Explain the concept of a Bragg reflector.

A Bragg reflector is an optical device specifically designed to reflect certain wavelengths of light through the principle of constructive interference. This device typically consists of alternating layers of materials with different refractive indices, which create a periodic structure. When light encounters this layered architecture, specific wavelengths will interfere constructively, meaning that they reinforce each other, resulting in strong reflection. This selectivity in reflection allows Bragg reflectors to be finely tuned to particular wavelengths, making them highly useful in applications such as telecommunications, lasers, and optical coatings.

The other options do not accurately describe the function of a Bragg reflector. A Bragg reflector does not reflect all incoming light, nor does it act as a filter that absorbs certain wavelengths, and it is not used primarily to guide light like in fiber optics. Its focus on specific wavelengths and the dependence on interference phenomena are what make it distinct from these other optical devices.