Counting Atoms with the Doppler Effect - Heterodyne Interferometer

[@seeigecannon]

35 year old person who works in an R&D department designing/building all sorts of neat things: I hope to become as smart as you when I grow up.

[@UniquelyCaptivating]

lol why does he look 23

[@jaggar28]

@@UniquelyCaptivating He is probably around 21 years old.

[@ChrisHillASMR]

Power wheels design does not make one an engineer

[@seeigecannon]

@@ChrisHillASMR are you suggesting the guy who put together his own fab and is designing chips is not a real engineer? If not could you explain your comment?

[@xxCRODxx]

Esse cara é muito acima da média em questão de inteligência.

[@yum33333]

Hi, I'm a physicist/electrical engineer. That sound you hear may be the driver amplifier going into oscillation because of the capacitive piezo load. You can make it stop doing that by placing a resistor in series between the amplifier and the piezo, probably 50-100 ohms will suffice. Another possibility is that at certain outputs - i.e. the max or min output voltage of the amplifier - you may be exceeding it's rated common mode range. This may lead to oscillation, though this is completely dependent on the exact IC you are using. Finally, and this is very unlikely, but it is possible that for max/min output voltages a wire is shorting to the metal optical bench, producing a tiny arc that makes a buzzing noise. But I would be very surprised if this is the case. EDIT: Oh crap! Hi Sam! I just realized it's you! I'm the younger guy you met when you visited MIT to mess around with our electron microscope.

[@SamZeloof]

hey Colin! hope you are well. thanks for the note, I'm going to investigate that weird noise some more, I thought oscillation at first too but the driver has ample frequency compensation and can drive capacitive loads up to a few uF. I could me missing something though, we will see

[@edinfific2576]

You're overthinking it. Check the driving frequency, it's only 1Hz, if I see it correctly! The possible causes you describe normally happen at much higher frequencies. What I think is happening is a plain mechanical noise resulting from the crystal material being deformed and rubbing/pushing against its metal membranes, similar to the noise of a dry finger dragging across dry paper or a thin plastic or metallic surface. Chances are that this noise's frequency is related to the metallic surface size of the piezo disc.

[@chrismr3972]

@@SamZeloof Gain of 27 so there's a chance of feedback, maybe from a grounding issue. It's good practice to put the amplifier right next to the load because you also have quite a bit of inductance in your cables, but in this case the magnetic fields might cause small changes (wires etc can twitch) to mess up the measurements. The other way to do it is to take separate wires back from the piezo to the amplifier so you can correct for inductance / capacitance "at the sensor" - like a good LCR meter does using Kelvin probes. I spent many years in radio interferometry (direction finding) - working tiny signals using cross correlation which is fascinating. Great to see you doing this.

[@MadScientist267]

@@edinfific2576 Agreed. That's what it seemed like to me as well. Those discs have a very distinct timbre when they are buzzing against something... Sounded spot on to me

[@thevoidedwarranty]

I think it's just the pwm drive frequency because its not a pure linear driver chip

[@lordblackwood8459]

Finding small gems of channels like this. Is why I stick around on youtube.

[@2jpu524]

I've worked for a time developing femtosecond and picosecond lasers, and we did a trick that I think will help you out immensely -- Water cooling your baseplate with a chiller. The Mai Tai laser that Spectra Physics makes has a copper tube that is pressed into the aluminum plate that's connected to a temperature controlled chiller. This trick was also useful to temperature stabilize our power meter as well. Making a box around the thing will also help a lot. You can make something out of clear plexiglass to isolate it all from air currents. Just blowing air inside the resonator path of a Ti:sapphire femtosecond laser was enough to get it to stop modelocking. There are tones of simple tricks you can do so you can focus on what you want to use it for rather than watching it drift. You can also consider things like using dry nitrogen inside your box to control the relative humidity, etc; or at the very least some sort of desiccant that changes color as it absorbs water so you know when to heat it up a gain to drive off the moisture. Good luck. You have an awesome set-up.

