Drawing on a plasma display with a laser pointer

An orange plasma display will retain an image caused by incident near-UV light. This is an interesting visual combination of photoelectric, hot carrier injection, plasma, and charge trapping effects.

Correction: The orange display is running at 700Hz, 130V in the video. Also, the laser emits no 365nm light. I measured some as low as 380, but the tail isn't as long as I implied! Thanks Matthew King for pointing this out in the comments.

I realize that I may have conflated the issues of one-resistor-per-pixel and the display's ability to maintain an image throughout row scanning. They are separate problems that are both addressed by designing the panel to work on AC. Each pixel can maintain its state (on or off) by being supplied constantly with a lower "sustaining" voltage, and can be set or cleared by giving it a momentary higher or lower amplitude. The sustaining voltage allows the pixel to be emitting light or not, and its state remains because of its own impedance until updated on the next scan. In color plasma displays, separate electrodes are used for sustaining and addressing pixels, and the discharge may be sustained between coplanar electrodes instead of plane-to-plane, as in this display.

It's also a possibility that the dielectric and MgO layer only exists on one electrode (the metal), and the ITO is bare. I don't know.

On this display, if all rows are electrically connected together, and all columns are connected together, and AC is applied to rows and columns, this effect does not work -- no light is emitted at all! At least some of the electrodes (ie every other column) must be left floating to emit any light, and to show this memory effect. So, driving AC plasma panels requires more waveform tricks that I do not fully understand.

Applied Science video with rotating, flashing neon light:

Prior art patents:

Refs:

[rehoboth_farm]

When I worked for a large chip manufacturer who makes processors for computers... You know the guys. We just used SiO2 for the ILD, inter-layer dielectric, material which separated the layers of metal lines. So essentially just glass. I don't think it was any special recipe of any kind. I think that it is pretty standard semiconductor tech. We just used silane gas and oxygen at specific temperatures and mixtures to grow SiO2 if my memory serves correctly. Now, the chemistry to keep copper from diffusing into it and the techniques to get nice square bottomed etched lines was extremely sensitive and I don't believe that I can discuss that. Glass is a really easy to manufacture dielectric material with suitable properties. It also etches really easily and predictably with HF. It would seem that manufacturing panels like this would be very similar in process techniques.

[agentgreengnome]

During my first night flight while training for the my pilot's licensee, in the school's beater C172 from the 70's, the radio's orange display quit working when we needed to be changing and monitoring Air traffic frequencies. The radio still worked, we just couldn't see what channel we were on or what channel we'd be changing to. Having an unknown electrical issue in the air at night was pretty nerve racking, hoping it is not the beginning of a bigger systematic failure. Even the CFL was unable to troubleshoot the issue.

After a couple rounds of troubleshoooting and restarting the avionics to no avail, I shined my LED head lamp near by and the display lit up! I don't remember if the screen was refreshing properly, but I remember for the remainder of the flight, I'd have to "reignite" the display with the LED light every now and then.

I always wondered what the phenomena was, I always assumed the display was just barley being driven below some some energy state threshold and the LED photons gave it just enough kick to change states. I thought the display was an orange cold cathode, but maybe it was a plasma display as show in this vid.

Very cool video as always!

[Muonium]

Several things amaze/surprise me about this video. First, that you are able to come up with topics so consistently novel, fascinating, and non-intuitive that I never would've thought to investigate such things on my own if given about a thousand years to do so. Second, that people are still finding use for images that I uploaded to wikipedia 15 years ago, like that reflection microscope image of a Dell Axim PDA's TFT at 8:40 - this is greatly pleasing to me. Thirdly, that there is 365nm radiation coming out of 405nm laser diodes as you mentioned at 5:20. Can that be right? I've measured the spectrum of these cheap laser diodes before and while they're obviously not as clean and monochromatic as a gas laser, they're still way narrower than an LED and have a FWHM of only a couple nm - I'd like to hear more about this because I know you have a spectrometer too so I guess you've seen it firsthand. And fourthly, that nobody ever even knew about this throughout the entire heyday of the neon plasma display during the 80s and early 90s and no one ever made a product exploiting it! Anyway, you are my fav science youtube channel for many years now and I hope the new videos never end!

[account]

I don't think you need to worry about your video output schedule, we, your crowd, appreciate your "quality over quantity" approach...

