20
Oct
Optical Interference

Glass Coatings

Optical coatings are made up of thin film layers, which together create interference that enhances the transmission, or reflection optically manipulated light. How these coatings perform depends on the number of layers, and the thickness of each layer. What is also important is the resultant refractive index difference at the layer interfaces.

 

The optical coatings most commonly used nowadays are anti-reflection (AR) coatings, high reflective (Mirror) coatings, beam splitter coatings, and filter coatings. The first of these types is seen in most refractive optics, and work to drive up throughput and eliminate ghosting. Mirror coatings, meanwhile, work to boost the reflectance at any single wavelength, or through a predefined range.

 

Beam splitter coatings are used to split the incoming light beams into several outputs. Filter coatings find use in a large number of industry applications, and basically produce effects such as transmitting, reflecting, absorbing, or attenuating light.

 

Optical coatings are made out to affect a specific angle and polarization of light. This means that, say, if it were meant for a 0° incidence angle, then it won’t work with a 45° angle of incidence, at least not as well as specified. In the same way, most coatings being designed for light which is randomly polarized, using S-polarized or P-polarized light will diminish the results, sometimes far below what the specifications stated.

 

Optical coatings are manufactured by adding thin layers of dielectric and metallic materials like Ta2O5 and/or Al2O3, typically in QWOT or HWOT specifications. These films are alternately placed among layers of high and low indices of refraction, so as to achieve the desired interference effects.

 

Coating effects

 

Optical Coatings

Optical Interference

Coatings dictate how and how much light is reflected and transmitted through optical interference. If you have two beams moving in via coincident paths and with matching phases, the spatially located wave peaks will also match, adding up to produce greater amplitude in the resulting light. However, when these beams are out of phase, the overlay will cause a subtractive effect at all the peaks and bring down the resulting amplitude. These are both interference effects, brought about through the use of the specially coated glass.

 

That was an overview of how optically coated glass functions. These various effects find use in many industrial applications such as projector glass, building windows, storefront, and museum displays, etc. get in touch with our experts to learn more.

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