[@sparkyy0007]

You can thermally compensate your optical bench (similar to a xtal oven freq stabilization) to +- 0.1 deg C with a DIY full area heater constructed of a large PCB panel under the optical bench. Etch the copper heater trace pattern to cover the entire panel and use a current source with a temp feedback loop (K thermocouple) to a pid controller. 1 ohm heater trace resistance at 5 A gives 25 watts, more than enough power to bring your optical bench 5 C above ambient and thermally stabilize the optical bench. Awesome metrology demo !

[@genericalias5756]

it's been two years, but would you be concerned about convective air currents causing minute displacements?

[@Alexander_Sannikov]

Gosh this is really good one. Videos on this channel don't come out often, but when they do, it's amazing.

[@christopherleubner6633]

Remember grabbing those HP lasers up and fixing them, it isnt too difficult, just adjust the HVPS for optimal emission then once warmed up adjust the pezio inside until you get a stable locking frequency. What you are aiming for is a couple stable modes separated by a few MHz. Then your laser can be used for vibrometry like this. Believe it or not these HP lasers were used for active vibration cancellation on semiconductor fab machines. You can use a regular polarized hene laser with s heater and a couple magnets with a window controlled by a pezio disk to make one. Melles Griot part number LLR-1P was particularly good. ❤

[@w2aew]

Really cool stuff, Sam! Very impressive!

[@markTheWoodlands]

Sam, Great example of all the environmental factors that a good experimental scientist has to consider and adjust for. It is really fun to watch metrology that approaches single atom precision. When you showed the graph of your lab temperature over a 24 hour period it reminded me of how Henry Ford and other early industrialists tried to keep the measurement areas of their factories within a narrow range so their gauge blocks would be accurate to within defined tolerances.

[@MadScientist267]

Way underrated channel man. Very informative.

[@KonradTheWizzard]

Since you asked: semiconductor equipment keeps its precision by a few methods combined. One: the area they stand on is physically uncoupled from the floor you walk on - it stands on the same foundation (or actually the same very heavy and large concrete beams on the 3rd floor of the building), but has its own very sturdy connection to it. To make it more "fractal": the entire building is also uncoupled from surrounding streets (and the parking lot) by driving the foundations very deep into the ground. Two: the more sensitive the equipment, the larger the very heavy slab of granite in the bottom of the machine. Large mass means it picks up less vibration - or more precisely the same vibration energy has to move more mass, which means less amplitude for the same energy. Three: cleanrooms are controlled for temperature, pressure and humidity (apart from particle count of course). I like going in there - no matter what the wheather is like outside it is always a very nice temperature and humidity and the pressure doesn't swing as badly as the outside (or even the office) even during a thunderstorm. So I'd recommend: make sure you have the instrument on a very sturdy table. Add some very thick felt to absorb high frequency vibration. Then get a really large piece of polished granite from the home improvement store (or a local funeral director - sometimes gravestones are discarded without being used) and place it on top. Then place the equipment on the stone. I would recommend you do the same for your stepper.

[@jcims]

This is a pretty incredible demonstration. Nicely done!!! I wonder if you could you feed the output to an audio amplifier and listen to it? Might be interesting to see if you can figure out what's introducing the various bits of noise.

[@SamZeloof]

i FFT'd the output and most of the noise is around 150hz, coming from fans inside the instruments on my bench. next largest peak is 60hz from the vibrations and hum coming from the transformers in those instruments.

[@jcims]

@@SamZeloof So no top secret conversations showing up from vibrations in the floor? :) Quick question, sorry if I missed it. If this is sorta superheterdyne, are A and delta A considered the baseband and B the IF? So you get a 1.5MHz tone plus a modulated 1.5MHz +/- relative velocity/wavelength? And this is what is counted in the software/scope?

