Optomechanical signal processing through acoustic-wave interference on a silicon chip

Optical signal processing using the phase, intensity, or polarization of light is a rapidly growing field along with the development of nanophotonics process technology. The photonic integrated circuit for optical signal processing aims to operate light generation, transformation, control, and detection on a single chip and is attracting considerable interest as a pioneering research area. Recently, a research team led by Professor Heedeuk Shin of the Department of Physics at POSTECH has successfully demonstrated an optical-wave signal that can be amplified or canceled using optically driven acoustic waves on a silicon chip for the first time in the world.

Optical signal processing has an advantage in that it generates less heat than electron signal processing and can exploit the high speed of light. Recently, optical signal processing technology using Brillouin scattering, in which acoustic waves scatter light, has been demonstrated in nanophotonic structures. However, since the research findings so far have only measured simple acoustic wave generation and light scattering, it is necessary to show the feasibility of optical signal processing through optically driven acoustic wave control for applications in signal processing and sensing. 

To this, the POSTECH research team proposed an active optical signal processing method using the interference of acoustic waves generated on a silicon chip. First, three optical waveguides, thinner than one hundredth the thickness of a human hair strand, were fabricated side by side on a silicon chip via nano processing. Two acoustic waves were interfered with by generating acoustic waves in two optical waveguides using optical forces³ and controlling the time for them to reach the third optical waveguide. Through this, the research team observed the amplification and cancelation of a microwave signal between constructive and destructive interferences of acoustic waves on a silicon chip with a contrast greater than 10,000 times and developed it further to demonstrate that the intensity of a pulse signal can be adjusted for the first time in the world.

"This is the first demonstration of optical signal processing using acoustic-wave interference in a nanostructure,” remarked Professor Heedeuk Shin. On the significance of the study, he explained, “Through this research, we present a new direction for optical signal processing and sensing technology, and look forward to new applications in the optomechanical system."

The findings from this study were published in Nano Letters, an internationally renowned academic journal.

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