High-diffractive-efficiency defocus grating for wavefront curvature sensing

Area of Science:

• Optics and Photonics
• Wavefront Sensing
• Diffractive Optics

Background:

• Wavefront curvature sensing is critical for optical system alignment and characterization.
• Existing methods may face limitations in efficiency or complexity.
• Phase gratings offer a promising route for advanced optical element design.

Purpose of the Study:

• To propose and characterize an optimal phase defocus grating for wavefront curvature sensing.
• To investigate a specific binary-phase-step design for enhanced performance.
• To experimentally validate the theoretical predictions of the grating's efficiency.

Main Methods:

• Theoretical computation of diffractive efficiency for a quantized, binary-phase-step defocus grating.
• Derivation and analysis of the optical transfer function.
• Fabrication of the optimized phase defocus grating.
• Experimental verification of diffraction efficiencies for the +/-1 orders.

Main Results:

• The proposed phase defocus grating is equidistantly quantized with a phase-step height of pi.
• Theoretical calculations predicted the diffractive efficiency.
• Experimental results confirmed high diffractive efficiencies for the +/-1 diffraction orders, averaging 38.08% and 40.36% respectively.

Conclusions:

• The developed phase defocus grating is optimal for wavefront curvature sensing.
• The binary-phase-step design with a pi phase-step height demonstrates high performance.
• Experimental validation confirms the practical utility and efficiency of the proposed grating.