Strategy for design of achromatic diffractive optical elements with minimized etch depths

Area of Science:

• Optics
• Optical Engineering
• Materials Science

Background:

• Diffractive optical elements (DOEs) are crucial for manipulating light.
• Achieving achromatic performance in DOEs, which is independent of wavelength, remains a challenge.
• Existing methods often require complex designs or limited spectral ranges.

Purpose of the Study:

• To develop an effective strategy for designing achromatic diffractive optical elements.
• To investigate the role of substrate dispersion in DOE achromatization.
• To optimize DOE performance for the near-infrared spectrum.

Main Methods:

• Utilizing a doublet of two holograms etched into different substrates.
• Implementing a strategy to select substrates considering both refractive index difference and dispersion.
• Introducing a phase shift corridor to broaden the operational spectral range.
• Applying the strategy to design an achromatic DOE for near-infrared wavelengths.

Main Results:

• Demonstrated that substrate dispersion, not just refractive index difference, is critical for optimal DOE achromatization.
• Developed a substrate selection strategy enabling minimum etch depths for holograms.
• Achieved excellent performance metrics (diffraction efficiency, nonuniformity error) over an increased spectral range.
• Successfully designed an achromatic DOE for near-infrared applications.

Conclusions:

• The presented substrate selection strategy effectively enables the design of achromatic DOEs.
• Considering substrate dispersion significantly improves DOE performance across a wider spectral band.
• The developed achromatic DOE is suitable for near-infrared applications, offering enhanced spectral performance.