Ultra-compact integrated photonic logic chip

Silicon photonics is a promising platform for on-chip communications, computing, and sensing but the heterogeneous integration of emerging photonic materials and near-infrared light sources on silicon remains challenging. Conventional systems separate lasers from optical processors but coupling external light requires additional phase modulators, polarization controllers, and alignment components. III–V lasers are widely used for on-chip light generation, but they demand stringent bonding, mode matching, and alignment. Although several studies have integrated III–V devices with silicon waveguides, many of them lack compact on-chip computing units.

 

Conventional processors based on directional couplers, Mach–Zehnder interferometers, or microring resonators have dimensions of tens of micrometres and require tens to hundreds of micrometres spacing to avoid crosstalk, limiting integration density and computational capacity. Advances in material engineering, heterogeneous integration, and compact optical design are therefore needed for high-performance, stable on-chip photonic systems.

 

In a paper published in Light: Advanced Manufacturing, a research team led by Professor Xiaoyong Hu at Peking University reports an ultra-compact integrated photonic logic chip for all-optical information processing. The team designed and fabricated a device comprising a III–V whispering-gallery-mode microlaser, four hybrid Bi₂Te₃–silicon microring resonators, and inverse-designed optical interconnects. By reducing the minimum spacing between functional components to only 1.5 μm, the architecture achieves a high level of functional and spatial integration.

 

Using an electrically driven packaged prototype, the researchers demonstrated 2-bit all-optical logic operation. The system integrates on-chip light generation, optical transmission, nonlinear modulation, and logic processing within a compact platform, providing a near-infrared implementation of an integrated all-optical logic circuit.

 

The operation of the chip is centred on four hybrid Bi₂Te₃–silicon microring resonators. The Bi₂Te₃ coating provides a strong nonlinear optical response, enabling the resonances of the microrings to be tuned optically. Pump–probe measurements further revealed femtosecond-scale transient dynamics, indicating the potential of the hybrid material platform for ultrafast optical modulation. Light generated by the on-chip microlaser is routed through the inverse-designed interconnects and coupled into selected hybrid resonators. By changing the electrical drive applied to the microlaser, different resonators are pumped, producing distinct optical output states that encode the 2-bit logic results.

 

The researchers summarised the design strategy as follows:

“We adopted three complementary strategies to address the key integration challenges. First, a III–V semiconductor whispering-gallery-mode microlaser provides on-chip light generation. Second, the integration of a nonlinear Bi₂Te₃ layer with silicon microring resonators enables efficient all-optical tuning without bulky electrode structures. Third, inverse design is used to optimise the interconnects between functional devices, substantially reducing the circuit footprint.”

 

They added:

“The circuit combines active and passive components to generate, transmit, and process optical signals on the same platform. The active section consists of the whispering-gallery-mode microlaser, whereas the passive section comprises the hybrid Bi₂Te₃–silicon microring resonators and inverse-designed interconnects, with a minimum component spacing of only 1.5 μm. Changing the drive current of the microlaser selectively pumps different resonators and produces distinct logic output states.”

 

Compared with previously reported integrated optical logic devices, this architecture combines three functions on a single platform: on-chip light generation, nonlinear-resonator-based logic processing, and inverse-designed ultra-compact optical routing. This approach addresses both functional integration and component density, rather than improving either aspect in isolation.

 

The demonstrated platform could provide compact building blocks for high-speed optical computing and communication systems. More broadly, the integration of III–V light sources, nonlinear photonic materials, silicon resonators, and inverse-designed interconnects offers a promising route towards photonic integrated circuits with substantially higher density, faster response, and more complexity.

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