When the refractive index of the dielectric is the geometric mean of for example, glass and air, a layer of dielectric one quarter of a wavelength thick will make what is called a quarter wave transformer that perfectly matches the air to the glass. That eliminates reflection at the impedance mismatch of glass and air because the phase of reflections from the two surfaces of the dielectric then cancel.says said:Why is dielectric material used for anti-reflective coating?
Dielectric materials are used for anti-reflective coating because they have a low refractive index, meaning they can reduce the amount of light reflected off a surface. This helps to minimize glare and increase the clarity and contrast of images.
Dielectric materials work by creating a thin layer on the surface of an object that has a different refractive index than the surrounding medium. This causes light rays to bend and cancel each other out, reducing the amount of light reflected off the surface.
Dielectric materials have a high transmittance, meaning they allow light to pass through with minimal reflection. They are also durable, chemically stable, and can be easily deposited onto a variety of surfaces, making them a practical choice for anti-reflective coatings.
Dielectric materials are typically applied using a process called physical vapor deposition, where a thin layer of the material is deposited onto the surface of an object. This can be done using techniques such as sputtering, evaporation, or chemical vapor deposition.
While dielectric materials are effective at reducing reflection, they are only useful for a specific range of wavelengths. If the coating is not designed for the specific wavelength of light that is being reflected, it may not be as effective. Additionally, dielectric coatings can also be sensitive to temperature and humidity, which can affect their performance.