Lithographic fabrication of large diffractive optical elements on a concave lens surface

Area of Science:

• Optics and Photonics
• Materials Science
• Nanofabrication

Background:

• Diffractive optical elements (DOEs) are crucial for advanced optical systems.
• Fabricating large-scale DOEs on curved surfaces presents significant alignment and uniformity challenges.
• Existing lithography techniques may struggle with precise pattern transfer onto non-planar substrates.

Purpose of the Study:

• To demonstrate a laser direct writing lithography technique for fabricating large DOE patterns on concave lenses.
• To achieve precise alignment and uniform photoresist coating on a large concave substrate.
• To establish a versatile method for creating continuous surface relief DOEs on various lens surfaces.

Main Methods:

• Utilized a laser direct writer for precise pattern fabrication on a concave lens surface.
• Optimized spin-coating parameters (spin rate, acceleration, photoresist viscosity) for uniform film thickness.
• Investigated the capability to write lines with widths ranging from 0.7 to 10 micrometers in a single pass.

Main Results:

• Successfully fabricated a computer-generated diffractive optical element (DOE) pattern on a concave lens with precise alignment.
• Achieved uniform photoresist film thickness on the large concave substrate.
• Demonstrated the ability to write square line profiles and a grating structure with controlled line widths.

Conclusions:

• The laser direct writing lithography technique is effective for fabricating large DOE patterns on concave lenses.
• This method offers precise control over pattern features and alignment on curved surfaces.
• The technique is adaptable for transferring continuous surface relief DOE patterns onto both convex and concave optical surfaces.