Optimizing chromatic dispersion control at discrete wavelengths using dual-layer harmonic diffraction elements

Abstract

This paper presents a design approach for dual-layer harmonic diffraction gratings (DL-HDEs) focused on optimizing chromatic dispersion control at discrete wavelengths. We propose a method to achieve near-100 % diffraction efficiency at multiple separated wavelengths while ensuring minimal variation in their diffraction angles, thereby substantially reducing overall dispersion. Unlike traditional harmonic diffractive elements (HDEs) or multi-layer diffractive optical elements (MLDOEs) that suffer from significant chromatic dispersion, this dual-layer design delivers enhanced wavelength-specific performance by leveraging complementary material dispersion and structural optimization. Through independent simulations of the component itself in this study, the influence of other components and other optimization factors is excluded, the DL-HDEs exhibit stable diffraction angles across target wavelengths (dispersion coefficient <0.05°/μm) and concentrated energy distribution in focal plane spots, making them well-suited for multi-spectral imaging, laser systems, and other applications requiring precise wavelength control. This work provides a promising pathway for developing compact, high-fidelity optical systems in targeted spectral bands.