Novel Microscale Mechanical Switch of Light on a Silicon Chip
Optical fibers can connect your home to the internet at 100 times faster speed than electrical cables because each glass optical fiber can carry many channels using different color of light. This is possible because, unlike electrical currents, light in different colors does not like to interfere with each other. Recently, in the journal Nature Communications, Professor Mo Li’s group in the Electrical and Computer Engineering Department at the University of Minnesota reported a new device which allows one optical signal to directly control another optical signal of a much higher power level so that signal amplification is achieved.
The device was fabricated in the Nanofabrication Center (NFC) using tools such as the new Vistec EBPG-5000+ e-beam lithography system and the Oxford PlasmaLab 100 etcher. In the device there are two optical waveguides, each carrying an optical signal. Between them is an optical resonator in the shape of a microscale donut with very high optical quality, which means light can circulate thousands of rounds in it before leaking out. Utilizing this resonance effect, the optical signal in the first waveguide is significantly enhanced and generates a very strong optical force on the second waveguide. The second waveguide is released from the substrate so that it moves when a force is applied on it. The mechanical motion of the waveguide alters the transmission of the optical signal it carries. When the first optical signal, which generates an amplified force on the second waveguide, is modulated, it controls the position of the second waveguide. If light of a different color with a higher power level is input in the second waveguide, the information is thus transferred from one color of light to another color with amplified amplitude. Such a device is a direct analogy to electromechanical relays but operates completely with light.
The optical relay device currently operates at 1-10 MHz and can be improved to 1GHz so it is sufficiently fast for radio-frequency photonics and sensor applications. Funding support of the project is provided by the College of Science and Engineering and the Young Investigator Program (YIP) of the Air Force Office of Scientific Research (AFOSR).