Light propagation in high-power multicore fibers

• Applicant: Dr.-Ing. Cesar Jauregui Misas, Ph.D.
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 524265936

Fiber laser systems have gained a solid reputation as average-power scalable laser architectures. However, the performance scaling of high-power fiber laser systems is hindered by several phenomena related to either the non-linear behavior of the refractive index of the fiber or to thermal effects. One solution is to exploit the concept of parallelization. Hereby the signal to be amplified is split in N sub-beams, that will be simultaneously amplified in as many parallel amplification channels. The main problem of the classic implementation of the concept described above (i.e. using separated amplifiers) is that the system complexity, cost and footprint, scale linearly with the number of amplification channels. This makes the scaling of these systems to channel counts larger than a few tens of emitters impractical. In order to break this linear dependency and, therefore, to allow for larger channel counts, it is possible to integrate all the amplification channels inside of a single fiber. This constitutes the so-called multicore fiber concept. Multicore fibers are not simply a mere integration of amplification channels in a device, though. They constitute highly sophisticated waveguides in which complex interactions of the electromagnetic radiation can take place. On top of that, the integration of a large channel count (e.g. 100 to 1000) leads naturally to multicore fibers with dimensions that are several orders of magnitude larger than the wavelength of the light involved in the laser process. The transmission of light in such large structures is beyond what is currently known about electromagnetic propagation in waveguides. In fact, it is expected that the light will travel in a regime that is between guidance and free-space propagation, something that has not been studied before. This project aims at investigating the propagation and electromagnetic interaction of light in large multicore fibers. In particular, this includes studying the propagation of pump light along the cladding, the propagation of polarized light in the fiber cores and the complex intra- and inter-core modal interactions including the effect of transverse mode instability in multicore fibers. In fact, this application is conceived to help reaching the goals set in the Heisenberg project and it is, therefore, intimately intertwined with the activities of that project.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Jens Limpert