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Power-Scalable Generation of High-Order Optical Vortices Via Coherent Beam Combining

Hossein Fathi, Rafael F. Barros, Regina Gumenyuk

Abstract

Structured light beams, such as optical vortices carrying orbital angular momentum, are essential for applications ranging from low-power optical communications to high-intensity laser-matter interactions. However, scaling their power and energy while preserving complex phase and spatial structures remains a fundamental challenge. In this work, we demonstrate coherent beam combining as a versatile and scalable method for generating high-power structured beams without limitations on topological charge or spatial structure, while maintaining exceptionally high modal purity. We experimentally implement coherent beam combining for optical vortex beams with topological charges l = 1, 5, and 8, achieving a combined average power of 100 W and a peak power of 100 kW, with combining efficiencies of 95.0%, 93.9%, and 91.2%, respectively. Off-axis digital holography confirms that the phase and intensity profiles of the combined beams retain high modal purity, even at high topological charges. These results establish coherent beam combining as an effective route to high modal purity structured light at high power levels, unlocking new opportunities for advanced photonics and high-intensity light-matter interaction studies.

Power-Scalable Generation of High-Order Optical Vortices Via Coherent Beam Combining

Abstract

Structured light beams, such as optical vortices carrying orbital angular momentum, are essential for applications ranging from low-power optical communications to high-intensity laser-matter interactions. However, scaling their power and energy while preserving complex phase and spatial structures remains a fundamental challenge. In this work, we demonstrate coherent beam combining as a versatile and scalable method for generating high-power structured beams without limitations on topological charge or spatial structure, while maintaining exceptionally high modal purity. We experimentally implement coherent beam combining for optical vortex beams with topological charges l = 1, 5, and 8, achieving a combined average power of 100 W and a peak power of 100 kW, with combining efficiencies of 95.0%, 93.9%, and 91.2%, respectively. Off-axis digital holography confirms that the phase and intensity profiles of the combined beams retain high modal purity, even at high topological charges. These results establish coherent beam combining as an effective route to high modal purity structured light at high power levels, unlocking new opportunities for advanced photonics and high-intensity light-matter interaction studies.
Paper Structure (13 sections, 2 equations, 5 figures)

This paper contains 13 sections, 2 equations, 5 figures.

Table of Contents

  1. Introduction
  2. Results
  3. Discussion
  4. Conclusion
  5. Acknowledgements
  6. Funding.
  7. Author contributions
  8. Competing interests
  9. Data availability statement.
  10. Additional information

Figures (5)

  • Figure 1: Schematic of the experimental setup for the generation and coherent combination of optical vortices. The active control system, main amplifiers, off-axis holography unit, beam characterization system, and optical vortex generation method are highlighted in separate gray boxes. The components are labeled as follows: GS laser, gain-switched laser; ISO, isolator; Amp, amplifier; PM, phase modulator; PD, photodetector; VDL, variable delay line; CLS, cladding mode stripper; QWP, quarter-wave plate; HWP, half-wave plate; FF-ISO, free space Faraday isolator; HRM, high-reflective mirror; MHRM, motorized high-reflective mirror; VP, vortex plate; IBS, intensity beam splitter; BS, beam sampler; OSA, optical spectrum analyzer; FFM, flip-flop mirror; CCD, charged-coupled device.
  • Figure 2: (a) Optical spectra of the individual channels at $\sim$55 W and their coherent combination at 100 W average output power with a topological charge $\ell$ = 8. Inset: the normalized spectra over narrow spectral ranges. (b) Stability analysis of polarization and output power in the coherently combined OV with $\ell$ = 8. A total of 2000 samples were acquired with a time interval of 58 ms. The output power stability is represented as normalized output power relative to the mean value.
  • Figure 3: Experimental results of coherent beam combining of optical vortices. Intensity profiles of three distinct linearly polarized Laguerre–Gaussian beams with topological charges $\ell$ = 1, 5, and 8 are presented for two individual channels and their coherently combined outputs. Additionally, the reconstructed phase-intensity distributions and the corresponding combining efficiencies are displayed.
  • Figure 4: Mode purity and CBC efficiency assessment. (a) Mode content analysis of the individual channels of the OVs and the combined OVs. (b) Comparison between the experimentally achieved CBC efficiency of the OVs and the corresponding theoretical optimal values.
  • Figure 5: Analysis of technical limitations impacting CBC efficiency, with a focus on critical spatial misalignments: lateral (a), longitudinal (b) and angular (c).