What are Bragg mirrors used for?

Bragg Mirrors: An Overview

Bragg mirrors, also known as distributed Bragg reflectors (DBRs), are a type of optical mirror used in various applications to reflect specific wavelengths of light while allowing others to pass through. They are constructed from multiple layers of alternating materials with different refractive indices. The thickness of each layer is precisely controlled to be a quarter of the wavelength of light that the mirror is designed to reflect.

Principle of Operation

The operation of Bragg mirrors is based on the principle of constructive interference. When light waves reflect off the different layers, the waves that are in phase with each other combine to enhance the reflection at the desired wavelength, while those that are out of phase cancel each other out. This selective reflection is what makes Bragg mirrors particularly useful in optical engineering.

Applications

• Laser Resonators: Bragg mirrors are commonly used in the construction of laser resonators, where they serve to reflect specific wavelengths back into the lasing medium, thereby enhancing the efficiency and selectivity of the laser output.
• Optical Filters: They are also employed as optical filters in telecommunications to selectively transmit or reflect different channels of light, thus enabling wavelength division multiplexing (WDM).
• Sensors: In sensor technology, Bragg mirrors can be used to create highly sensitive devices for measuring strain, temperature, or pressure by detecting shifts in the reflected wavelength.
• Photonic Crystals: They form an integral part of photonic crystals, which are used to control and manipulate the flow of light in photonic devices.

Advantages

Bragg mirrors offer several advantages, including high reflectivity, the ability to precisely control the reflected wavelength, and the potential for integration into compact and complex optical systems. Their versatility and efficiency make them an essential component in the field of optical engineering.