Scaling up multispectral color filters with binary lithography and reflow (BLR)

Area of Science:

• Optics and Photonics
• Materials Science
• Microfabrication

Background:

• Miniaturized spectrometers and multispectral imaging demand increased numbers of optical filters.
• Sequential filter fabrication processes are often cost-ineffective for mass production.

Purpose of the Study:

• To introduce a novel, cost-effective method for fabricating multiple distinct microscopic transmission filters.
• To demonstrate precise control over dielectric layer thickness using a modified lithography technique.

Main Methods:

• Utilized standard binary lithography followed by a post-development reflow process to create height variations in polymeric resist.
• Achieved minimum feature sizes of 0.6 μm.
• Incorporated resulting transparent polymeric films into Fabry-Perot cavities with thicknesses ranging from 90 to 230 nm.

Main Results:

• Successfully produced at least 16 distinct filters from a single lithographic step.
• Demonstrated control of dielectric layer thickness down to approximately 15 nm.
• Enabled transmittance across the visible spectrum.

Conclusions:

• The binary lithography and reflow (BLR) process offers a cost-effective alternative for fabricating microscopic transmission filters.
• This technique is suitable for applications requiring precise thickness variations across a substrate.
• The BLR process supports the development of advanced optical devices like miniaturized spectrometers.