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Optical Filters


Plasma Quest Optical Filters

Plasma Quest Ltd has developed a wide range of coating materials suitable for use in optical filters using the proprietary HiTUS thin film sputter deposition equipment. 

Optical filters are typically components with either a wavelength-dependent transmission or a wavelength-dependent reflectivity.  The simplest optical filter is the absorptive filter, where select wavelengths of light are absorbed and the rest transmitted.  More complex interference filters exhibit wavelength-dependent reflection and transmission.  Dielectric and dichroic mirrors are examples of interference based filters.  The mirrors usually consist of alternating thin layers of two transparent dielectric materials.

A wide range of dielectric films can be reactively sputtered at high rates (e.g. SiO2 > 55nm/min from a 4” target) using the HiTUS thin film sputter deposition equipment.  The high level of densification produces thin films with very little argon inclusion (<1%), very smooth interfaces between layers and refractive indices close to bulk.  Materials include SiO2, Al2O3, TiO2, Nb2O5, Ta2O5. 

PQL’s system allows accurate deposition of optical filters consisting of multi-layer stacks.  The HiTUS system uses a multiple-target holder which provides the capability to repeatedly and reliably deposit identical alternating layers of differing materials, without having to break the vacuum.  Coupled with a menu driven PLC, one-touch batch process control is easily achieved.

  • Film properties are maintained at varied deposition rates
  • The process is very stable and is repeatable run to run
  • Dielectrics are reactively sputtered from metallic targets in most cases, leading to the densification of the deposited films
  • Expensive feedback control is not necessary.
  • Very smooth interfaces


If a material can be sputter deposited, it can be coated using the Plasma Quest approach. Please

Contact Us for a discussion about how our coating service can solve your problems. We look forward to speaking with you.



Download printable version of Optical Filters.pdf

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