TNP #33 - OmniChrome Helium-Cadmium (HeCd) 442nm Laser Teardown, Theory & Experiments 

Bug Report: FLUKE 233 magical multimeter is clipping through objects again.

Another step on the long road to Signal Path lithography. We know what the chip logo will be.

14:16 The sudden horror of a decapitated multimeter head never fails to appall!

Thanks for still doing these vids they are often far too advanced for me but your delivery makes me understand a little more each time. Keep it up!

Fascinating! I've never worked with optics but recently got to see some operating optical clocks. Have you ever thought of doing a teardown and demo of an atomic clock? Watching the PLL lock in a rubidium module might be interesting.

Great addition to the channel. From microwave to nanowave!

The helium reservoir on the ones I’ve seen has a membrane that has increasing helium permeability as it’s temperature is increased. The heat sink band stops the heat conduction along the glass, so that the helium leakage is near zero. Incidentally, if a laser has been sitting too long, the helium pressure may be too high to achieve lasting until the tube has been run for possibly as much as 100-200 hours. And for the benefit of anyone who hasn’t already read a service manual on a helium cadmium laser, the discharge current is typically 100mA or more DC, with significant amounts of capacitance in the power supply. Accidents are likely somewhere between extremely painful and potentially deadly, from muscle contractions or heart stoppage. If you’re really lucky, you’ll only realize your heart stopped when it starts beating again and you just used up one of your nine lives. Or maybe that’s just what happens when voltage jumps without a direct contact with a HV lead.

This might have been the first time I've heard emission line spectra described as "tones". But I get it! I have a H-𝛼 emission line filter in the filter wheel of my CCD camera I use for astrophotography. It produces some very nice images of emission nebula. Turns out there's a lot of hot hydrogen in the Universe!

Beautiful! I have seen a couple of these pop up en eBay, but minus the power supply. So nice to see one up and running!

Gotta love seeing the spectral pairs.

Definitely like the variety of vids! As usual you show way more of the workings of these pieces of equipment than other channels, that makes it always interesting to watch.

Love it! I've been reading a few books on laser physics so this came at a perfect time.

Very cool and unusual laser, thanks for sharing it with us!

Very cool indeed. It reminds me my studies and specifically the lab time we spent building a HeNe laser "from scratch".

Nice! Really enjoyed this one!

I got into lasers on a hobby level with some HeNe tubes and not much later with an Argon Ion head and homemade power supply. But those transparent "glass" tube laser are always much nicer to watch ;)

Awesome work many thanks 🙏🏼

What a beautiful machine, thank you

Awesome topic !....cheers.

Very illuminating!

Helium/Cadmium? Never heard before - thanks! Once upon a time I got a HeNe laser for measuring the angle of a worn out steel blade used in making soft tissue in a paper machine. The blade was about 1 mm in thickness and the edge was worn an polished maybe 0.1 to 0.3 mm size. The laser had 1.5 mm beam, so some of the beam passed on eatch side of the blade, when aligned. At that orientation the worn surface reflected light at an angle, which I calculated by arctan function from the dot on a graph paper. The reason for my angle measurements was that also the machine slightly barrel shaped cylinder wore out unevenly and the blade wear angle variation along the nearly 5 meter length of the blade gave a map of the cylinder wear. Some time later my boss got new glasses, which he found some way wrong. He suspected a mistake in the pupil distance and asked if I could somehow measure it from the lenses. He knew what his pupil distance had been "for ever". I found that both 18:41 the glass surfaces produced a reflection and they matched, and also reflected back to the laser aperture only when at the desired pupil spots. Marking them with ink, it was easy to to measure the distance and confirm his suspicion. He went back to the optician, who was surprised that the distance had been correctly measured without an optician's tool. A "feather to my hat". Some time later I was involved with a test whether the paper dryness could be measured in line with an experimental Water Vapor laser. Despite a good theory, the desired 5 meter distance quickly turned beyond reach. Our test setup was only about 1 meter and already was too challenging. At the time there were commercial infrared based paper web moisture measuring devices, but they required complex mechanisms on two sides of the paper web, source and receiver traveling in a synchronized way. Consequently, they were deemed too cumbersome in use, and also too expensive. That is why the idea of a water vapor laser was tried.

I remember working with helium cadmium lasers back in the 1970s at Intec corporation. We used them to test certain types of photographic film without exposing the film.

I would love to see more laser and optics videos!

Love this video, more lasers please!!!

Great Video Thanks.

Amazing!

Another incredible breath of knowledge with a side of nerdgasm 🍻

I have loved lasers since we got to experiment with a very low power HeNe laser when I was in 8th grade (a VERY long time ago). That looks like a very capable spectrometer. I have always been fascinated by how 19th century scientists doing some fairly crude spectroscopy produced results that led us to understand so much about the structure of the atom and, on a different branch of the scientific tree, to the beginnings of quantum mechanics. I encourage you to explore more fundamental science topics!

