Photonic Integrated Circuit Components

Key Takeaways

• Photonics is the branch of study that controls and manipulates photons for various operations. 

• Photonic integrated circuits are fabricated on standard semiconductors, compound semiconductors, nonlinear crystal materials, and dielectric materials.

• Photonic integrated circuit components are incorporated for power handling, polarization handling, or to maintain active interaction between the electrical and magnetic fields with the optical field. 

Photonics is a field of electronics engineering where light is utilized for operating devices or developing technology

Photonics is a field of electronics engineering where light is utilized for operating devices or developing technology. Photons carry energy in photonics. Photonic integrated circuits are used for signal processing, computing, and amplification as well as the generation, detection, and manipulation of photons. Photonic integrated circuit (PIC) components include lasers, optical amplifiers, waveguides, modulators, demodulators, photodetectors, etc. 

Photonics

Photons are massless particles that have full integer spin. They are the smallest units of light.

Photonics is the branch of study that controls and manipulates photons for various operations.

In photonics, photons are generated and utilized in a controlled environment. Among the kinds of radiant energies photons produce, photonic applications utilize the visible and infrared bands of the electromagnetic spectrum.

Photonic Integrated Circuits

Photonic integrated circuits (PIC) are chips containing photonic components that operate with photons. Light is injected into photonic integrated circuits to drive the components. All operations are controlled by light. Lasers are a common light source in photonic integrated circuits. Other components are used for the detection, manipulation, and amplification of photons. 

Components

In photonic integrated circuits, photons travel through optical components. Some photonic integrated circuit components are waveguides, polarizers, lasers, phase shifters, etc.

Materials Used

Photonic integrated circuits are fabricated on standard semiconductors, compound semiconductors, nonlinear crystal materials, and dielectric materials. Some of the materials used in the fabrication of the photonic integrated circuits are:

1. Indium Phosphide (InP)
2. Gallium Arsenide (GaAs)
3. Silicon Nitride (SiN)
4. Lithium Niobate (LiNbO3)

The significance of PICs is growing as electronic ICs reach their maximum integration capacity. Under these circumstances, the potential of photonic integrated circuits is utilized in data communications, autonomous vehicles, aerospace aeronautical applications, etc.

Advantages

• Miniaturized circuits 
• Fast operations or higher speed than electronic ICs 
• Low heat generation
• Large integration capacity
• Compatible with almost all existing technologies in ICs
• Low cost and large volume manufacturing possible

Applications

Photonic integrated circuits find broad applications in:

• Data communications
• Automotive industry
• Astronomy
• Agriculture
• Biomedical equipment
• Defense and aerospace industry

Photonic Integrated Circuit Classifications

Photonic integrated circuits are classified into four groups based on their function, integration level, and substrate materials. The classifications are illustrated in the figure below.

Photonic Integrated Circuit Components

Photonic integrated circuit components are incorporated for power handling, polarization handling, or to maintain active interaction between the electrical and magnetic fields with the optical field. Let’s discuss a few of the photonic integrated circuit components here.

Semiconductor Lasers

Semiconductor lasers generally consist of an amplifying medium placed inside a resonant cavity. The semiconductor laser is a common light source in photonic integrated circuits. In semiconductor lasers, the origin of the coherent optical emission is due to the stimulated transition from the higher energy conduction band to the lower energy volume band in semiconductors.

Advantages 

• Small size means easy integration
• Direct pumping is possible by low-power electric current
• Efficient at converting electric power to light 
• Able to modulate the output by direct modulation
• Monolithic integration with bipolar transistors, optical components, etc. to form photonic integrated circuits

Optical Amplifiers

In photonic integrated circuits, the light is subjected to losses such as insertion loss, branching loss, propagation attenuation, etc. For restoring power levels, optical amplification is a must. In  semiconductor optical amplifiers, the gain or amplification is achieved by injecting an electric carrier into the semiconductor to provide population inversion. The self-oscillation of the optical amplifier is prevented by eliminating the cavity reflection. Usually, antireflection coating and angle cleaving methods are employed to prevent self-oscillations. Semiconductor optical amplifiers are electrically pumped by injecting current.

Advantages

Optical semiconductor amplifiers provide significant gains in a short semiconductor chip of less than 400m. The table below gives an overview of some other photonic integrated circuit components.