Federico Capasso, an applied physicist at Harvard University and Daniel Lopez, group leader of nanofabrication and devices at Argonne National Laboratory, are developing a system in which motion capabilities like fast scanning and beam steering are added to metalenses.
Capasso and Lopez claim to have developed a device that integrates mid-infrared spectrum metalenses onto MEMS.
"Dense integration of thousands of individually controlled lens-on-MEMS devices onto a single silicon chip would allow an unprecedented degree of control and manipulation of the optical field," Lopez said.
The metasurface lens was formed using standard photolithography techniques on a silicon-on-insulator wafer with a 2-micron-thick top device layer, a 200-nanometer buried-oxide layer and a 600-micron-thick handle layer.
The flat lens was then placed onto a MEMS scanner, essentially a micromirror that deflects light for high-speed optical path length modulation. The team aligned the lens with the MEMS' central platform and fixed them together by depositing small platinum patches.
"Our MEMS-integrated metasurface lens prototype can be electrically controlled to vary the angular rotation of a flat lens and can scan the focal spot by several degrees," Lopez continued. "This proof-of-concept integration of metasurface-based flat lenses with MEMS scanners can be extended to the visible and other parts of the electromagnetic spectrum, implying the potential for application across wider fields, such as MEMS-based microscope systems, holographic and projection imaging, light detection and ranging scanners and laser printing."
When electrostatically actuated, the team said the MEMS platform controls the angle of the lens along two orthogonal axes, allowing the scanning of the flat lens focal spot by about 9 degrees in each direction. The researchers estimated that the focusing efficiency is about 85%.
"Such metalenses can be mass produced with the same computer-chip fabrication technology and in the future, will replace conventional lenses in a wide range of applications," Capasso added.
