Stack of Si3N4-LiNbO3 forming the integrated laser and integrated into test setup (d). (Credit: Snigirev et al., 2023)

Fast Adjustable Lasers Using Lithium Niobate Integrated Photonics

August 4, 2023 by Maya Posch 14 Comments

Making lasers smaller and more capable of rapidly alternating between frequencies, while remaining within a narrow band, is an essential part of bringing down the cost of technologies such as LiDAR and optical communication. Much of the challenge here lies understandably in finding the right materials that enable a laser which incorporates all of these properties.

A heterogeneous Si3N4–LiNbO3 chip as used in the study. (Credit: Snigirev et al., 2023)

Here a recent study by [Viacheslav Snigirev] and colleagues (press release) demonstrates how combining the properties of lithium niobate (LiNbO₃) with those of silicon nitride (Si₃N₄) into a hybrid (Si₃N₄)–LiNbO₃ wafer stack allows for an InP-based laser source to be modulated in the etched photonic circuitry to achieve the desired output properties.

Much of the modulation stability is achieved through laser self-injection locking via the microresonator structures on the hybrid chip. These provide optical back reflection that forces the laser diode to resonate at a specific frequency, providing the frequency lock. What enables the fast frequency tuning is that this is determined by the applied voltage on the microresonator structure via the formed electrodes.

With a LiDAR demonstration in the paper that uses one of these hybrid circuits it is demonstrated that the direct wafer bonding approach works well, and a number of optimization suggestions are provided. As with all of these studies, they build upon years of previous research as problems are found and solutions suggested and tested. It would seem that thin-film LiNbO₃ structures are now finding some very useful applications in photonics.

(Heading image: Stack of Si₃N₄-LiNbO₃ forming the integrated laser and integrated into test setup (d). (Credit: Snigirev et al., 2023) )

Accelerating Electrons To TeV Levels Using Curved Laser Beams

August 1, 2023 by Maya Posch 12 Comments

There are many applications for particle accelerators, even outside research facilities, but for the longest time they have been large, cumbersome machines, not to mention very expensive to operate. Here laser wakefield accelerators (LWFAs) are a promising alternative, which uses lasers to create accelerated particles along the wake in a plasma field. One of the major struggles has been with reinjecting the thus accelerated particles into another stage of a multi-stage accelerator, which would be required to obtain energies closer to one TeV. In this area researchers have now demonstrated a way around this, by using curved channels for the laser beams (paywalled paper) which inject the laser beam into the continuous cavity. Continue reading “Accelerating Electrons To TeV Levels Using Curved Laser Beams” →

DIY Laser For Ablating Metal

July 17, 2023 by Bryan Cockfield 51 Comments

For those who wish to go beyond through-hole construction on perfboard for their circuit boards, a printed circuit board is usually the next step up. Allowing for things like surface-mount components, multi-layer boards, and a wider array of parts, they are much more versatile but do have a slight downside in that they are a little bit harder to make. There are lots of methods for producing them at home or makerspace, though, and although we’ve seen plenty of methods for their production like toner transfer, photoresist, and CNC milling, it’s also possible to make them using laser ablation, although you do need a special laser to get this job done.

The problem with cutting copper is that it reflects infra-red, so a higher-wavelength ~~blue~~ green laser is used instead. And because you want to ablate the copper, but not melt the surrounding areas or cut straight through the board, extremely short, high-power pulses are the way to go. Here, the [Munich Fab Lab] is using 9 kW pulses of around 30 microseconds each. With these specifications the copper is ablated from the surface of the board allowing for fine details in the range of about 20 µm, which is fine enough for just about any circuit board. The design of the laser head itself is worth a look.

Aside from the laser, the rest is standard CNC machine fodder, but with an emphasis on safety that’s appropriate for a tool in a shared workspace, and the whole project is published under an open license and offers an affordable solution for larger-scale PCB production with extremely fine resolution and without the need for any amounts of chemicals for the more common PCB production methods. There is a lot more information available on the project’s webpage and its GitHub page as well.

Of course, there are other methods of producing PCBs by laser if you happen to have a 20 W fiber laser just kicking around.

No Moving Parts LiDAR

July 6, 2023 by Al Williams 29 Comments

Self-driving cars often use LiDAR — think of it as radar using light beams. One limitation of existing systems is they need some method of scanning the light source around, and that means moving parts. Researchers at the University of Washington have created a laser on a chip that uses acoustic waves to bend the laser, avoiding physically moving parts. The paper is behind a paywall, but the University has a summary poster, and you can also find an overview over on [Geekwire].

The resulting IC uses surface acoustic waves and can image objects more than 100 feet away. We would imagine this could be helpful for other applications like 3D scanning, too. The system weighs less than a conventional setup, too, so that would be valuable in drones and similar applications.

