOM's, It seems at the very least the driver's going to be something like 2x VCO's, RF mixer and amp, and since the AA crystal is TeO, it should technically work as a PCAOM... After that it's just a matter of tuning the driver, of course none of these things are easy, but hey, such is life.

Always with the questions i know, but do AOM's work for multiline argon lasers? (i.e. until i try sorting out this PCAOM business will the AOM blank the whole beam even if it's got more than one wavelength component?)

Gogu is the one that tipped me off to the lab i posted a link for, like i mentioned he's the one i've contacted about purchasing the AOM's, word on the street is they're a good deal and he's good to deal with

Steve is the original don of all things related to my laser, he's already helped me out HUGE with info about this argon laser, so i'm reluctant to harass him again until he recovers from my previous inquiries

[gogu]

Kvant have the same aoms with different drivers for the 440-480nm here:
http://www.lasershow.sk/bazzar
more $, but it might be of interest..

[robotarmy]

Kvant have the same aoms with different drivers for the 440-480nm here:
http://www.lasershow.sk/bazzar
more $, but it might be of interest..

Yeah, for sure! I'm going to look into getting a multichannel driver going, but until then i'll stick with just a single channel.

Gogu i'll be in touch with some money this week

[mixedgas]

[QUOTE=robotarmy;130821]Thanks very much for the tips I'll have another good search around the forum for more about PCAOM's, It seems at the very least the driver's going to be something like 2x VCO's, RF mixer and amp, and since the AA crystal is TeO, it should technically work as a PCAOM... After that it's just a matter of tuning the driver, of course none of these things are easy, but hey, such is life.

The angle of the crystal is different in a pcaom then a AOM. You can get a AOM to select 1-2 lines at a time at low transmission.

BY angle in this case, I mean the angle to the crystal structure, in x,y, and z.
They use X ray crystallography to orient the AOM and PCAOm crystals. PCAOM also has a sort of prism face cut into the crystal.

If you insist on doing it the hard way, a patent is here:

http://www.google.com/patents?id=N3A...age&q=&f=false

note that crystal is 4 inches long...

and here: http://www.google.com/patents?id=I0M...age&q=&f=false

you can select 1 (one) color at a time using a plain jane AOM if you FM modulate the carrier.

Steve

[robotarmy]

[QUOTE=mixedgas;131173]

Thanks very much for the tips I'll have another good search around the forum for more about PCAOM's, It seems at the very least the driver's going to be something like 2x VCO's, RF mixer and amp, and since the AA crystal is TeO, it should technically work as a PCAOM... After that it's just a matter of tuning the driver, of course none of these things are easy, but hey, such is life.

The angle of the crystal is different in a pcaom then a AOM. You can get a AOM to select 1-2 lines at a time at low transmission.

BY angle in this case, I mean the angle to the crystal structure, in x,y, and z.
They use X ray crystallography to orient the AOM and PCAOm crystals. PCAOM also has a sort of prism face cut into the crystal.

If you insist on doing it the hard way, a patent is here:

http://www.google.com/patents?id=N3A...age&q=&f=false

note that crystal is 4 inches long...

and here: http://www.google.com/patents?id=I0M...age&q=&f=false

you can select 1 (one) color at a time using a plain jane AOM if you FM modulate the carrier.

Steve

Gah, i thought there might be a difference in the physical orientation of the crystal...

Is the university lab i posted just going ahead with theirs and taking huge losses in beam power then?

[mixedgas]

[QUOTE=robotarmy;131188]

Gah, i thought there might be a difference in the physical orientation of the crystal...

Is the university lab i posted just going ahead with theirs and taking huge losses in beam power then?

reread the experiment. The hene is done with a CT AOM. The megadollar RGB hecad (Dr Cesele gets folks to fund his hobby while teaching, must be nice!) goes to a PCAOM. The writeup should say," You learned to do a Bragg angle once, now dont let the PCAOM intimidate you....."

Now, the older xerox aoms have a slightly tilted prism face on them and a VCO input, I have, in the lab, some years ago, gotten them to easily select lines with the built in electronics. The angle is small, and you need a long beam path, but it can be done. That older xerox driver tunes from 100-130 mhz. can you route two vcos into a mixer and get two lines, yes, but the total power might be low as you cant overdrive the crystal. more then 2 lines ina short AO, fergetttabout it...

My saying NO, DOES NOT mean you should not try the experiment. It just might say I know what you get......


NOW if you were to have 4 oscillators (AND YOUR SEEING THIS IDEA PUBLISHED HERE FOR THE FIRST TIME EVER FOLKS) and broke each image point down into 4 or 8 time slices, and you gated the RF for each color from each oscillator to the AOM during its own time slice, plus or minus a little delay for propogation, you could have a standard AO modulate colors. BUT you need a cooperative point clock from the software to do it right.. considering 1/30,000 = .000333 second div by say 4 then inverted means = 120 kilohertz, still within the bandwidth of the AO, you now get 1/4 the total power, but you would get color control. IE this is the rough idea of field sequential color used in TV, adapted for laser using a simple AO.

The above paragraph is copyright 2010, all rights reserved, O. Steven Roberts

Steve

[robotarmy]

[QUOTE=mixedgas;131244]

reread the experiment. The hene is done with a CT AOM. The megadollar RGB hecad (Dr Cesele gets folks to fund his hobby while teaching, must be nice!) goes to a PCAOM. The writeup should say," You learned to do a Bragg angle once, now dont let the PCAOM intimidate you....."

Now, the older xerox aoms have a slightly tilted prism face on them and a VCO input, I have, in the lab, some years ago, gotten them to easily select lines with the built in electronics. The angle is small, and you need a long beam path, but it can be done. That older xerox driver tunes from 100-130 mhz. can you route two vcos into a mixer and get two lines, yes, but the total power might be low as you cant overdrive the crystal. more then 2 lines ina short AO, fergetttabout it...

My saying NO, DOES NOT mean you should not try the experiment. It just might say I know what you get......


NOW if you were to have 4 oscillators (AND YOUR SEEING THIS IDEA PUBLISHED HERE FOR THE FIRST TIME EVER FOLKS) and broke each image point down into 4 or 8 time slices, and you gated the RF for each color from each oscillator to the AOM during its own time slice, plus or minus a little delay for propogation, you could have a standard AO modulate colors. BUT you need a cooperative point clock from the software to do it right.. considering 1/30,000 = .000333 second div by say 4 then inverted means = 120 kilohertz, still within the bandwidth of the AO, you now get 1/4 the total power, but you would get color control. IE this is the rough idea of field sequential color used in TV, adapted for laser using a simple AO.

The above paragraph is copyright 2010, all rights reserved, O. Steven Roberts

Steve

Still a bit over my head but i'll read it a few more times and try to digest it! I could have sworn gogu said the AOM he was selling was used as a PCAOM in that lab, maybe we're both mistaken. The thing is, i'm not going to be trying to select any more than two lines from this laser, as it's just an argon and there's only two lines worth selecting from. Do you think it's still worth learning about RF and lasers at the same time and trying the experiment with a two-channel driver?

[mixedgas]

yes, RF is a useful skill, at VHF its fairly easy, and worth learning. I will help you.
This can be done cheaply.

Steve