arXiv subjects

Mert Ercan

Publications and source records attributed to Mert Ercan.

4 recordsLinked to original sources

arXiv2026

Reconfigurable generation of high-power structured light via nonlinear beam shaping

High-power structured light has a wide range of applications, from material processing and high-capacity optical communications to programmable electron beams, plasmas, and nuclear states. On-demand generation of structured light and adaptive control of beam profiles are essential for many practical applications, but are difficult to achieve at high power. Here, we demonstrate reconfigurable generation of structured light from a high-power multimode-fiber laser amplifier through full-field control of a low-power seed. An efficient nonlinear beam shaping scheme based on a local linear approximation of the complex nonlinear input--output relation is developed and realized in situ. Diverse structured beams such as Gaussian, Bessel, vector and orbital angular momentum beams are directly generated from the fiber amplifier at powers exceeding 500 W. Our scheme enables real-time programmability of structured light and is readily scalable to even higher power levels. This work provides a general framework for controlling high-dimensional nonlinear systems without accurate knowledge or tractable model.

physics.optics↗

arXiv2025

Upper bounds on focusing light through multimode fibers

Wavefront shaping enables precise control of light propagation through multimode fibers (MMFs), facilitating diffraction-limited focusing for applications such as high-resolution single-fiber imaging and high-power fiber amplifiers. While the theoretical intensity enhancement at the focal point is dictated by the number of input degrees of freedom, practical constraints-such as phase-only modulation and experimental noise-impose significant limitations. Despite its importance, the upper bounds of enhancement under these constraints remain largely unexplored. In this work, we establish a theoretical framework to predict the fundamental limits of intensity enhancement with phase-only modulation in the presence of noise-induced phase errors, and we experimentally demonstrate wavefront shaping that approaches these limits. Our experimental results confirm an enhancement factor of 5000 in a large-core MMF, approaching the theoretical upper bound, enabled by noise-tolerant wavefront shaping. These findings provide key insights into the limits of phase-only control in MMFs, with profound implications for single-fiber imaging, optical communication, high-power broad-area fiber amplification, and beyond.

physics.optics↗

arXiv2025

Wavefront shaping enables high-power multimode fiber amplifier with output control

Over the past two decades there have been tremendous advances in high-power fiber lasers, which have provided a powerful tool for science, engineering and defense. A major roadblock for further power scaling of single-frequency fiber laser amplifiers is stimulated Brillouin scattering. Intense efforts were devoted to mitigate this nonlinear process, but mostly limited to single-mode or few-mode fiber amplifiers which have good beam quality. Here we explore a highly multimode fiber amplifier, where stimulated Brillouin scattering is greatly suppressed due to reduction of light intensity in a large fiber core and broadening of Brillouin scattering spectrum by multimode excitation. To control the output beam profile, we apply spatial wavefront shaping technique to the input light of a nonlinear amplifier to focus the output beam to a diffraction-limited spot outside the fiber facet. Our multimode fiber amplifier can operate at high power with high efficiency and narrow linewidth which ensures high coherence. Optical wavefront shaping enables coherent control of multimode laser amplification, with potential applications in coherent beam combining, large-scale interferometry and directed energy delivery.

physics.optics↗

arXiv2024

Output beam shaping of a multimode fiber amplifier

Multimode fibers provide a promising platform for realizing high-power laser amplifiers with suppressed nonlinearities and instabilities. The potential degradation of optical beam quality has been a major concern for highly multimode fiber amplifiers. We show numerically that the beam propagation factor M2 of a single-frequency multimode fiber amplifier can be reduced to nearly unity by shaping the input or output beam profile with spatial phase-masks. Our method works for narrowband multimode fiber amplifiers with strong gain saturation, pump depletion, random mode coupling and polarization mixing. The numerical results validate our approach of utilizing highly multimode excitation to mitigate nonlinear effects in high-power fiber amplifiers and performing input wavefront shaping to control output beam profile and polarization state.

physics.optics↗