ฝัง
- เผยแพร่เมื่อ 14 ต.ค. 2024
- Episode 31
#DIYLaserControl
#LaserModulation
#AcoustoOpticTechnology
AOTF AOM PCAOM Controller for Under $100!
In this episode I take a look at an Acousto-optic Tunable Filter!
This device allows us to modulate or pick a wavelength from a multiline Laser using very high frequency sound waves, that are coupled into a crystal using a Piezoelecric transducer.
Since this did not come with a controller, I show you how to build a controller for these devices for under 100 bucks, using an inexpensive Voltage controlled Oscillator (VCO) and an RF Amplifier!
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Wiki Article: en.wikipedia.o...
Data Sheet: www.laserland....
Schaefer-Bergmann diffraction pattern: ieeexplore.iee...
BOM:
70-200MHz VCO RF Signal Source Voltage Controlled Oscillator Signal Generator :
www.ebay.co.uk...
2MHZ-700MHZ 3W HF VHF UHF FM Transmitter RF Power Amplifier Module For Ham Radio:
www.ebay.co.uk...
LM317 DC Linear Regulator module:
www.ebay.co.uk...
...and a well stocked parts bin ;-)
See also: • The Laser Shifting Pol...
#Laser #acoustooptics #optics
Great timing!
Been Rolling around with kidney stone pain… And I get a few hours relief every now and then…… It’s nice to catch up on the TH-cam laser content 😁
Ooft! I hope you get well soon! Glad I am providing a little relief :-D
Thanks for putting this all together, great work! In fact I had seen these little RF amplifiers on ebay and wondered how well they work. Now I know!
I am glad you enjoyed it! Yep they are cool little devices and I am sure you will find a use for one at some point!
It would be really interesting if you get you hands on one of these, I hope you can do some lithography stuff with it. 😃
Very nice build man! I have greatly enjoyed living vicariously though your projects -great job Les, thank you!
Thanks! Glad you are enjoying them!
In 1995 we used it in laser shows, device was built by a ukrainien university. It was a beauty
I came to the channel for the supercontinuum and browsing the other vids I found a vco chip that I can use for one of my own projects! I was looking for a cheap vco to use in a phase locked loop, but all I could find were very expensive, covering Ghz. I only need for my application 30Mhz so that mc1648 will do very nicely. Great channel content!
Thanks! I am glad this stuff is helpful!
Thank you so much for this, i have been trying to make an AOM driver and this video has given me some well needed direction
Awesome! Glad you found it helpful.
Thanks Les - really like the way you do things
Thanks!
Very awesome video! The cool thing I noticed is that these also will rotate the polarization of a laser beam as well which is an interesting effect. When I get a white light Ar-Kr laser going I want to revisit PCAOMs and related devices. A friend of mine also said strange effects visually happen if you view a white LED through one during operation. Non-linear optics make fore some of the most fascinating crystals on the planet!
Cool! Yeah I had thought about polarization, but haven't gotten around to playing with it yet.
One of the first things I tried was a white LED, but I could not see any changes, that said, I did not collimate the beam, so perhaps it is worth revisiting...
For sure, there are some really interesting phenomena!
@@LesLaboratory You may want to try placing a polarizing filter in front of the LED so that it is much more efficient for the crystal. I figure the angle you would also see the change at would be quite narrow as well. It would be a tricky thing to visually see all in all. I have yet to try myself.
Nice work on the ebay built AOTF driver - handy to know that it's possible to build!
Thanks!
Amazing…. So nice to see. Thanks for sharing.
Thanks!
Great video as always, thank you.
One other interesting effect of those AOMs is that they will shift the frequency (hence wavelength) of the laser beam by the same frequency you fed into the crystal with your RF source. You can use this effect for many applications.
Can it form a picosecond pulses for say fluorescence lifetime analysis?
@@nvspraneeth901 I think Pockels cells are typically used for anything beyond the nanosecond range.