[HuygensOptics]

Another reason for making the back electrode from metal (except price) is that metals are generally reflective and send additional light in the direction of the viewer. Anyway, superb video again Ben!

[rdyer]

Back in the 80s I worked with people like your colleague (and you). They invented a microwave chamber that heated a cup of coffee (not patented) a discrete-logic version of the Pong game (not patented) a laser-based digital data storage/retrieval device using a photographic plate and LASER (patented), which later became the basis of the CD-ROM. These were fun people, often a bit eccentric, but usually quite humble. The best job I ever had primarily because of the people!

[RingingResonance]

It might work similar to the old Tektronix storage tubes. They use flood guns to flood the whole screen with electrons, but the phosphor does not glow because it's not enough energy to excite the electrons until you get a more intense beam of electrons to "activate" the phosphors by giving them an extra charge so that the energy of the flood gun is enough to get the electrons over that charge state and produce light in that spot.

[williamgreen]

Funny you mentioned neon bulbs. I noticed the output of a neon bulb can be affected by the amount of ambient light.
I have a power on indicator neon on our boiler that's usually in a dark room, and it has a slight AC flicker to it. When I shine a light on it the flicker stops and its light constantly.

[daic]

7:26 Brings back memories of my childhood, first multimeter and a mains socket.. Hmmm, my meter has a 20 amp range.. This is a 13amp outlet.. Let's measure the current! Lesson learnt, multimeter fixed and socket replaced.

[CuriousMarc]

Interesting effect. Are you sure you are not just simply ionizing one of the UV lines of the argon or neon? One way to find out is to try it in a regular neon bulb. If you can strike it by shining the laser in-between the electrodes, it’s ionization, if it works inly by shining it on the metal, it’s photoemission. But if it were really photoemission, it would make more sense to me that it comes from the MgO, not from the ITO or metal layer buried under a dielectric. Just don’t see how you can have an electron current nearly high enough to strike a neon plasma coming through a dielectric. Just talking out of my rear-end since I have not researched the subject properly…

[ACBXEric]

Plasma TV sets have a property like this. If you look closely, generally only seen in a dark room, when turning it on, before the set starts making a picture, the screen will show a blotchy approximation of what was last displayed when powered off.

[hellterminator]

You actually can sort of get away with neon bulbs in parallel. Yes, initially, one will hog all the current, but over time (weeks to months, in my experience) it will degrade until they even out. But then, they won't light up all at once, no, instead, on each half-cycle, a random one will light up (and then a different one and then a different one). If you connect about a dozen of them in parallel, after the initial burn-in, they create a really nice dancing light effect.

[cashewABCD]

Glad I listened till the end, your intuitions are genius. The patent surprise is a fun twist. Thanks for another great discovery!

[stdorn]

I worked as a biomedical. equipment technician for 18 years and this was one of many devices I worked on. if memory serves me correctly this is from a Propaq Encore patient monitor. I wonder if I ever serviced the one this came out of.

[bronsonstephens]

Man. You continue to impress me with every video you upload.

[aronbjr]

This is part of the optogalvonic effect, in which the discharge changes it’s resistance due to incoming light. If you sweep a continuous spectrum of laser light (like from a dye laser), you can measure the resistance change of that gas filling the discharge. I used this as a calibration standard (neon lamp - also argon or other gasses that have emission spectra peaks at important calibration wavelengths), and as you tune / sweep the dye laser (in my case a grazing incidence R6G pulsed dye laser) thru the spectrum, when the due laser matches a peak emission of the gas, the resistance dips… and so you know the dye laser is at that exact frequency / spectrum. I would partially power the discharge lamp, and when the laser wavelength matched a strong emission peak, the lamp would light. There are a few other related phenomena to this, one used for deep space photography, by CCD deep-discharging using deep UV from the sun.

[cobralyoner]

there’s just nothing like the glow of these old plasma displays. miss them. they looked just so cool!

[PhillMcrackensGhost]

I can imagine a legendary crossover event with How to make Everything, Cody's lab, Nile Red, and Applied Science if HTME ever makes it to the modern era.

[Zanaki]

This is so cool, I wonder what the other comments think!

*I can't understand a word of what they think*

[interferon]

I sure am glad Ben takes the time to publish his endeavors so we can all enjoy them. Lots of people talk about theory, few make practical implementations.