Programmable PIC tunes optical delay
Researchers in South Korea have proposed a reconfigurable photonic integrated circuit that can dynamically control optical delay, bandwidth and frequency response on a single silicon nitride platform.
Researchers at Seoul National University and the University of Seoul have developed a programmable photonic circuit architecture designed to control how optical pulses propagate through an integrated device.
The approach is based on coupled-resonator-induced transparency (CRIT), a technique in which interacting optical resonators create a narrow transmission window while introducing a controlled delay to the passing light.
Conventional CRIT devices typically have fixed optical characteristics determined by their geometry and coupling configuration during fabrication. Changing the delay, transmission bandwidth or operating frequency can therefore require a different device design.
The researchers instead propose incorporating two tunable loop couplers into the resonator network, enabling the interaction between the circuit's bright and dark optical modes to be adjusted after fabrication.
Numerical modelling showed that the architecture could dynamically alter the transmission bandwidth and optical delay while also modifying the frequency characteristics of the transmitted signal.
This programmability could allow a single photonic circuit to perform several functions that would otherwise require separate components, including adjustable delay, filtering, optical buffering and frequency conversion.
The team modelled the architecture using a silicon nitride photonic integrated circuit platform and carried out three-dimensional electromagnetic simulations to investigate its tolerance to practical fabrication and operating effects.
The simulations considered material losses, resonator variations, backscattering, coupling deviations, phase errors and thermal crosstalk between neighbouring components.
According to the researchers, the circuit continued to operate under these non-ideal conditions, suggesting that the architecture could potentially be implemented using existing photonic fabrication processes.
Potential applications include optical communications, signal synchronisation and photonic computing systems, where precise control over the arrival time of multiple optical signals is increasingly important.
“This research is significant in that it proposes a new design principle that allows the flow of light within photonic integrated circuits to be reconfigured as needed, greatly enhancing design flexibility,” said Namkyoo Park, professor at Seoul National University.
The work currently remains at the theoretical and simulation stage. The researchers plan to move towards device fabrication and experimental validation, with the longer-term goal of extending the approach to larger programmable photonic circuits.
