Wide-angled off-axis achromatic metasurfaces for visible light

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Metasurfaces offer unique optical properties but often face limitations in achromatic performance and wide-angle operation.
• Achieving simultaneous multiwavelength and wide-angle functionality in off-axis configurations remains a significant challenge in optical element design.

Purpose of the Study:

• To present a novel approach for constructing multiwavelength achromatic metasurfaces.
• To enable these metasurfaces to operate effectively in off-axis configurations with an ultra-wide incident angle range for visible light.

Main Methods:

• The metasurface is engineered by integrating multiple metallic nano-groove gratings.
• Localized gap plasmon modes are excited at specific resonance wavelengths to enhance diffraction for transverse magnetic polarization.
• A fixed ratio between resonance wavelength and grating period is employed to achieve achromatic diffraction.

Main Results:

• The metasurface demonstrates efficient diffraction of multiwavelength incident light into a single direction.
• Near-complete suppression of specular reflection is achieved across an ultrawide incident angle range (10° to 80°).
• A wide-angled off-axis achromatic flat lens was designed, focusing different wavelengths to the same position.

Conclusions:

• The proposed method provides a simple and effective route for designing off-axis achromatic flat optical elements.
• These elements are suitable for imaging and display applications, overcoming stringent angle requirements.
• The findings pave the way for advanced optical devices with enhanced angular and spectral performance.