0:33 "dumpster find", yea your dumpster is not the same as mine.. for sure.

Just brilliant.

Thank you

Thanks for another good and informative video! Those Omron hour counters lose their count when the internal battery dies, so they're not always accurate.

Big burney lasers always get my attention, never seen this type before. Big Thumbs Up 👍👍

Had a rodenstock laser lens calibration machine back then from the scrapyard, luckily it tripped the breaker before anything worse happened.. ^^

Im firing with my lazooor! Nice video!

Thats a heck of a laser pointer to keep your cat entertained!!☺☺😎

@TheSignalPath i completely agree, never take lasers lightly, darkly yes but not lightly. 😉

Incredibly cool laser and a great explenation. Could you maybe do a breakdown of the power supply? It would be interesting to see how all the current regulation and the controls work.

Would be nice to follow-up with a measurement of the narrowband laser spectrum and the coherence length of the laser..

The three metal rods that form the structure are made of a highly specialized alloy with extremally low thermal expansion.

Curious as to what the Optical Power output of the Laser is?

That was fun.

I think the connectors are MIL-DTL-5015. On the back of the case, the left most connector looks like insert 22-20, the middle one is 24-5, and the last one is 24-22. Maybe. Is the keying rotated? You can get MIL-DTL-5015 connectors on Mouser, though for whatever reason the pictures of circular connectors are always wrong.

These lasers are extremely tricky to operate. Each laser head has to married with the power supply. To retune a head to a new power supply you have to run it to heat up properly and then adjust the the cadmium and helium heater to get the correct pressure and gas mix. The filaments burning out are usually due to a current regulation fault in the power supply. ❤

great -- very interesting video again, never saw a he cd laser in action. I use laser in my profession usually semiconductor, also for spectrum analysis, I have a helium neon laser for experiments and reference -- @the signal path : which spectrometer have you used ? - I myself have a thorlab spectrometer CCS200 (200nm-1000nm) your seem to have a larger range !

Really enjoy these photonics videos. 🤌

Please use some polarizing lens to demonstrate Bell's theorem.

It threw me off at first seeing the laser spot through the goggles with a rated attenuation of 10^9 at the wavelength being emitted. I'd guess the light seen is not the emitted ~400nm light but instead longer wavelengths generated by fluorescence of the paper.

Do you have any thoughts on optical transconductance varistors and their applicability to microwave transmitters?

That is gorgeous all right. Was it out of something or is it some sort of lab optical source?

Are those cadmium deposits on the working laser inside of the tube meant to be there or was that due to improper shutdown sequence? and how do you know if hasn't negatively affected the mirror on the front of the laser tube?

It would be nice if you could disassemble the broken unit. I'm very interested how the helium storage and release mechanism is looking / working. First time seeing something like that for a nobel gas.

Brilliant, thanks 👍

Could you make video on phase array radar too ?

Wowsers what dumpster are you looking through?

Hi. What spectrometer are you using?

FIX MOAR TEST EQUIPMENT!!! J/k - this is really interesting.

I had a friend of mine who got killed at home by stepping on a laser cable part of his home laser setup - he was in his 20ies.

I have a question, when you examine the incoherent light in the chamber with the spectrometer what you see are the spectra lines of helium or you see also spectra lines of cadmium?

I see people repairing CRTs from vintage TVs. Maybe there is hope for the broken laser. Although cadmium isn't exactly friendly to play with.

I might have missed it, but what's the rated input and output power of this unit?

So what are these lasers used for ?

As Spock would say…..fascinating 🧐

Is the helium or cadmium being consumed when the laser is operating?

Can the glass experience a catastrophic failure?

I would've thought that laser was much older than 1996.

Near the start of this video you say that “if you only were to use helium and make a helium laser, you would get wavelengths at 632 nm or so which depends on the helium atomic structure.” I think that the 632 nm wavelength is associated with a helium-neon laser. The light from a He-Ne laser is from some of the neon atoms that radiate at 632 nm. The light is from neon not helium.

So what makes cd go its own place?

👍🙏❤

The reason you can see the spot with the OD9 goggles is because of the fluorescence wavelengths.

Not a fan of HeCd lasers... which were developed over 50 years ago. You can see by looking at it: they're very expensive. Supposedly Melles Griot still produces them (or at least sells them)... and some old photolith processes need them. I think newer, more robust, and affordable technologies have almost completely replaced them.

Where is the the rest body of the multimeter ? :D

What were these lasers used for?

Very neat! We have a coherent source of light lasing at a specific wavelength. What is this light source used for exactly in it’s time period? I’ve heard of lasers dubbed as a solution looking for a problem…what applications does this particular unit used for?

LED luminous coating produces visible light and semiconductor produce UV

I've watched like 1 minute of the video and I'm guessing it's a helium laser that fires up and heats the cadmium enough to get that part of the process started... probably not...but am I close even?