High-Numerical-Aperture Microlenses Fabricated by Soft Lithography

In the March 14 issue of Applied Physics Letters, researchers at Nanyang Technological University in Singapore and Shenzhen University in China describe the use of soft lithography to produce microlenses in hybrid SiO₂/TiO₂ sol-gel glass, with numerical apertures of 0.3 to 0.5. The technique may have applications in the fabrication of optical elements for telecommunications, optical memory and imaging.

The researchers created a master by heating a patterned photoresist so that it flowed to form an array of hemispheres that could be used as planoconvex lenses. They coated this with polydimethylsiloxane, which, when cured, formed an elastomeric negative mold. To reproduce the master array, they pressed the mold onto a photosensitive sol-gel layer, which they cured under UV radiation to form hybrid SiO₂/TiO₂ sol-gel glass.