Interference Patterns Harnessed For Optical Logic Gates

The basics of digital logic are pretty easy to master, and figuring out how the ones and zeroes flow through various kinds of gates is often an interesting exercise. Taking things down a level and breaking the component AND, OR, and NOR gates down to their underlying analog circuits adds some complexity, but the flow of electrons is still pretty understandable. Substitute all that for photons, though, and you’ll enter a strange world indeed.

At least that’s our take on [Jeroen Vleggaar]’s latest project, which is making logic gates from purely optical components. As he himself admits in the video below, this isn’t exactly unexplored territory, but his method, which uses constructive and destructive interference, seems not to have been used before. The basic “circuit” consists of a generator, a pair of diffraction patterns etched into a quartz plate, and an evaluator, which is basically a pinhole in another plate positioned to coincide with the common focal point of the generator patterns. An OR gate is formed when the two generators are hit with in-phase monochromatic light. Making the two inputs out of phase by 180° results in an XOR gate, as destructive interference between the two inputs prevents any light from making it out of the evaluator.

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[Ben Krasnow] Rolls Old School Camera Out For Photolithography

In a time when cameras have been reduced to microchips, it’s ironic that the old view camera, with its bellows and black cloth draped over the viewscreen for focusing, endures as an icon for photography. Such technology appears dated and with no application in the modern world, but as [Ben Krasnow] shows us, an old view camera is just the thing when you want to make homemade microchips. (Video, embedded below.)

Granted, the photolithography process [Ben] demonstrates in the video below is quite a bit upstream from the creation of chips. But mastering the process on a larger scale is a step on the way. The idea is to create a high-resolution photograph of a pattern — [Ben] chose both a test pattern and, in a nod to the season, an IRS tax form — that can be used as a mask. The camera he chose is a 4×5 view camera, the kind with lens and film connected by adjustable bellows. He found that modifications were needed to keep the film fixed at the focal plane, so he added a vacuum port to the film pack to suck the film flat. Developing film has always been magical, and watching the latent images appear on the film under the red light of the darkroom really brings us back — we can practically smell the vinegary stop solution.

[Ben] also steps through the rest of the photolithography process — spin coating glass slides with photoresist, making a contact print of the negative under UV light, developing the print, and sputtering it with titanium. It’s a fascinating process, and the fact that [Ben] mentions both garage chip-maker [Sam Zeloof] and [Justin Atkin] from the Thought Emporium means that three of our favorite YouTube mad scientists are collaborating. The possibilities are endless.

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Homemade Integrated Circuits Hack Chat

Join us on Wednesday, August 14th at noon Pacific for the Homemade Integrated Circuits Hack Chat with Sam Zeloof!

While most of us are content to buy the chips we need to build our projects, there’s a small group of hackers more interested in making the chips themselves. What it takes the big guys a billion-dollar fab to accomplish, these hobbyists are doing with second-hand equipment, chemicals found in roach killers and rust removers, and a lot of determination to do what no DIYer has done before.

Sam Zeloof is one of this dedicated band, and we’ve been following his progress for years. While he was still in high school, he turned the family garage into a physics lab and turned out his first simple diodes. Later came a MOSFET, and eventually the Z1, a dual-differential amp chip that is the first IC produced by a hobbyist using photolithography.

Sam just completed his first year at Carnegie-Mellon, and he’s agreed to take some precious summer vacation time to host the Hack Chat. Join us as we learn all about the Z1, find out what improvements he’s made to his process, and see what’s next for him both at college and in his own lab.

join-hack-chatOur Hack Chats are live community events in the Hack Chat group messaging. This week we’ll be sitting down on Wednesday, August 14 at 12:00 PM Pacific time. If time zones have got you down, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about.

Of Roach Killer And Rust Remover: Sam Zeloof’s Garage-Made Chips

A normal life in hacking, if there is such a thing, seems to follow a predictable trajectory, at least in terms of the physical space it occupies. We generally start small, working on a few simple projects on the kitchen table, or if we start young enough, perhaps on a desk in our childhood bedroom. Time passes, our skills increase, and with them the need for space. Soon we’re claiming an unused room or a corner of the basement. Skills build on skills, gear accumulates, and before you know it, the garage is no longer a place for cars but a place for pushing back the darkness of our own ignorance and expanding our horizons into parts unknown.

It appears that Sam Zeloof’s annexation of the family garage occurred fairly early in life, and to a level that’s hard to comprehend. Sam seems to have caught the hacking bug early, and by the time high school rolled around, he was building out a remarkably well-equipped semiconductor fabrication lab at home. Sam has been posting his progress regularly on his own blog and on Twitter, and he dropped by the 2018 Superconference to give everyone a lesson on semiconductor physics and how he became the first hobbyist to produce an integrated circuit using lithographic processes.

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Using Pad Printers To Add Color To Artistic PCBs

I’ve done a few experiments in adding color to printed circuit boards. These experiments used a process known as pad printing, and so far all indications are that pad printing is a viable process for truly multicolor artistic PCBs. For this year’s DEF CON, I’m stepping things up and taking them to their logical conclusion. I’m making true multicolor PCBs with orange and blue ink. This is, I believe, the first time this has ever been done with printed circuit board art, and it is certainly the first time it has ever been documented.

You may be wondering why I need more color on my boards. It’s that time of year again where PCB artisans all around the world are gearing up for badgecon DEF CON. For the last few years, independent badge makers have come together to form a demoscene of hardware creation. This year, add-ons for badges are a thing, and everyone is getting in on the game. Tindie is filled with amazing electronic badges and add-ons that will be found at this year’s DEF CON. There are badges featuring the Cromulon from Rick and Morty, baby Benders from Futurama, pikachus, and glowing tacos.

This is all about badge art, but when it comes to rendering an image in fiberglass and soldermask, everyone is working with a limited palette. Yes, you can get pink and orange soldermask, but I can’t find a place that will do it inexpensively. For any PCB, your choice of colors are only green, red, yellow, blue, purple, black, or white. No, you can’t mix them.

But I want both orange and blue, on the same board, cheaply and easily — here’s how I did it.

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LED Fabrication From Wafer To Light

Building a circuit to blink an LED is the hardware world’s version of the venerable “Hello, world!” program — it teaches you the basics in a friendly, approachable way. And the blinky light project remains a valuable teaching tool right up through the hardware wizard level, provided you build your own LEDs first.

For [emach1ne], the DIY LED was part of a Master’s degree course and began with a slice of epitaxial wafer that goes through cleaning, annealing, and acid etching steps in preparation for photolithography. While gingerly handling some expensive masks, [emach1ne] got to use some really cool tools and processes — mask aligners, plasma etchers, and electron beam vapor deposition. [emach1ne] details every step that led to a nursery of baby LEDs on the wafer, each of which was tested. Working arrays were cut from the wafer and mounted in a lead frame, bonded with gold wires, and fiat lux.

The whole thing must have been a great experience in modern fab methods, and [emach1ne] should feel lucky to have access to tools like these. But if you think you can’t build your own semiconductor fab, we beg to differ.

[via r/engineering]