[@RoadRunnerMeep]

Why is it always the amazing channels like yours have so few subscribers compared to the bigger ones. People seem more interested in boring clickbait, than actual education.

[@karlharvymarx2650]

Thanks for giving me lab envy. I have had a project in mind that involves measuring small displacements outdoors and I was wondering if you have inexpensive suggestions.I live on a mountain and could swear the angle of the trees to the ground is always changing. I suspect the top layer of land is gradually sliding down the mountain, but maybe wind is just shifting the root balls in the clay soil. I want to try to make a continuous measurement of the distance between (say 100m) points on the land. This interferometer seems like it might be the wrong tool for that job. Would something else, hopefully much cheaper and more rugged, be a better fit? Eventually I want to make a mudslide early warning detector because i'd really hate to wake up buried in mud and I'm sure many others feel the same way.

[@AJMansfield1]

You might want to consider using RTK-compensated GPS for this, as it allows distances at the scale you're interested in to be measured reliably without some of the limitations of this type of optical interferometry. Normally GPS is only accurate down to around 5 meters, but with RTK you can actually measure the distance between two receivers with an accuracy down to 1 cm +/- 2ppm. (In a sense, RTK _is_ actually a type of interferometry, using phase differences in the signals from GPS satellites.)

[@subirbhaduri]

Similar interest here. Can we make an instrument to detect potential landslides? I am from India and we are facing unprecedented natural calamities from heavy cloud bursts and accompanying landslides. Keen to know more if you have any progress on this front. thanks.

[@thatoneguy99100]

I'm very impressed with your setup! As you are no doubt aware you can greatly improve your vibration damping by building on a honeycomb core floated optical table, of course at a greatly increased price...

[@topphemlig1191]

Absolutely brilliant! In my dreams I'd like to be half as smart as you, what a demonstration of initiative and knowledge

[@daliborfarny]

It is exciting to see you making more videos! What is the background of your experiments - do work on some particular project or just having fun with all these exciting things?

[@SamZeloof]

thanks! i always look forward to watching your videos too, i've been considering doing an " art of making chips" vid like your famous one for a while now... I bought pretty much all of the equipment with specific goals in mind, i am mainly interested in making new tools for nanofabrication at the moment. but of course i get to have a lot of fun along the way with lasers and microscopes

[@daliborfarny]

Sam Zeloof wonderful, I actually found your channel by the “chips basics” videos. Cant wait to see more of your work!

[@kennethbeal]

Just watched your latest, Z2, and am really enjoying your older videos! Nice lab, and great explanation of the factors that can impact that precise measuring device!

[@Carsten_Hoett]

That was a really cool explanation and I finished my B.Sc. in 2015, so I started in 2012, which is 10years ago and I also applied once as a sort of techniquen for those kind of instrument, but this explanation reminded me at a interference labs exercise but actually the complete background of high precision measurement was lacking. This was a really cool "refresher" and gave also additional information to the measurements equipment. It is also quite clever to polarize the wave, chance them in the phase so that they destrucet and end with the delta valve.

[@upoupil4012]

most amazing youtube channel for scientist.....

[@DStageGarage]

Years back I was a Phd student (never finished for various reasons :p) and we were working on a bit similar thing but instead of two beams we had three that created lattice of optical vortices captured on camera, in theory could be 3 orders of magnitude better than traditional optical microscopes (since you got the picture of an area it wasn't measuring just one distance but rather a whole area at one without any scanning). Well, that was still a theory back then ;-) Anyway, the lab was at third floor (don't ask why i was not in the basement :p) and you could see people walking on the corridor not to mention trams near by. For that reason we were often doing stuff at night heh.

[@fabianforslund4622]

I may be wrong, but I noticed at 3:10 the graph seems to pick up the vibrations coming from your voice. A quite stupid but fun idea could be to put your head or a speaker against the table and see if you can pick up your voice more clearly.

[@CristiNeagu]

15:55 "That's all i have", he says... understating much?

