Optical scientists have discovered a new way to significantly increase the power of fiber lasers while maintaining beam quality, making them a key defense technology in the future against low-cost drones and other applications such as remote sensing.
Researchers from the University of South Australia (UNISA), the University of Adelaide (UOA) and Yale University have demonstrated the potential use of multimode fibers to increase the power of fiber lasers by a factor of 3 9 without degrading the beam quality, allowing them to focus on targets at long distances.
The breakthrough was published in Nature Communications.
Schematic diagram of stimulated Brillouin scattering (SBS) suppression and output focusing. The spatial wavefront of a narrowband laser beam is shaped by a spatial light modulator and excites many modes in a multimode fiber (mmf). Compared to single-mode fiber and single-mode excitation in the same MMF, the SBS threshold power is greatly increased. Above the threshold, SBS causes the power of the backscattered Stokes light to increase rapidly with the input power, while saturating the power of the transmitted signal light. The input wavefront shaping modulates the relative phase of the fiber patterns so that their interference creates a diffraction-limited spot near the fiber output that can be collimated by the lens.
Dr Linh Nguyen, a researcher at the University of South Australia's Institute for Future Industries and co-first author, said the new approach would allow the industry to continue to squeeze extremely high power out of fiber lasers, making them more useful in the defence industry, remote sensing applications and gravitational wave detection.
"High-power fiber lasers are critical in manufacturing and defense, and this importance will become increasingly apparent as inexpensive unmanned aerial vehicles (UAVs) become more widespread on the modern battlefield," Dr. Nguyen said. A swarm of cheap drones can quickly deplete the missile resource, depleting the launch capabilities of military assets and vehicles from performing more critical combat missions. With extremely low cost per launch and light-speed action, high-power fiber lasers are the only viable defense solution in the long term. This is called asymmetric superiority: more expensive high-tech systems can be defeated by the massive use of cheap methods. ”
In terms of providing asymmetric advantages, this advanced capability has the potential to provide a strong deterrent effect, consistent with the goals of the National Defense Strategic Review and AUKUS Pillar 2.
Dr Ori Henderson-Sapir, a project researcher at the Institute of Photonics and Advanced Sensing at the Australian National University, said: "Australia has a long history of developing innovative fibre technologies. Our research puts Australia as a world leader in the development of the next generation of high-power fiber lasers, not only for defence applications, but also for new scientific discoveries. ”
The researchers have demonstrated the technology in fiber lasers and will present their findings at the Western Photonics Conference in San Francisco in early 2024.