These can be driven at several frequencies at once to stack wavelengths on top of one another. They were commonly used for color modulators in the ArKr mixed gad ion laser days of laser light shows. They were also used in biotech equipment for scanning florescent stained samples with a multiline arkr laser. Keep it clean as TeO2 does not like cleaning by nornal solvents. 🤔🤓❤
I was that in the manual, but wanted something quick and dirty. Thanks for the advise on cleaning, the intent was not to touch it anyway as TeO2 is soft stuff, but I might have been tempted by solvents!
Maybe you can give some insight on a curious laser physics note that has very long intrigued me. On the Hyperphysics website under the page for Brillouin scattering, there is a diagram showing "laser water scattering" using a helium neon laser that is supposedly demonstrating the creation of side bands on either side of the 632.8nm He-Ne line due to *phonon* creation/annihiliation by the beam's passage through water. I don't have access to the paper referenced and I've never heard about the phenomenon elsewhere or ever seen it demonstrated. I don't think it's related to Raman scattering, but is something totally different that I don't really understand. It would be really great to see someone demonstrate what this is on youtube.
That would be a cool but very involved project! It seems to require a hyper-fine spectrometer to see the Brillouin Shift. I wonder though if it is possible to do it on the cheap...
Awesome to see man! Excellent work as always for the layman and/or head traumatized scientist as well. I experienced a Brimrose AOTF-NIR for a few to assess feasibility for process analytical technologies and lab testing of pharmaceutical raw materials. Interesting the capabilities for spectroscopy. Is there a spectrometer build using potential in the future?
Thanks! Those look like cool devices, are they using white-light sources? Well, maybe then! I will have to try some more experimentation with it to see what is possible.
@@LesLaboratory Yes, reads like a Tungsten (Tungsten Halogen) white light source. Reminds me of doing a feasibility study that I wish I published regarding how well performing the COTS equivalent spec lamps were compared to the marked up bought out (higher quality spec?) name branded for the FT-NIR I was working with. Get's me wondering what headlights on the market meet suitable performance specs.? Reads an InGaAs detector is being used also and not the DTGS, PbS or InSb. I preferred the InGaAs TE cooled for all my FT-NIR work.
Subbed. I was just about to comment "where'd you get the pot" hhaha damnit.
:-D Thanks for the sub!
It'd probably be a good idea to check how much RF power a setup like this is radiating while it runs. Even a fairly small amount is likely to catch someone's attention when it's in and around Airband frequencies like this!
Very interesting device.
Great video! I'd be interested in what effect RF power has, I imagine it would affect frequency response more than vco frequency too given the direct dependence of the crystal compression with the amplitude. In your video you suggested changing the amplifier power rail, but that might cause compression and additional harmonics in your RF leading to more mixed response. A better approach might be to add an additional stage of amplification then an RF attenuator to control level. You can get VC RF attenuator boards on eBay too. Would be great to hear what you think.
Just as a small warning: if you want to actually tune your light, do not get an acousto-optic modulator! They're designed for much, *much* higher power, both RF and optical, usually starting around 15W and going up to 100W(continuous!), they _will_ need to be driven at that power to see an effect and the high power AOM drivers are very pricy. I'm on the high power side of the camp, using an AOM to q-switch a DPSS laser, and my 50W rated q-switch only started showing an effect at around 15W of input, operating correctly at around 30.
Interesting. Is it down to the size of the crystal and/or design power perhaps? I ask, since I have a millijoule Q-Switched YAG (Non working...yet). the physical size of the Q-Switch is quite small, maybe 20mm long and the diver itself doesn't seem too large either.
@@LesLaboratory I'm not actually sure, but it might be to do with the material and its damage threshold.
My crystal is pretty small too(G&H QS27 series), most of it is just the big water-cooled metal housing.
I'm sure it would disturb the q factor of the cavity at lower power, but I didn't see a significant splitting effect until around 15 when I was putting a red laser through it.
Used to work on DPSS systems largest amount of power (for the aom) we used was around 200W.
In the USA those warranty void stickers are illegal.
