Stable lasers developed with mixed materials focus on autonomous vehicle, etc

Researchers printed microscale lenses directly onto optical fibers, allowing them to tightly combine the fibers and laser crystals into a single laser oscillator.

Scientists have used 3D printing polymers in new micro optical technology, which can reduce the size of lasers and be used in various new applications, including the laser radar system for autonomous vehicle technology and cancer treatment.

A group of researchers from the University of Stuttgart in Germany demonstrated 3D printed polymer based micro optical devices that can withstand the heat and power levels generated inside the laser. Specifically, they use 3D printers to directly manufacture microscale optical devices on fibers, displaying a compact combination of fibers and laser crystals within a single laser oscillator.

"The first implementation of this 3D printed optical device in real-world lasers demonstrates the tolerance of optical devices to damage and the stability of small-sized laser applications," said Simon Angstenberger, research leader at the University's Fourth Institute of Physics.

"By using 3D printing to manufacture high-quality micro optical devices directly on the glass fibers used inside the laser, we have greatly reduced the size of the laser," he explained.

So far, 3D printed optical devices have been mainly used for low-power applications such as endoscopy, but this study has also paved the way for their use in high-power applications. Angstenberger said that this may be useful in lithography and laser marking applications, such as in medical applications.

"We demonstrate that these 3D micro optical devices printed on optical fibers can be used to focus a large amount of light on a single point, which may be useful for medical applications such as precise destruction of cancer tissue," he said.

Stuttgart researchers used a 3D printing method called two-photon polymerization in their work. This technology focuses infrared laser into UV sensitive photoresist, where the focus area of the laser will simultaneously absorb two infrared photons. Researchers say this helps harden UV corrosion inhibitors.

In addition, researchers say that moving the focus can create various shapes with high precision, making this method very suitable for creating miniaturized optical devices and allowing for new functionalities, such as creating free-form optical components or complex lens systems.

In their recent work, researchers used Nanoscribe's 3D printer to manufacture lenses with a diameter of 0.25 millimeters and a height of 80 micrometers at the end of fibers of the same diameter. This technology requires several precise steps that require precision. Researchers use commercial software to design optical components and then place the fibers into a 3D printer. Then, they printed a small structure at the end of the fiber.

They said that after the printing was completed, the team began assembling the laser and laser cavity, using fibers to form a part of the cavity, thereby forming a hybrid fiber crystal laser instead of crystals typically made from expensive and bulky mirrors.

The lens printed at the end of the optical fiber focuses and collects or couples light entering and exiting the laser crystal. The researchers also glued the optical fibers onto the bracket to make the laser system more stable and less susceptible to the influence of air turbulence. Researchers say that, in summary, the sum of crystals and printed lenses is only 5 X 5 square centimeters.

Angstenberger acknowledges that even after implementing these detailed steps in their research, the team is unsure whether the resulting optical structure can function properly under significant heat and optical power generated within the laser cavity.

However, researchers found after recording laser power for several hours that "they are surprisingly stable, and even after running the laser for several hours, we cannot observe any damage on the lens," he said.

In addition, the team captured scanning electron microscopy images of the optical components after using them in the laser cavity, and these images did not show any visible damage. "Interestingly, we found that printed optical devices are more stable than the commercial fiber Bragg gratings we use, which ultimately limits our maximum power," Angstenberger added.

The researchers published a paper on their work in the journal Optics Letters. They said their next step will be to optimize the efficiency of printed optical devices.

The team envisions that larger optical fibers with optimized free surface and aspherical lens designs, or lens combinations printed directly on the fibers, can help improve output power. Researchers also hope to display different crystals in lasers, which can allow for customized output for specific applications.

Source: Laser Net