Plasmonic Modulators Directly Convert Terahertz Waves To Optical Signals

April 14, 2025 by Maya Posch 5 Comments

A major bottleneck with high-frequency wireless communications is the conversion from radio frequencies to optical signals and vice versa. This is performed by an electro-optic modulator (EOM), which generally are limited to GHz-level signals. To reach THz speeds, a new approach was needed, which researchers at ETH Zurich in Switzerland claim to have found in the form of a plasmonic phase modulator.

Although sounding like something from a Star Trek episode, plasmonics is a very real field, which involves the interaction between optical frequencies along metal-dielectric interfaces. The original 2015 paper by [Yannick Salamin] et al. as published in Nano Letters provides the foundations of the achievement, with the recent paper in Optica by [Yannik Horst] et al. covering the THz plasmonic EOM demonstration.

The demonstrated prototype can achieve 1.14 THz, though signal degradation begins to occur around 1 THz. This is achieved by using plasmons (quanta of electron oscillators) generated on the gold surface, who affect the optical beam as it passes small slots in the gold surface that contain a nonlinear organic electro optic material that ‘writes’ the original wireless signal onto the optical beam.

Creating A Somatosensory Pathway From Human Stem Cells

April 11, 2025 by Maya Posch No comments

Human biology is very much like that of other mammals, and yet so very different in areas where it matters. One of these being human neurology, with aspects like the human brain and the somatosensory pathways (i.e. touch etc.) being not only hard to study in non-human animal analogs, but also (genetically) different enough that a human test subject is required. Over the past years the use of human organoids have come into use, which are (parts of) organs grown from human pluripotent stem cells and thus allow for ethical human experimentation.

For studying aspects like the somatosensory pathways, multiple of such organoids must be combined, with recently [Ji-il Kim] et al. as published in Nature demonstrating the creation of a so-called assembloid. This four-part assembloid contains somatosensory, spinal, thalamic and cortical organoids, covering the entirety of such a pathway from e.g. one’s skin to the brain’s cortex where the sensory information is received.

Such assembloids are – much like organoids – extremely useful for not only studying biological and biochemical processes, but also to research diseases and disorders, including tactile deficits as previously studied in mouse models by e.g. [Lauren L. Orefice] et al. caused by certain genetic mutations in Mecp2 and other genes, as well as genes like SCN9A that can cause clinical absence of pain perception.

Using these assembloids the development of these pathways can be studied in great detail and therapies developed and tested.

You Shouldn’t Build An X-Ray Machine, But You Could

April 9, 2025 by Al Williams 18 Comments

Ever wanted your own X-ray machine? Of course you have! Many of us were indoctrinated with enticing ads for X-ray specs and if you like to see what’s inside things, what’s better than a machine that looks inside things? [Hyperspace Pirate] agrees, and he shows you the dangers of having your own X-ray machine in the video below.

The project starts with an X-ray tube and a high voltage supply. The tube takes around 70,000 volts which means you need a pretty stout supply, an interesting 3D printed resistor, and some mineral oil.

The output display? A normal camera. You also need an intensifying screen, which is just a screen with phosphor or something similar. He eventually puts everything in lead and reminds you that this is a very dangerous project and you should probably skip it unless you are certain you know how to deal with X-ray dangers.

Overall, looks like a fun project. But if you want real credit, do like [Harry Simmons] and blow your own X-ray tube, too. We see people build similar machines from time to time. You shouldn’t, but if you do, remember to be careful and to tell us about it!

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A Tale Of Nuclear Shenanigans From Down Under

April 6, 2025 by Jenny List 47 Comments

It’s likely that among the readers of this article there will be many who collect something. Whether it’s rare early LEDs or first-year-of-manufacture microprocessors, you’ll scour the internet to find them, and eagerly await mystery packages from the other side of the world.

There’s a tale emerging from Australia featuring just such a collector, whose collection now has him facing a jail sentence for importing plutonium. The story however is not so clear-cut, featuring a media frenzy and over-reaction from the authorities worthy of Gatwick Airport. [Explosions&Fire] has a rather long video unpacking the events, which we’ve placed below the break.

Emmanuel Lidden is an element collector, someone who tries to assemble an entire Periodic Table in their collection. He ordered a range of elements from an American element collectors’ supply website, including samples of plutonium and thorium. He seems to have been unaware he was committing any crime, with the microscopic samples available from legitimate websites with no warnings attached. The case becomes murkier as the Australian authorities flagged the thorium sample and instructed the courier not to deliver it, which they did anyway. Then a raid of the type you’d expect for the terrorists who stole the plutonium in Back To The Future was launched, along with that Gatwick-esque media frenzy.

We’re inclined to agree that the penalty likely to be meted out to him for buying a sliver of a Soviet smoke detector embedded in a Lucite cube seems overly steep, but at the same time his obvious naivety over dealing in radioactive materials marks him as perhaps more than a little foolhardy. It’s something over which to ponder though, have we managed to amass anything illegal disguised as outdated devices? Have you? Perhaps it’s something to discuss in the comments.