As it should be!
could you try to generate sound with light modulated by this AOM?
a triangle wave generator (at 100khz or so) fed into a comparator with a ordinary audio signal fed into the second port, out comes a variable pwm duty cycle (like a class-d amp)
with it you can turn on/off the AOM.
i found that shining a intense beam of light onto candle soot covered surface or any other black plastic / paint creates sound. it makes the changes in intensity audible.
also works with powerful leds. but its not very loud and not efficienct at all. not sure whats going on, maybe thermal effects.
imade 2 videos showing the effect a while ago. would be great to further investiage on this to maybe create a "Laser Tweeter" or something haha
I want to make a video about laser pews in space. There are a lot of people who go about saying that you would not hear things in space, however if a laser hit your space ship and was modulated you would have a chance of hearing a sound. It's a video I may do in winter.
Something else that could be done for what you are speaking of could be as easy as using say Audacity to shift the a sound wave entirely above the 0 crossing and use it to drive a transistor in parallel with his amplitude potentiometer. His AOFT is certainly capable of modulating a fair bit of power so he has a good chance of making some music happen.
Fantastic video really appreciated this as I have a Qswitch module and its driver and wondered how it was used. Unfortunately I have no datasheet on either as they have had any OEM info erased and only have a Rofin part number now. The modulator I have looks very similar to yours but is smaller and has 2 SMA connectors, one is obviously RF and connects to the driver but the other doesn't appear to be RF as its only twisted pair wires, I don't know if its an input or output but Im guessing its an output for some sort of monitoring, have you any ideas? I received a whole pile of optical stuff from a very fancy passport laser printer which generates holes through the passport. So its quite a grunty laser (40W) , more power than I'm willing to play with at my experience level or have a power source but I do have HeNe etc units so Im really looking forward to setting up an optical bench and having an experiment with optics. Thanks to your explanation about safety glasses I have ordered some reputable ones, when they arrive I should have a table ready to go Woo Hoo.
I hate when manufacturers do that! It does sound like some kind of feedback loop. do you have a picture? Nice! I had never considered passport printers for parts, interesting! :-)
Amazing!!! The guys a THORLABS should throw some money into the hat :P
Ha! I wish!
Is that a "filter" or a "modulator?" If it is a filter, can you put in white light and get a variable wavelength light out?
It's a tunable filter, so yes, if you collimate white light, and pass it through, it would be possible to pick off any wavelength. This technique is used in some types of Hyperspectral cameras, where a sequence of pictures is taken, whilst an AOTF sweeps across the spectrum.
Cool way to pulse a laser with sound.
Ohh this is amazing and beautiful experiment. I do have a question and I hope you see it to help me understand. So, I noticed that your first green laser(black enclosing) was CW laser but when you fed the AOM with function generator, apart from splitting of laser, you got a pulsed laser. Is it something also an effective way of pulsing a CW laser? So, for. e.g. can we use the VOC and AOM to produce modulation and pulse in a CW laser? Can we produced a 100 fs pulse?
Yes, effectively you can modulate the laser beam , thereby pulsing it. The problem with AOM's is you can't do this very quickly. The carrier frequency is about 100MHz, and the crystal has to physically oscillate when you apply the signal, all of which takes time.
There is no chance of getting 100fs pulses out of this setup, in fact, those kinds of speeds are only really achievable under special circumstances, for example with mode locked Ti:Sapphire Lasers, or by using non-linear optical magic with Mode locked Nd:YAG Lasers.
Great build....cheers.
Thanks!
Cool video - everything makes sense to me except the capacitor next to the power jack? What is that doing?
@@phuecn just a bit of smoothing. Some wall warts have noise and ripple.
@@LesLaboratory Ah, fair enough. I assume this can be run off of a small 12v PS? What amperage would you recommend? I've put together a parts list just now as my 30 year old AOM driver broke just yesterday!
Thank you for the informative video. What is the relationship between the frequency of signal generator and laser modulation frequency?
The higher the frequency, the shorter the wavelength of light it will switch. So for example at around 87MHz, it will modulate a red laser pointer at about 660nm, and at 101MHz with will modulate a green laser poiner at 532nm.
Awesome
Cool video, thanks :)
Hey Lees could u drive a 15 watt or greater Argon or Kypton laser. Use a greater crystals with sound to split 515 nm and 448 nm and the wavelength near purple? Does ur Argon still work? 15 years ago a 6 W gas tube on ebay was 60 grand!!
