Optical precision filters

Spectroscopy and telecommunications

  • Steep edges    
  • Precisely defined transmission spectra
  • Particle free

Precision sputtering coating system for interference optical applications


A lot of modern measurement methods are based on optical methods, as are large parts of the telecommunications industry. In these applications, optical filters need to remove individual wavelengths from a light beam (notch filter), allow only defined wavelengths to pass through (band-pass filter) or switch from reflection to transmission at a certain wavelength (edge filter). Interference-optical stacks of thin, dielectric layers with alternating high and low refractivity act as optical filters.

Requirements for the system

The system is designed to produce optical filters on flat substrates with a diameter of up to 200 mm. As precision filters, they need to have a reproducible transmission spectral profile with particularly steep edges and low scattering rates. From a technological perspective that means: Stacks of 50, 100 or more layers need to be deposited while maintaining a precise thickness for each individual layer and depositing the layers evenly over the entire substrate with a thickness non-uniformity of less than +/- 1%. Optically relevant particles are to be avoided in the process and the system will of course need to be able to process recipes fully automatically and produce a high output.

Solutions to requirements

FHR.Star.500-EOSS® is an advanced development of the Enhanced Optical Sputtering System (EOSS®) developed jointly with the Fraunhofer Institute for Surface Engineering and Thin Films. It is the most advanced product currently available on the market for producing interference-optical filters.

The special features of this system are:

  • Outstanding reproducibility  
  • Sputter-up process for the lowest particle density  
  • Optimal layer formation through dual bipolar sources  
  • Highest material utilization and longest target service life using rotary targets   
  • Highest layer thickness precision due to in-situ broadband optical monitoring (MOCCA+®)   
  • A design that is uncompromisingly configured for production processes

System control is coupled with an optical monitoring system for precise monitoring of the layering progress. It continuously detects the transmission spectrum of the developing layer on the substrate (test substrate) in-situ. Optical monitoring is based on the MOCCA+® measuring system and software environment (Modular Optical Coating Control Application) developed by the Fraunhofer IST. The measuring system functions in a wavelength range from 360 nm to 1680 nm in the UV-VIS-NIR window.


Deposition of optical multilayers

The system is designed for loading and unloading in cleanroom

Key features



Machine dimension

5.0 m x 5.0 m x 3.2 m, weight: 12 t

Number of process stations


Substrate size

Diameter: 200 mm (EOSS 500), 300 mm (EOSS 600), weight: 10 kg max.

Substrates pro carrier

12 x 8" or 12 x 6" or 24 x 4", other dimensions on request

Magazine load lock

20 carrier positions

Layer-Thickness uniformity error

+/- 0.25 %

Layer-Thickness measurement

In-situ broad-band monitoring (UV-VIS-IR)

Dr. Ronny Kleinhempel - Segment Manager Optics

Contact EOSS® Systems

Dr. Ronny Kleinhempel

+49 35205 520-172 sales[at]fhr.de