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Dwingeloo telescope with sun shining through

Dwingeloo To Venus: Report Of A Successful Bounce

March 28, 2025 by Heidi Ulrich 14 Comments

Radio waves travel fast, and they can bounce, too. If you are able to operate a 25-meter dish, a transmitter, a solid software-defined radio, and an atomic clock, the answer is: yes, they can go all the way to Venus and back. On March 22, 2025, the Dwingeloo telescope in the Netherlands successfully pulled off an Earth-Venus-Earth (EVE) bounce, making them the second group of amateurs ever to do so. The full breakdown of this feat is available in their write-up here.

Bouncing signals off planets isn’t new. NASA has been at it since the 1960s – but amateur radio astronomers have far fewer toys to play with. Before Dwingeloo’s success, AMSAT-DL achieved the only known amateur EVE bounce back in 2009. This time, the Dwingeloo team transmitted a 278-second tone at 1299.5 MHz, with the round trip to Venus taking about 280 seconds. Stockert’s radio telescope in Germany also picked up the returning echo, stronger than Dwingeloo’s own, due to its more sensitive receiving setup.

Post-processing wasn’t easy either. Doppler shift corrections had to be applied, and the received signal was split into 1 Hz frequency bins. The resulting detections clocked in at 5.4 sigma for Dwingeloo alone, 8.5 sigma for Stockert’s recording, and 9.2 sigma when combining both datasets. A clear signal, loud and proud, straight from Venus’ surface.

The experiment was cut short when Dwingeloo’s transmitter started failing after four successful bounces. More complex signal modulations will have to wait for the next Venus conjunction in October 2026. Until then, you can read our previously published article on achievements of the Dwingeloo telescope.

General Fusion Claims Success With Magnetized Target Fusion

March 27, 2025 by Maya Posch 21 Comments

It’s rarely appreciated just how much more complicated nuclear fusion is than nuclear fission. Whereas the latter involves a process that happens all around us without any human involvement, and where the main challenge is to keep the nuclear chain reaction within safe bounds, nuclear fusion means making atoms do something that goes against their very nature, outside of a star’s interior.

Fusing helium isotopes can be done on Earth fairly readily these days, but doing it in a way that’s repeatable — bombs don’t count — and in a way that makes economical sense is trickier. As covered previously, plasma stability is a problem with the popular approach of tokamak-based magnetic confinement fusion (MCF). Although this core problem has now been largely addressed, and stellarators are mostly unbothered by this particular problem, a Canadian start-up figures that they can do even better, in the form of a nuclear fusion reactors based around the principle of magnetized target fusion (MTF).

Although General Fusion’s piston-based fusion reactor has people mostly very confused, MTF is based on real physics and with GF’s current LM26 prototype having recently achieved first plasma, this seems like an excellent time to ask the question of what MTF is, and whether it can truly compete billion-dollar tokamak-based projects.

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Building The Simplest Atomic Force Microscope

March 23, 2025 by Elliot Williams 23 Comments

Doing it yourself may not get you the most precise lab equipment in the world, but it gets you a hands-on appreciation of the techniques that just can’t be beat. Today’s example of this adage: [Stoppi] built an atomic force microscope out of mostly junk parts and got pretty good results, considering. (Original is in German; read it translated here.)

The traditional AFM setup uses a piezo micromotor to raise and lower the sample into a very, very fine point. When this point deflects, it reads the height from the piezo setup and a motor stage moves on to the next point. Resolution is essentially limited by how fine a point you can make and how precisely you can read from the motion stages. Here, [stoppi]’s motion stage follows the traditional hacker avenue of twin DVD sleds, but instead of a piezo motor, he bounces a laser off of a mirror on top of the point and reads the deflection with a line sensor. It’s a clever and much simpler solution.

A lot of the learnings here are in the machine build. Custom nichrome and tungsten tips are abandoned in favor of a presumably steel compass tip. The first-draft spring ended up wobbling in the X and Y directions, rather than just moving in the desired Z, so that mechanism got reinforced with aluminum blocks. And finally, the line sensors were easily swamped by the laser’s brightness, so neutral density filters were added to the project.

The result? A nice side effect of the laser-bouncing-off-of-mirror setup is that the minimum resolvable height can be increased simply by moving the line sensors further and further away from the sample, multiplying the deflection by the baseline. Across his kitchen, [stoppi] is easily able to resolve the 35-um height of a PCB’s copper pour. Not bad for junk bin parts, a point from a crafts store, and a line sensor.

If you want to know how far you can push a home ~~AFM~~ microscope project, check out [Dan Berard]’s absolutely classic hack. And once you have microscope images of every individual atom in the house, you’ll, of course, want to print them out.