Introduction to Optical Coating Technology for Optical Filters

Evaporative deposition coating technology

In the evaporation deposition coating technology, the source material in the vacuum chamber is heated or evaporated by an electron beam, and the vapor condenses on the optical surface. During the evaporation process, optical coatings with uniform thickness can be obtained by precisely controlling heating, vacuum pressure, substrate positioning, and rotation. Evaporation is a relatively mild technology that can cause the coating to become loose or porous. This loose coating has water absorption, which changes the effective refractive index of the film, resulting in a decrease in performance. Ion beam assisted deposition can enhance the evaporation coating, where the ion beam is aimed at the substrate surface. This increases the adhesion between the source material and the optical surface, generates greater stress, and makes the coating denser and more durable.

Ion beam sputtering (IBS) coating technology

When the ion beam is sputtered, the high-energy electric field accelerates the generation of the ion beam, which gives the ions a large amount of kinetic energy. When colliding with the source material, the ion beam splashes out atoms of the target. These sputtering target ions (due to the influence of ionization zones, atoms are converted into ions) also have kinetic energy and produce dense thin films when in contact with optical surfaces.

Plasma Sputtering Coating Technology

Plasma sputtering is a general term for a series of technologies, such as advanced magnetron sputtering and plasma sputtering. Regardless of the technology, including the generation of plasma, ions in the plasma are accelerated into the source material, collide with loose energy source ions, and then sputtered onto the target optical element. Although different types of plasma sputtering have their unique characteristics, advantages, and disadvantages, this coating technique is much smaller than other coating techniques discussed in this article.

Atomic layer deposition coating technology

Unlike evaporation deposition, the source material for atomic layer deposition does not need to evaporate from a solid, but exists directly in the form of a gas. Although this technique uses gas, high temperatures are still required in a vacuum chamber. In the ALD process, the gas precursor is transmitted through non overlapping pulses, which are self limiting. This process has a unique chemical design, with only one layer adhered to each pulse, and there are no special requirements for the surface geometry of optical components. Therefore, this process allows us to control the coating thickness and design, but it will reduce the deposition rate.

coating process

Different coating deposition techniques have their own advantages and disadvantages, and Ruicheng Optoelectronics can use different deposition techniques to provide customer service.