Interesting budget AOM

[Phat Photons]

Hi all,
I got one of these a while back:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=200415555775

It seems to be a dual channel AOM with some birefringent beam displacers and 1/2 wave plates set up such that an unpolarized HeNe is split in to two parallel beams one horizontal polarization the other vertical. The polarization of one of the beams is rotated from horizontal to vertical such that both beams are vertically polarized. The beams then pass through the two channels of the AOM. The other beam is then twisted to horizontal with another 1/2 wave plate and recombined with another birefringent displacer.

I suppose you could use prisms to make a chromatic displacer that would say take in coaxial blue and green displace the beams to go into the channels of the AOM. Another set of prisms could then recombine the beams.

From my early testing the AOM runs at 350MHz and gives a respectable beam deflection. The driver does analog modulation.

Ed

[flecom]

they have been selling those things for years... have you figured out how they function? I think most people ignored them because there is (was) no documentation for them

[mixedgas]

I work with RF at the professional level. Most xerox drivers can be converted to analog. If somebody takes me a picture of the driver internals, I'm willing to bet that like most xerox drivers, it can be converted to 0-5V modulation with full ANALOG control.

Steve

[mixedgas]

I suppose you could use prisms to make a chromatic displacer that would say take in coaxial blue and green displace the beams to go into the channels of the AOM. Another set of prisms could then recombine the beams.


end quote
Dichro split and combine color. Done that , years ago, got the tee shirt. Since most DPSS are ALREADY polarized, it might just be possible to use the module as is, and use the existing recombiner. Dont use a prism, use a blue reflect green dichro.

Steve

[Phat Photons]

If I recall correctly the modulation inputs each go straight into a minicircuits mixer. The final amps are CATV style gain blocks. I'll grab a pic tonight.

Dichro split and combine color. Done that , years ago, got the tee shirt. Since most DPSS are ALREADY polarized, it might just be possible to use the module as is, and use the existing recombiner. Dont use a prism, use a blue reflect green dichro.

I was thinking about that after my post. The question would be is whether the 1/2 wave plate would cooperate at green and blue wavelengths. The dichro on the input would be good since there will be one anyways. It makes sense to avoid 4 un-coated prism surfaces.

The current splitter/combiner setup is coated for red and the losses stack up with other wavelengths. There are no less than 12 surfaces for a given polarization beam to pass through.

Pulling the input splitter and one 1/2 plate would cut 4 surfaces in one path and 6 in the other.

It looks like the beam would need to have a waist of maybe 100um in the AOM. It would probably be easiest to have a lens on green and blue independently to get two parallel beams going through the AOM. The beams would need to be about 0.5 to 1mm apart(I'll try to post that dimension tonight) when passing through the AOM.

[mixedgas]

If thats the case, 0-6 mA of current down the minicircuits mixer usually results in nice modulation. You may need to remove, replace or bias some PIN diodes if it is like every other xerox.

Your in Cleveland? I'm from Akron, I'm back every two-three weeks.

You need to get to know Dr Lava and Agent C

They are in your neck of the woods.

steve

[mixedgas]

You would only need maybe 5-7 optics. A pair of of telescopes for the focus, and the dichro.

Steve

[Phat Photons]

Ok,
here is a shot of the RF deck.


and here is one of the AOM out of it's case:




It looks like the two channels are spaced 350um apart.

The modulation must come directly in to the RF port, as it has response down to DC. The LO and IF ports of the SBL-1X are transformer coupled and would not offer DC response.

In the relatively near future I'll try some quick checks on the 1/2 wave plates to see if they behave at green and blue wavelengths.

Ed

[mixedgas]

Wow, two 2810s. A 2810 is a powerful enough amp to drive a 4 channel pcaom.

the usual high quality xerox AO crystal. Thats a steal

Somebody got smart and eliminated the pin diodes I was worried about.

Direct drive is fine. Thats a nice package. easily modded to drive a 80 mhz or 110 mhz ao as well.

34 dB 10-450 MHz 800 mWATT WIDEBAND LINEAR AMPLIFIER

make sure the series resistor on the dc coupled port is the right value to protect the mixer and your RGB source and your good to go.

The waveplates will suck starting 5-10 nm off their design wavelength. 50 nm away and they are near useless. Again, a redesign to avoid waveplates is in order.

Steve

[DZ]

Meredith lists the same item on thier website for $10 less than their auction.
http://www.mi-lasers.com/cgi-bin/sho...on&key=P-AOM-1