The laser pulses were focused in a microscope directly into liquid photoresist (resting either on a glass substrate or on the tip of an optical fiber).
After exposure, the unexposed photoresist was washed away with a solvent, leaving behind the hardened transparent polymer. Doing so they were able to design complex optical lens stacks, including common spherical lenses, but also paraboloids or aspherical lenses.
PhD student Timo Gissibl in the group of Prof. Harald Giessen at the 4th Physics Institute printed micro-objectives with a diameter and height of only 125μm, directly on the tip of optical fibres, which could enable miniaturized endoscopes.
Timo Gissibl also printed optical free form surfaces and miniature objectives directly onto CMOS image chips, creating an extremely compact sensor with integrated optics.
The researchers hope that using such optics, smaller and lighter cameras could be designed for drones and robots.
The micro-lenses are also applicable to illumination systems including LED applications where light need to be focused in a particular direction. With this additive manufacturing approach, the researchers claim that physical prototyping could take less than a day, from concept idea to the finished product.
The project was supported by Baden-Württemberg Stiftung within the project “Spitzenforschung (cutting-edge research)”. The highly precise femtosecond 3D printer was built by German startup Nanoscribe (founded by researchers from KIT).
Visit the University of Stuttgart at www.physik.uni-stuttgart.de