Continue reading “No Moving Parts LiDAR” →

Growing Simple Crystals For Non-Linear Optics Experiments

July 6, 2023 by Dan Maloney 18 Comments

Here’s an exercise for you: type “crystals” into your favorite search engine and see what you get. If you’re anything like us, you’ll get a bunch of pseudoscientific posts about the healing power of crystals, along with offers to buy the same at exorbitant prices. But woo-woo aside, certain crystals do have seemingly magical powers — like the ability to turn light from one color into another.

None of this is magic, of course. Rather, as optics aficionado [Les Wright] explains, non-linear optics is all about physics. Big physics, too, like the kind that made the National Ignition Facility the first fusion research outfit to reach the “break-even” point, at least in terms of optical energy. To do so, they need to convert megajoules of infrared laser beams all the way across the visible spectrum into the ultraviolet, relying on huge crystals of deuterated potassium dihydrogen phosphate (KDP) to do so. Depending on how they’re cut, crystals of these sorts have non-linear optical properties like second-harmonic generation, which combines two input photons into a single output photon with twice the energy of the original. This results in a halving of the wavelength of the input, which doubles the frequency.

While the process used at the NIF produces crystals of enormous proportions, [Les] has more modest needs and thus a simpler process. His KDP is an off-the-shelf chemical, nothing fancy about it, which is added to boiling water to make a saturated solution. A little of the solution is poured out into a watch glass to make seed crystals, and everything is allowed to cool slowly. A nice seed crystal is glued to a piece of monofilament fishing line and suspended in the saturated solution, and with enough time a good-sized crystal forms. Placed into the beam path of a 1,064 nm IR laser and rotated carefully relative to the beam, the crystal easily produces a brilliant green laser output.

This is fascinating stuff, and we’re looking forward to seeing where [Les] goes with this. Polishing the crystals to make them optically cleaner would be a good next step, as would perhaps growing even larger crystals.

Continue reading “Growing Simple Crystals For Non-Linear Optics Experiments” →

Laser Projector Built From An Old Hard Drive

May 12, 2023 by Bryan Cockfield 41 Comments

Spinning hard drives are being phased out of most consumer-grade computers in favor of faster technology like solid-state drives and their various interfaces. But there’s still millions of them in circulation that will eventually get pulled from service — so what do we do with them? If you’ve got one that would otherwise be going in the garbage, they can be turned into some other interesting devices like this laser text projector.

Even the slowest drives spin at around 5000 RPM, which is perfect for this type of application. The device works by mounting twelve mirrors, each at a slightly different angle, on a drum which is spun by the drive’s motor. Bouncing a laser off of the spinning drum results in a projection of twelve horizontal lines. By rapidly switching the laser on and off depending on which mirror it’s pointing at, the length of each line can be controlled.

Thanks to persistence of vision, that allows you to show text on the surface that the laser is projected on. At speeds this high, it took [Ben] of Ben Makes Everything quite a few iterations to get it to a usable space. From sensors that were too slow to lasers not bright enough to 3D prints that were not accurate enough, he goes through the design of his build and the process in excellent detail.

After solving all of the problems including building his own constant-current laser power supply, and burning up a few laser diodes in the process, [Ben] has a laser projector capable of displaying readable text at a great distance which is also portable, running on a 12 V power supply. There are some possible areas of improvement that he notes as well, such as an unbalanced 3D printed part causing a bit of a wobble and the Arduino controller not being fast enough for more text. But it’s an impressive project nonetheless, similar to a two-mirror version we saw some time ago but with the ability to display text as well.

Continue reading “Laser Projector Built From An Old Hard Drive” →

Hackaday Links: May 7, 2023

May 7, 2023 by Dan Maloney 39 Comments

More fallout for SpaceX this week after their Starship launch attempt, but of the legal kind rather than concrete and rebar. A handful of environmental groups filed the suit, alleging that the launch generated “intense heat, noise, and light that adversely affects surrounding habitat areas and communities, which included designated critical habitat for federally protected species as well as National Wildlife Refuge and State Park lands,” in addition to “scatter[ing] debris and ash over a large area.”

Specifics of this energetic launch aside, we always wondered about the choice of Boca Chica for a launch facility. Yes, it has all the obvious advantages, like a large body of water directly to the east and being at a relatively low latitude. But the whole area is a wildlife sanctuary, and from what we understand there are still people living pretty close to the launch facility. Then again, you could pretty much say the same thing about the Cape Canaveral and Cape Kennedy complex, which probably couldn’t be built today. Amazing how a Space Race will grease the wheels of progress.

Continue reading “Hackaday Links: May 7, 2023” →