A team of researchers from Nanjing University has developed a new approach to photonic integration using a gallium-nitride (GaN)-on-silicon platform. This approach involves combining various active and passive optical components, such as a light source, modulator, photodiode, waveguide, and splitter, on a single photonic integrated circuit chip. What sets this approach apart is that all active devices are built on the same structure, reducing complexity and cost.

Schematic diagram of the proposed photonic integrated chip.

While InP-based photonic integration is commonly used, it has limitations in terms of yield and substrate size. Monolithic silicon photonics, on the other hand, offer excellent passive performance and compatibility with complementary metal oxide semiconductor (CMOS) fabrication but lack a light source. The GaN-on-silicon platform addresses these limitations.

The researchers designed the circuit chip using GaN-on-silicon technology and III-nitride epitaxial layers. They extensively tested the chip to validate its effectiveness. The results showed that applying a higher reverse bias voltage to the modulator increased light absorption, resulting in distinct modulation effects observed in the receiver's photocurrent changes. The chip also demonstrated negligible cross-talk and adequate isolation between the light source and modulator on the same waveguide.

The researchers successfully demonstrated simultaneous transmission of two types of data using direct and indirect modulations within a single light path. They also validated the data transmission and processing using UV light. The adoption of a multifunction multiple quantum-well (MQW) structure helped overcome compatibility issues and reduce fabrication complexity.

The research team believes that their approach, along with advancements in III-nitride etching accuracy, holds great potential for next-generation photonic integration. They particularly see promising applications in the sensing field, where high integration density is not a critical requirement.