Improved control of nonlinear absorption advances all-optical signal processing

Current fiber telecommunication networks are hindered by bottlenecks arising from electronic processing of optically transmitted signals. Nonlinear optical devices, such as limiters and saturable absorbers, suffer from fundamental limitations of intensity-dependent multi-photon dissipation processes.

Eric Plum and colleagues demonstrated a new all-optical mechanism for controlling absorption of coherent light that can be used for signal processing. According to Plum, this approach could potentially provide all-optical solutions for telecommunications and data processing. It is ultra-fast and could be applied to decrease optical damage, increase data capacity of optical information channels, enable long transmission lines and transfer signals between different wavelength division multiplexing channels.

The team exploited the Kerr nonlinearity, an intensity-dependent optical phase shift in a material’s refractive index, to control the absorption of mutually coherent light waves interacting with a thin absorber. The team demonstrated all-optical intensity discrimination, power limiting, pulse restoration, pulse splitting and signal transfer between carrier wavelengths within a fiber circuit containing a plasmonic metamaterial absorber.

“This work shows how we can leave the limitations of conventional nonlinear absorption behind,” Plum said. “By exploiting the Kerr nonlinearity to control absorption of light in a thin film, it is possible to control absorption from 0 to 100 percent, in principle with 100 THz bandwidth.”

According to Plum, this approach allows nonlinear control of light dissipation within an ideal absorber from perfect transmission to perfect absorption. Future work could take this approach and miniaturize it for application in photonic integrated circuits.

Source: “Nonlinear control of coherent absorption and its optical signal processing applications,” by Angelos Xomalis, Yongmin Jung, Iosif Demirtzioglou, Cosimo Lacava, Eric Plum, D. J. Richardson, Periklis Petropoulos, and Nikolay I. Zheludev, APL Photonics (2019). The article can be accessed at https://doi.org/10.1063/1.5123547 .