Amazing
I believe the screw pattern on the lid is different to make sure that you cannot put the lid on incorrect :D
Ha! So it is! :-S
Thank you so much for the helpful video. I am about to purchase an AOTF for our lab and am thinking about making a homemade driver. What is the difference between an AOM and an AOTF? Would it work to use an AOM in place of an AOTF if we just modulate the frequency of the input?
Cheers! AOTF's are designed to be able to control wavelength, and AOM's are just modulators. I guess the difference is in the physical packaging and the controller. I you just want to turn on and off the beam then AOM, if you want to select wavelength then AOTF.
@@LesLaboratory Got it, thanks!
impressive
So you can affect the pulse rate of a laser beam from as low as 1hz, to what mhz? How is the polarization controlled sir?
Interesting video. Wonder how the signal would be if the input was a photodiode.
The modulation signal?
@@LesLaboratory Yes, just curious if the actual light modulation would be as clean as the input. Looks like you were reading the input signal on your scope and visually assessing the output.
@@lambda4931 ah, right. Depends really on the application. I measured this recently for someone, and the carrier wave that drives the crystal is clearly visible in the output. For good clean on/off switching of a beam, a Pockels cell would be faster, better and cleaner.
I thought you were going to plug in some Led Zeppelin but learned something instead. ;)
Surely some Floyd as well ?
1:41 - "thats it, not very existing" lmao you can that again. I wonder what is the life span of these AOM devices, how long can I use them for before it needs some form of calibration since it seems like it uses some kind of springs? Can I use them for precision based photolithography? Thanks.
Indeed! I would say, probably indefinitely. There are no springs, its is basically just ultrasound though a rock. It depends in what context you anted to use it for photolithography. If it is for modulating the beam, then sure!
Thank you for the useful explanation! Basically this is a useful technique to modulate a CW laser. I would like to modulate a CW laser with 10Hz and a duty cycle of 99.9%. This means a pulse of 10us and 100ms Off time. I also tried this with a 'noise eater' from BEOC and a wave generator, but the nonlinear optics resp electronics from the 'noise eater' are too slow. A duty cycle of 99% with 10Hz is the edge. Do you think I could manage the 10Hz and 99.9% dc with your set-up in your video? Did you measure the shortest possible pulse?
Ah, Dan Maloney pinged me about this! You should have a message in your e-mail inbox, along with oscilloscope shots.
amazing!
Thanks!
On the AOTF, that's a regular SMA connector not an RP-SMA connector. As far as I've seen, RP-SMA is only used on consumer Wi-Fi equipment.
So it is! You are right.
I tried the same RF ampifier, but it was broken because of the over heating. Could you please suggest another one? Thanks.
For a specific applications i need up to 700 MHz of modulation frequency. do you think this is possible? i haven't seen any commercial products being able to produce such a frequency.
Not with acousto-optics. I think Pockels cells will go to 100MHz+ , for really fast speed, you might get close with a Kerr cell. What is the application?
The link for RF Power Amplifier Module is invalid. Could you please check and suggest similar products? Thanks!
Any 2w RF power amp that can amplify in the range 80-150MHz or so will do. Quick search pulls up this. Never tried this brand, but it will probably work: www.amazon.co.uk/1-930MHz-Amplifier-Module-Broadband-Transmission/dp/B076ZP8DB6
@@LesLaboratory thanks.!
Can you drive it with a square wave, was thinking of a Si535?
You mean just the AOTF? I would be inclined to build an RC network to convert that square wave into a sine wave. I suspect all sorts of nastiness would happen otherwise. You will need to amplify the output of the Si535 as well.
The coax connector looks like an SMA to me, not an RPSMA.
you are correct. RP are for wi-fi. That's what I get for not scripting.
Is there any GUI or any software that can be used to steer the beam?
Not that I know of, but it could be done with an Arduino and a DAC. Bear in mind a PCOM or AOTF doesn't steer the beam, more like select wavelengths. To efficiently steer, consider using galvos (check out some of my other videos)
@@LesLaboratory Thank you for your reply. Could you please refer to me a tutorial where the connectivity and control of the galvo system is explained? I am trying to learn about the system, but couldn't find a proper source.
It is not a standing wave, the acoustics is a traveling wave.