Will Photonic-Crystal Lasers Revolutionize 3D Printing?

Powder bed fusion (PBF) for metals and polymers predominantly utilizes lasers as the primary heat source. Some directed energy deposition (DED) technologies also employ lasers, while various vat polymerization methods depend on them as well. Traditionally, lasers have either been considered weak or energy-intensive and costly, or sometimes both. Lasers are a major cost component in all laser-based 3D printing technologies.

Now, a team from Kyoto University, in collaboration with researchers from National Yang Ming Chiao Tung University, the University of Texas at Arlington, and the University of Glasgow, have highlighted significant advancements in Photonic-Crystal Surface-Emitting Lasers (PCSELs). These improvements could make PCSELs increasingly relevant for 3D printing applications. PCSEL systems are cost-effective, can be assembled in arrays, and offer the ability to be steered. They could provide high output power and excellent beam quality, and are manufactured similarly to other electronics. Since their invention in 1999 and subsequent commercialization by Vector Photonics, these lasers have shown great potential for applications not only in LiDAR but also in manufacturing.

Lasers in 3D Printing

CO2 lasers, along with others such as argon lasers, are extensively used in a variety of applications, including 3D printing. For instance, EOS’ Formiga systems incorporate a 30W CO2 laser. YAG and other solid-state lasers are commonly used in vat polymerization. A specific type of solid-state laser, known as a fiber laser, is also prevalently used; for example, SLM Solutions employs IPG fiber lasers. Semiconductor lasers, also referred to as diode lasers, are utilized in low-cost PBF systems and in numerous laser cutters and similar devices.

There are indeed several additional categories of lasers and many other types as well. Vertical-cavity surface emitting lasers (VCSELs) are emerging and could be utilized for part heating, while Seurat hopes to use optically addressable light valve (OALV) components to print an entire area in one go. Green lasers from Trumpf have enabled copper 3D printing in powder bed fusion, while EOS employs a 1 KW fiber laser for the same material. Prima Additive, on the other hand, uses blue lasers for DED. Often, different types of lasers are used by competing machines. Depending on various factors, a specific laser might be more suitable for a particular material or machine.

The Potential of PCSELs

PCSEL arrays can operate coherently, allowing their combined power to be focused into a tiny spot, which could enhance capabilities in laser cutting and 3D printing. They can also function at different wavelengths, which may be optimized for specific processes or materials. By allowing the array to perform the steering, these lasers could potentially illuminate different points simultaneously, move more quickly, eliminate the need for an additional motion stage, dispense with galvanometers and other components, and reduce the size and complexity of the laser equipment needed for high-power jobs.

What is certain is that photonic crystals could fundamentally change the efficiency of laser production. These crystals are structured with specific patterns that focus the beam powerfully out of the top of the unit, rather than dispersing it outward. It’s kind of as if you have a tap spewing water in any which way, put a garden hose nozzle on it and the water can become focused and more powerful.  Or it is as if you have a shower head with different settings that you can select with a twist. Through pushing different apertures in place you can change the same shower and water volume into a tight focused powerful singular jet of water, a gentle rain like sprinkle or a few high intensity beams.

The researchers describe the technology like this:

¨The operating principle is this: When waves of that length are generated in the active layer, the holes in the neighboring photonic-crystal layer act like tiny mirrors, bending the light both backward and sideways. The combined effect of multiple such diffractions creates a 2D standing wave, which is then amplified by the active layer. Some of this oscillating light also diffracts upward and downward and leaks out the laser’s top, producing a surface beam of a single wavelength.”

The team then implemented a novel approach by creating a double lattice layer: one layer with circular holes and another with elliptical holes. This design effectively eliminates interference, allowing the beam to become even brighter. This innovation enabled them to produce a 10-watt beam. With further optimization, specifically by channeling reflections, they were able to enhance the output power even more.

In 2023, with a “3-mm emission diameter, it could lase continuously at up to 50 W while sustaining a beam that diverged a minuscule one-twentieth of a degree. We even used it to cut through steel. As the bright, beautiful beam carved a disc out of a metal plate 100 μm thick, our entire lab huddled around, watching in amazement.¨

Taking on the Laser Market with PCSELs

Lasers not only compete with various technologies within their domain but also with different technologies across sectors. Industrial cutting tools, for instance, drive substantial demand for high-powered lasers. Meanwhile, inexpensive desktop lasers and a range of consumer-level devices have significantly reduced the cost of certain laser categories. Lasers are utilized in a broad array of industrial and electronics applications. From the barcode scanner in your local supermarket to the LIDAR systems in assisted-driving vehicles, and even the light shows at your local disco, lasers are ubiquitous. In the realm of 3D printing, lasers enhance the performance of various technologies and, specifically, diode lasers are having disruptive effects on pricing and the entry of new market players. CO2 lasers may consume more power than fiber lasers, and depending on the wattage or specific application, one type could be cheaper or more suitable than another.

One of the most promising developments lies in semiconductor-based lasers, largely because they have the potential to become significantly cheaper or more powerful, especially when configured in arrays. This potential is bolstered by the ongoing advancements in the semiconductor industry, which itself depends heavily on laser technology, and by the relative ease and lower cost of manufacturing these lasers. In 3D printing, the ability to precisely and quickly heat specific elements is crucial, and ideally, we would like to illuminate an entire layer or even an entire part at once. Arrays of lasers, such as those in EOS’s LaserProFusion approach, could fundamentally transform the industry.

The research team aims to further expand their array to achieve even more powerful results, with aspirations to develop 1,000-watt, 1-centimeter PCSEL designs, and eventually, 3-centimeter lasers capable of delivering output powers of 10 kilowatts. If they can achieve this level of power, significantly smaller and less power-hungry laser units could indeed revolutionize 3D printing, among many other applications. However, it remains uncertain how long it will take for this 25-year-old technology to reach these milestones.