Author: Al Williams

4352 Articles

The Random Laser

January 15, 2026 by 4 Comments

When we first heard the term “random laser,” we did a double-take. After all, most ordinary sources of light are random. One defining characteristic of a traditional laser is that it emits coherent light. By coherent, in this context, that usually includes temporal coherence and spatial coherence. It is anything but random. It turns out, though, that random laser is a bit of a misnomer. The random part of the name refers to how the device generates the laser emission. It is true that random lasers may produce output that is not coherent over long time scales or between different emission points, but individually, the outputs are coherent. In other words, locally coherent, but not always globally so.

That is to say that a random laser might emit light from four different areas for a few brief moments. A particular emission will be coherent. But not all the areas may be coherent with respect to each other. The same thing happens over time. The output now may not be coherent with the output in a few seconds.

Baseline

A conventional laser works by forming a mirrored cavity, including a mirror that is only partially reflective. Pumping energy into the gain medium — the gas, semiconductor, or whatever — produces more photons that further stimulate emission. Only cavity modes that satisfy the design resonance conditions and experience gain persist, allowing them to escape through the partially reflecting mirror.

The laser generates many photons, but the cavity and gain medium favor only a narrow set of modes. This results in a beam that is of a very narrow band of frequencies, and the photons are highly collimated. Sure, they can spread over a long distance, but they don’t spread out in all directions like an ordinary light source. Continue reading “The Random Laser” →

Windows? Linux? Browser? Same Executable

January 15, 2026 by 22 Comments

We’ve been aware of projects like Cosmopolitan that allow you to crank out a single executable that will run on different operating systems. [Kamila] noticed that the idea was sound, but that the executables were large and there were some limitations. So she produced a 13K file that will run under Windows, Linux, or even in a Web browser. The program itself is a simple snake game.

There seems to be little sharing between the three versions. Instead, each version is compressed and stitched together so that each platform sees what it wants to see. To accommodate Windows, the file has to start with a PE header. However, there is enough flexibility in the header that part of the stub forms a valid shell script that skips over the Windows code when running under Linux.

So, essentially, Windows skips the “garbage” in the header, which is the part that makes Linux skip the “garbage” in the front of the file.

That leaves the browser. Browsers will throw away everything before an <HTML> tag, so that’s the easy part.

Should you do this? Probably not. But if you needed to make this happen, this is a clear template for how to do it. If you want to go back to [Kamila’s] inspiration, we’ve covered Cosmopolitan and its APE format before.

Philips Kid’s Kit Revisited

January 14, 2026 by 12 Comments

[Anthony Francis-Jones], like us, has a soft spot for the educational electronic kits from days gone by. In a recent video you can see below, he shows the insides of a Philips EE08 two-transistor radio kit. This is the same kit he built a few months ago (see the second video, below).

Electronics sure look different these days. No surface mount here or even printed circuit boards. The kit had paper cards to guide the construction since the kit could be made into different circuits.

Continue reading “Philips Kid’s Kit Revisited” →

Clone Wars: IBM Edition

January 14, 2026 by 47 Comments

If you search the Internet for “Clone Wars,” you’ll get a lot of Star Wars-related pages. But the original Clone Wars took place a long time ago in a galaxy much nearer to ours, and it has a lot to do with the computer you are probably using right now to read this. (Well, unless it is a Mac, something ARM-based, or an old retro-rig. I did say probably!)

IBM is a name that, for many years, was synonymous with computers, especially big mainframe computers. However, it didn’t start out that way. IBM originally made mechanical calculators and tabulating machines. That changed in 1952 with the IBM 701, IBM’s first computer that you’d recognize as a computer.

If you weren’t there, it is hard to understand how IBM dominated the computer market in the 1960s and 1970s. Sure, there were others like Univac, Honeywell, and Burroughs. But especially in the United States, IBM was the biggest fish in the pond. At one point, the computer market’s estimated worth was a bit more than $11 billion, and IBM’s five biggest competitors accounted for about $2 billion, with almost all of the rest going to IBM.

So it was somewhat surprising that IBM didn’t roll out the personal computer first, or at least very early. Even companies that made “small” computers for the day, like Digital Equipment Corporation or Data General, weren’t really expecting the truly personal computer. That push came from companies no one had heard of at the time, like MITS, SWTP, IMSAI, and Commodore. Continue reading “Clone Wars: IBM Edition” →

Ask Hackaday: Do You Curb Shop Components?

January 13, 2026 by 71 Comments

I’m not proud. When many of us were kids, we were unabashedly excited when trash day came around because sometimes you’d find an old radio or — jackpot — an old TV out by the curb. Then, depending on its size, you rescued it, or you had your friends help, or, in extreme cases, you had to ask your dad. In those days, people were frugal, so the chances of what you found being fixable were slim to none. If it was worth fixing, the people would have probably fixed it.

While TVs and radios were the favorites, you might have found other old stuff, but in those days, no one was throwing out a computer (at least not in a neighborhood), and white goods like refrigerators and washing machines had very little electronics. Maybe a mechanical timer or a relay, but that’s about it.

Continue reading “Ask Hackaday: Do You Curb Shop Components?” →

Electronic Nose Sniffs Out Mold

January 12, 2026 by 17 Comments

It turns out, that mold is everywhere. The problem is when it becomes too much, as mold infestations can have serious health effects on both humans and animals. Remediation is extremely expensive, too. So there are plenty of benefits to finding mold early. Now, German researchers are proposing an electronic “nose” that uses UV-activated tin oxide nanowires that change resistance in the presence of certain chemicals, and they say it can detect two common indoor mold species.

The nanowire sensors can detect Staachybotrys chartarum and Chaetominum globosum. The real work, though, is in the math used to determine positive versus negative results.

Continue reading “Electronic Nose Sniffs Out Mold” →

Michelson Interferometer Comes Home Cheap

January 12, 2026 by 20 Comments

We suspect there are three kinds of people in the world. People who have access to a Michelson Interferometer and are glad, those who don’t have one and don’t know what one is, and a very small number of people who want one but don’t have one. But since [Longest Path Search] built one using 3D printing, maybe the third group will dwindle down to nothing.

If you are in the second camp, a Michelson interferometer is a device for measuring very small changes in the length of optical paths (oversimplifying, a distance). It does this by splitting a laser into two parts. One part reflects off a mirror at a fixed distance from the splitter. The other reflects off another, often movable, mirror. The beam splitter also recombines the two beams when they reflect back, producing an interference pattern that varies with differences in the path length between the splitter and the mirror. For example, if the air between the splitter and one mirror changes temperature, the change in the refraction index will cause a minute difference in the beam, which will show up using this instrument.

The device has been used to detect gravitational waves, study the sun and the upper atmosphere, and also helped disprove the theory that light is transmitted through a medium known as luminiferous aether.

Continue reading “Michelson Interferometer Comes Home Cheap” →