[@HaydenHatTrick]

This is great motivation to get uploading videos about my own equipment. I have a similar addiction. That said, it would make your videos more palpable if you had some B-roll in your video, even just a moment of "I feel like making an interferometer". I get that B-roll is a little embarrassing (even just to have it sit on the computer), but seeing a little bit of set up and troubleshooting would add something to the video.

[@AlJay0032]

Wow, mind blown. Your setup is really amazing.

[@a3b36a04]

"We are at home with surplus parts from ebay." More high-tech equipment in background than several universities i know have combined.

[@jafinch78]

Thanks Sam! Excellent system presented without a doubt. Left me surprised regarding the price point, at first wondering about sensing for correction algorithms/feedback and finally also wondering what all signals emitted from your body and elsewhere you were able to observe specifically? I so want to make one even more ghetto cost effective. Then again, I'm still amazed at the price point for the whole kit using HP equipment. Thanks for sharing!

[@SamZeloof]

glad you enjoyed!

[@jafinch78]

@@SamZeloof This video just came to mind to use for a range of spectroscopic studies, i.e. LIBS, RAMAN and UV-Vis-IR and even wider frequency range spectroscopic studies or signals receiving. Any thoughts that are cost effective that come to mind? Thanks in advance for your time... really awesome inspiration.

[@squeakytoyrecords1702]

Very cool, Sam!! I'm currently working on an interferometer using a self mixing diode so I can avoid needing an extensive setup such as yours. Have you done any work with self mixing diodes? You just got a new sub, thank you for your work.

[@subirbhaduri]

I would be very interested in your experiments! I have a similar aim of using self-mixing diode setups, but the end-use is to detect environmental seismic vibrations caused due to human construction activities around forests.

[@guilldea]

So glad I found your channel

[@horus4862]

That was crazy good. I can't believe how amazing your set up is. I was wondering what would happen if you put the whole thing in a vacuum chamber and as close to zero you could get. Would cold and air pressure improve the accuracy?

[@tanchienhao]

i have bought a keysight 10780C receiver but i can't seem to find any pinout for the "strange unobtanium 4-pin BNC" -samlaser connector for it. Any ideas? I do know it takes 15V from the keysight datasheet though

[@ExtractionsAndIre]

Very cool!

[@MichaelRuwurm]

Hi, any chance we get a glimpse inside the piezo driver circuit box? Self made or eval module? Really enjoy your videos!

[@among-us-99999]

So, could you use this+some (maybe piezo?) actuators to map the surface of something?

[@leonardocorti1919]

Do you have some good papers/books to suggest about this topic?

[@JonnyDeRico]

repairfaq.org/sam/lasersam.htm

[@hinz1]

Holy shit, fully working HP 5528A. Must be quite some work to get such a thing from ebay back to work. Old electronics/test gear from ebay, usually not much problem. But anything with physics or optics inside is usually pure horror, from my experience. That thing is also extremely nice to check surface plate flatness, btw.

[@eberseth]

It is a 5517D or C laser head

[@Alexander_Sannikov]

i had to watch this video again two months later because felt bad that I forgot some details of how exactly this interferometer measures the frequency shift.

[@zyxwvutsrqponmlkh]

*Proceeds to install interferometer on manual mill as DRO* But seriously, I want to use a DLP projector to lithograph some silicon wafers.

[@armoryindustrial7884]

This is a truly wonderful video. Thank you for posting.

[@movax20h]

Use it as a microphone. It can probably detect vibrations in air, either moving the mirror, or changing the refractive index of the air.

[@gsuberland]

To improve thermal stability, could you use a resistive heater and thermocouple, thermally bonded to the optical bench, potentially with a PID for control? Or is the existing DHT22 compensation about as accurate as you can get in this kind of setup?

[@WaynesStrangeBrain]

I love the idea of using one of these systems to measure nanometers from meters or further away. But what I thought was really interesting is when you said that the temperature change "over a few cms" caused microns of drift. That drift should add up, no?

