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.


If you would like to discuss your trial requirements, obtain costing, turnaround times, or for any other questions, we would love to hear from you.