Diffractive Optical Elements Made by Photopolymerisation: Phase Control, Surface Quantisation and Efficiency

Diffractive optical elements made by photopolymerisation encode optical phase in surface relief or discretised height levels, making phase-depth fidelity, quantisation, roughness and material index central manufacturing variables. This review distinguishes a resolved diffractive optical element from both refractive micro-optics and subwavelength metasurfaces. Two-photon and vat-photopolymer reviews provide the process context, while direct fabrication of multilevel Fresnel diffractive microlenses illustrates the coupling between step fidelity and focusing efficiency. Qualification is organised around measured relief depth, lateral registration of phase zones, refractive index at the operating wavelength, diffraction efficiency and unwanted-order power. A nominally correct profile can still lose efficiency through index error or roughness, while an efficiency deficit can arise from phase-depth bias, quantisation or alignment. The proposed framework therefore requires a measured phase model rather than efficiency alone.

ER-339 · Version 0.4.