[@seditt5146]

I an working on something different but some modification may help any issues with noise. I am finding noise decrease in a stable system if you vibrate it from the vibrating objects frame of reference parasitic vibrations decrease. You're working with much higher resolution than I am but perhaps you could use such information to intentionally vibrate your entire system to gain stability. Remember if an object is vibrating tangential to the force of gravity at 60 HZ then 30 times a second the object is in freefall and essentially microgravity. Unfortunately also 30 times a second its at 2G give or take. Sure its much more complex than that but hopefully everyone gets the point. Its why a washing machine will walk itself to the point of lowest most stable node in forces.

[@shijiechai9780]

SO this is the absolute displacement measurement, not the distance measurement? I mean it can measure the object move from A to B precisely, but not the position A and B with respect to the reference? Could you please explain this?

[@djricky89999]

What are the tools to test an IC chip that doesn't cost too much ? And then this tool captures the chip design in CAD ?

[@widget_wizard]

Your videos are fantastic! You've got a new subscriber. Do you have a build log / rough price for building your Heterodyne Interferometer?

[@klab3929]

wooo more uploads :) keep it up keeps my brain trimmed

[@v44n7]

I just found your channel! I amazing! greetings from Argentina

[@SamZeloof]

thank you elon very cool

[@far1002]

Is the laser head missing something ? Is that a fan mount at the front. Was it removed for noise ?

[@eberseth]

The port on the side is for thermal regulation of the laser head.

[@asloobmudassar6869]

This is not a Laser Ruler because it does not give absolute measurement. Only relative measurements can be obtained. Moreover due to being highly sensitive to environment it cannot be used practically and thus nano meter precision cannot be obtained. It can only be used to demonstrate the basic concept of light heterodyning. The given system can only be used to measure relative velocity.

[@CanYTrespectMyPrivacy]

Cool stuff. Notice you are at ECE of CMU?

[@amessman]

Where would one find a plate with threaded holes like the one everything's setup on?

[@iIiWARHEADiIi]

Look for breadboard optical table or plate

[@khoanguyen5805]

Thank you for sharing your knowleadge !!

[@xDevscom_EE]

Nice video! That is one rusty BNC cable. I'd like to hear a story about it, why it's still in use, instead of a dumpster ? :D Do you have your Python apps hosted somewhere, to try something with data presentation on my own? I've used matplotlib a lot for passive analysis, but your live plots look must better.

[@SamZeloof]

Its all just on matplotlib locally on a desktop, matplotlib has decent animation functions for live plotting.

[@byronwatkins2565]

It is likely that the laser performs as specified (and better); however, it generates heat and causes the aluminum optical breadboard to expand. Stainless steel optical tables perform better, but aluminum foil shielding to redirect the heat would probably help... don't obstruct the cooling vents. The heterodyning wasn't explained well nor was the fact that the two waveforms were shifting during your discussion. The two red lines were separated by 1.58 MHz (about 200 meters) and you were clearly interested in smaller distances. I suspect that the piezoelectric induced modulation is important, but I don't even know what frequency you were using.

[@bernard2735]

That doesn’t appear to be an optical bench, is it substantial enough to isolate the interferometer? Also, how does it handle the vibration from all of that gear you have. By the way, cool video & lab :-)

[@proskub5039]

Sam's Laser FAQ! Now there's a name I haven't heard in a long time..

[@ЮжныйКот-м2э]

1:00 Почему микрометр градуирован в миллиметрах, у вас же дюймовая система?

[@edinfific2576]

У них дюймовая система, но научная работа ведется в международных метрических единицах. И они хотят везде перейти на метрическую систему, но она идет очень медленно.

[@MooreAnalytical]

Man your equipment is awesome. Do you work on equipment like this for a living? I run my own lab and I may have you repair some stuff for me haha.

