Contents
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Mirrors in Optics and Photonics
Introduction to Mirrors
A mirror is an optical device that reflects light, with the reflection being of a specular type where the angle of reflection equals the angle of incidence. Reflective diffusers and diffraction gratings are not considered mirrors. Mirrors can have flat or curved surfaces, with curved mirrors having focusing or defocusing properties.
Properties of Mirrors
Mirrors have various properties such as reflectivity, which is the percentage of optical power reflected, and reflectivity bandwidth, which is the range of wavelengths over which the mirror exhibits high reflectivity. The reflection phase and surface shape are also important properties of mirrors.
Types of Mirrors
Metal-coated Mirrors
Metal-coated mirrors are commonly used in households and optics. They can be backside mirrors (with a glass substrate) or first surface mirrors (directly coated). Advanced versions have dielectric layers for enhanced reflectivity and protection.
Dielectric Mirrors
Dielectric mirrors contain thin dielectric layers that enhance reflectivity. They are commonly used in laser technology and optics, with designs like Bragg mirrors offering high reflectivity at specific wavelengths.
Dichroic Mirrors
Dichroic mirrors have different reflection properties for two wavelengths, making them useful in applications like nonlinear frequency conversion.
Curved Mirrors
Curved mirrors, with spherical or parabolic surfaces, are used for focusing or imaging applications in optics and photonics. Off-axis parabolic mirrors are often used for tight focusing.
Deformable Mirrors
Deformable mirrors allow control of the surface shape and are used in adaptive optics for correcting wavefront distortions.
Variable Reflectivity Mirrors
Variable reflectivity mirrors have reflectance that varies across their surface and are used in lasers with unstable resonators and as variable optical attenuators.
Special Function Mirrors
Phase-retarding Mirrors
Phase-retarding mirrors introduce a phase difference for polarized components of a beam and can be used for polarization conversion.
Absorbing Thin-film Reflectors
Absorbing thin-film reflectors are designed to reflect one polarization while absorbing another, useful in applications like optical isolators.
Mirrors in Fiber Optics
In fiber optics, mirrors are used to reflect light back into the fiber. Fiber loop mirrors and other types of fiber reflectors serve various purposes in fiber optic systems.
Conclusion
Mirrors play a crucial role in optics and photonics, with various types catering to different applications. Understanding the properties and types of mirrors is essential for designing optical systems and devices.
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