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<p>This work presents a&#xa0;numerical investigation of second-harmonic generation (SHG) from ultrashort femtosecond laser pulses in gallium nitride (GaN) nonlinear photonic crystals with a&#xa0;periodically modulated second-order nonlinear susceptibility. A&#xa0;coupled-wave model is employed to simulate the spatiotemporal evolution of the fundamental and second-harmonic pulses, taking into account linear absorption, group-velocity mismatch, dispersive effects, and quasi-phase matching. The influence of these factors on the conversion efficiency and temporal pulse profiles is systematically analyzed.</p><p>The results demonstrate that linear absorption in GaN significantly limits the effective interaction length and reduces the achievable conversion efficiency in the femtosecond regime. Dispersive effects lead to a&#xa0;pronounced degradation of the conversion efficiency for shorter pulses and cause substantial temporal pulse distortion, including pulse splitting. In addition, the SHG process is shown to be highly sensitive to deviations of the domain length from the value required for quasi-phase matching, with even moderate fabrication errors resulting in a&#xa0;noticeable efficiency reduction. These findings highlight the critical role of dispersion management, absorption minimization, and precise domain engineering for the realization of efficient GaN-based femtosecond frequency converters.</p>

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Numerical analysis of femtosecond second-harmonic generation in periodically poled GaN crystals

  • 期刊论文

  • 发表日期：

    2026年5月6日

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  • O. I. Sabirov,
  • A. S. Ashirov,
  • U. K. Sapaev

摘要

This work presents a numerical investigation of second-harmonic generation (SHG) from ultrashort femtosecond laser pulses in gallium nitride (GaN) nonlinear photonic crystals with a periodically modulated second-order nonlinear susceptibility. A coupled-wave model is employed to simulate the spatiotemporal evolution of the fundamental and second-harmonic pulses, taking into account linear absorption, group-velocity mismatch, dispersive effects, and quasi-phase matching. The influence of these factors on the conversion efficiency and temporal pulse profiles is systematically analyzed.

The results demonstrate that linear absorption in GaN significantly limits the effective interaction length and reduces the achievable conversion efficiency in the femtosecond regime. Dispersive effects lead to a pronounced degradation of the conversion efficiency for shorter pulses and cause substantial temporal pulse distortion, including pulse splitting. In addition, the SHG process is shown to be highly sensitive to deviations of the domain length from the value required for quasi-phase matching, with even moderate fabrication errors resulting in a noticeable efficiency reduction. These findings highlight the critical role of dispersion management, absorption minimization, and precise domain engineering for the realization of efficient GaN-based femtosecond frequency converters.