[@friskydingo5370]

Amazing project 👌 👏

[@jfchebly]

This is sick! Good job man, my respect.

[@payanggabang]

What if software error ?

[@molekulaTV]

You re the one making chips at home right? You are really really talented!!!!!

[@molekulaTV]

By the way: figuring out quantum entanglement communication is gonna be your job. You re the one!

[@FesixGermany]

Finally I got to see this, just awesome.

[@beautifulsmall]

Visual basic GUI ? Nice work. PyQt5 for me, great data visualization and no doubt logging.

[@marwinthedja5450]

Okay, now I'm waiting for some experiments on the Casimir effect ;)

[@gamerpaddy]

bala cynwyd is an actual town in PA en.wikipedia.org/wiki/Bala_Cynwyd,_Pennsylvania

[@DC177E]

Fantastic work, great video.

[@far1002]

I think the interference is coming from the table one of the legs isn’t the same size ..

[@mateusmachadofotografia8554]

Amazing! Can you detect gravitational waves at home?

[@natalie5947]

This was legitimately fucking awesome.

[@MrShaun1578]

Try putting it on a granite surface plate and better yet put the granite surface plate On a thim rubber mat then put the interferometer on the granite surface plate. Between the rubber mat and the sheer mass of the granite it should mitigate even more vibration

[@jingruzhang452]

Invar alloy 是不是比 花岗岩 大理石 膨胀系数更低

[@milesprower6641]

You should convert the vibrations to amplified sound owo

[@terryglenweaver]

Ok, gimme a small bowl of atoms to count. Can I use chop sticks?

[@risesinner]

Great content!! I would love to learn more from you.

[@michaelpang4381]

When you use hot glue on the most delicate part of the setup hahahaha

[@SamZeloof]

not good

[@HamguyBacon]

you need a table with spring or levitate it with magnets.

[@sanmvegs1641]

He is 21 and measuring distance in nanometres and here I still struggles with vernier callipers

[@qijia4769]

Great video!

[@ferrocell_usa]

what's labeled an interferometer looks simply like a beam splitter

[@bluedart7663]

very good 👍👍

[@monchosoad]

This is amazing!

[@ozdemirsalik]

Maybe you should apply to ASML. They need bright minds these days. Moore’s law seems like ended this year.

[@karolsadurski1013]

Wow ur so smart man.....great job.

[@Mr0hreo]

THATS DOPE AS FUUUUUUCCCCC

[@kylesimukka]

Thanks for sharing!

[@miketoreno4969]

Nice work

[@markp5726]

You've probably solved any temperature issues that matter in the 2 years since this video, but just in case... High precision machine tools often pump coolant through the machine frame. I was going to suggest that as a way to reduce temp fluctuations of your optics table, then realized it'd introduce vibration of its own :D Switching to in-floor heating and cooling would help with the temperature spikes from the AC turning on and off, and simply leaving the AC's fan on all the time would probably help some.

[@kalpeshwani8520]

F1,F2, ∆∆ phenomenon.........similar to water falling from faceut distrubed at bottom reflects ∆f at top ......

[@kmbn75]

You is genius

[@บังมิด-ง8ณ]

Is there a way stop v2k !!!!!???

[@gamalielcambara969]

I wish I could afford to have these Instruments at home .. not cheap at all.

[@mariuspascu438]

Hi! your setup is not suited for such measurements: the wood table has a wide "vibrating frequency" suitable for musical instruments. That table does look like paper and covered with stickers, is not even wood. Try to put your equipment directly on the concrete in a basement.

[@ChrisVanderMerwe617]

Warning: Do not watch when intoxicated in any way shape or form 8-)

[@xxCRODxx]

You need a supercomputer to make supercomputer's

[@Juxtaposed1Nmotion]

you get a sub

[@hullinstruments]

Watching your channel makes me realize how much I hate my life and genetics

[@annoorkhan4219]

Hi

[@chiragsharma5050]

Man you much money this lab cost you