Ateneo KISLAP

Photonic Integrated Circuits

Using light to transmit data

What are integrated circuits?

Integrated Circuits (ICs) are assemblies of related components that act as a single unit. In electronics, ICs are tiny chips with resistors, transistors, capacitors, and other components where an electric current flows. These chips function as timers, oscillators, and logic gates, and are what make smartphones, televisions, and all electronic devices possible.

What about photonic integrated circuits?

A Photonic Integrated Circuit (PIC) is analogous to electronic ICs. Instead of an electric current and the aforementioned components, a PIC utilizes light and components such as waveguides, polarizers, and phase shifters.

PICs are light-dependent. Thus, for a PIC to work, a laser source injects light that then passes through the PIC’s different components. A waveguide, the PIC component equivalent to a resistor, directs and confines the propagation of electromagnetic waves. A polarizer is a filter that permits the propagation of waves polarized or oriented in a certain direction and blocks waves with other orientations. A phase shifter changes the transmission phase (i.e., the relative “location” or “timing” of a point on a wave) of a wave signal. 

Figure 1. Computer-Rendered Photonic Integrated Circuit Diagram

How can we make use of PICs?

Photonics and PICs have various applications in different industries. The most common applications are in Information and Communication Technology (ICT) and medical technology. In ICT, photonics makes internet connections with more bandwidth and higher speeds possible through “ultrafast chips” and fiber optic cables. The use of light makes data transmission faster and more efficient. In medicine, PICs are used to investigate medical conditions through different wavelengths of light. With photonic devices, diagnosis can be made with non-invasive tools (i.e., not requiring the device to enter the body).

References

[1] Editors of Encyclopaedia, waveguide. Encyclopedia Britannica. 2011.

[2] “IT & Communications,” Photonics Application Week. 2022.

[3] R. Paschotta. “Photonic integrated circuits. Photonic integrated circuits, explained by RP Photonics Encyclopedia; planar lightwave circuits, PIC, PLC, integrated optics, applications.” 2022.

[4] University of Rhode Island. “Introduction to phase.” Discovery of Sound in the Sea. 2021.