A Russian pro-Kremlin media channel released new footage this week showing what it claims is the combat use of a laser weapon against Ukrainian drones in Russia’s Belgorod region, near the border with Ukraine, marking another public appearance of a Chinese-made directed-energy system in Russian service. The video, published on January 2026, shows a stationary […]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.
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.
Random lasers also depend on gain, but they have no mirrors. Instead, the gain medium is within or contains some material that highly scatters photons. For example, rough crystals or nanoparticles may act as scattering media to form random lasers.
The scattering has photons bounce around at random. Some of the photons will follow long paths, and if the gain exceeds the losses along those paths, laser emission occurs. Incoherent random lasers that use powder (to scatter) or a dye (as gain medium) tend to have broadband output. However, coherent random lasers produce sharp spectral lines much like a conventional laser. They are, though, more difficult to design and control.
Random lasers are relatively new, but they are very simple to construct. Since the whole thing depends on randomness, defects are rarely fatal. The downside is that it is difficult to predict exactly what they will emit.
There are some practical use cases, including speckle-free illumination or creating light sources with specific fingerprints for identification.
Biological tissue often can provide scattering for random lasers. Researchers have used peacock feathers, for example. Attempts to make cells emit laser light are often motivated by their use as cellular tags or to monitor changes in the laser light to infer changes in the cell itself.
The video below isn’t clearly using a random laser, but it gives a good overview of why researchers want your cells to emit laser light.
You may be thinking: “Isn’t this just amplified spontaneous emission?” While random lasers can resemble amplified spontaneous emission (ASE), true random lasing exhibits a distinct turn-on threshold and, in some cases, well-defined spectral modes. ASE will exhibit a smooth increase in output as the pump energy increases. A random laser will look like ASE until you reach a threshold pump energy. Then a sharp rise will occur as the laser modes suddenly dominate.
We glossed over a lot about conventional lasers, population inversion, and related topics. If you want to know more, we can help.
President of Azerbaijan Ilham Aliyev opened the reconstructed Tartar Electromechanical Plant on January 13, during a visit in which newly developed directed-energy counter-drone systems were shown for the first time. The plant has been modernized as part of Azerbaijan’s expanding defense-industrial program overseen by the Ministry of Defense Industry. According to information provided during the […]You can hear sound, of course, but what if you could see it with a laser? That’s what [Goosetopherson] thought about, and thus a new project that you can see in the video below was born.
The heart of the project is an I2S chip and an ESP32. Sound energy deforms a plastic film that causes a mirror to move. The moving mirror alters the course of the laser’s beam.
An important part of the project is the 3D printed enclosure designed in Fusion. Some wires are routed through during printing, and there are heat-set inserts.
If you haven’t run into it before, you can think of I2S as I2C for stereo audio. It uses a synchronous protocol to push audio data using three wires. The board in question takes the digital data and decodes it to drive the speaker.
This is a simple project that would lend itself to lots of substitutions if you decide to replicate it. In fact, we’ve seen a version of this that is nothing more than a Bluetooth speaker, some plastic film, a mirror, and a laser.
An accessible 3D printer for metals has been the holy grail of amateur printer builders since at least the beginning of the RepRap project, but as tends to be the case with holy grails, it’s proven stubbornly elusive. If you have the resources to build it, though, it’s possible to replicate the professional approach with a selective laser melting (SLM) printer, such as the one [Travis Mitchell] built (this is a playlist of nine videos, but if you want to see the final results, the last video is embedded below).
Most of the playlist shows the process of physically constructing the machine, with only the last two videos getting into testing. The heart of the printer is a 500 Watt fiber laser and a galvo scan head, which account for most of the cost of the final machine. The print chamber has to be purged of oxygen with shielding gas, so [Travis] minimized the volume to reduce the amount of argon needed. The scan head therefore isn’t located in the chamber, but shines down into it through a window in the chamber’s roof. A set of repurposed industrial servo motors raises and lowers the two pistons which form the build plate and powder dispenser, and another servo drives the recoater blade which smooths on another layer of metal powder after each layer.
As with any 3D printer, getting good first-layer adhesion proved troublesome, since too much power caused the powder to melt and clump together, and too little could result in incomplete fusion. Making sure the laser was in focus improved things significantly, though heat management and consequent warping remained a challenge. The recoater blade was originally made out of printed plastic, with a silicone cord along the edge. Scraping along hot fused metal in the early tests damaged it, so [Travis] replaced it with a stainless steel blade, which gave much more consistent performance. The final results looked extremely promising, though [Travis] notes that there is still room for redesign and improvement.
This printer joins the very few other DIY SLM machines we’ve seen, though there is an amazingly broad range of other creative ideas for homemade metal printers, from electrochemical printers to those that use precise powder placement.
Israel’s Ministry of Defense and Rafael Advanced Defense Systems have delivered the first operational Iron Beam high-power laser air defense system to the Israel Defense Forces, the ministry said Sunday, marking the system’s formal entry into active service. According to a statement from the Israel Ministry of Defense, the handover took place during an official […]
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