Photonic Integrated Circuits (PICs) are microchips that integrate multiple optical components, such as lasers, modulators, waveguides, and photodetectors, onto a single semiconductor substrate to generate, manipulate, and detect light. Similar to electronic integrated circuits that process electrical signals, PICs process optical signals and are widely used in fiber optic communications, sensing, and signal processing. By integrating many photonic functions onto one chip, PICs improve performance, reduce size and power consumption, and enable high-speed data transmission in modern optical networks and data centers.