News Article

Fiber Optic Center Introduces High Refractive Index Coating


Coating can improve performance of devices including optical sensors, integrated optical circuits and LEDs

The Fiber Optic Center (FOC), an international distributor of fibre optic components, equipment and supplies, has introduced a 'High Refractive Index Coating, AngstromLink AL-2264.

The performance of many solid-state devices including emissive displays, optical sensors, integrated optical circuits and LEDs can be improved by applying a transparent high refractive index coating.

According to FOC, the product, AL-2264, is an optical polymer dissolved in an evaporative solvent, can be applied by simple methods, i.e. dip, spin coating, drawdown, printing, etc. Upon drying it creates a hard, durable, polymer coating with a refractive index of 1.64. This polymer contains no metals, and the product contains no nanoparticles. The standard concentration leaves behind an approximately 20 μm layer coating thickness (using a single dip coating process). Coating thickness is easily reduced by diluting the standard concentration with the compatible solvent. The solvent is easily removed by baking at 100°C for 15 minutes.

Optically clear, high refractive index coatings can be used to improve the performance of light gathering/dispersing devices. Many solid state optical devices, i.e. imaging/optical sensors, emissive displays, LEDs, are made of light emitting semiconductors with significantly higher refractive indices (>2) than air (1.0). Light is partially reflected when it encounters a sudden difference of refractive index. Light transmission at such boundaries is improved with a layer of an intermediate refractive index material, thus improving the optical efficiency of the device "“ effectively raising the numerical aperture (NA) of the optical system.

For semiconductors and air, that desirable refractive index is in the >1.6 range. Additionally, in this case, the "˜air' side of the coating directly contacts the environment and must be protective: hardness and durability are required; chemical resistance is a plus.

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