Witness Samples
Witness Samples for Thin Film Coating Verification: SSP, DSP, and Wedged Configurations
Cimcoop manufactures precision witness samples for thin film coating verification and process control. Available in single-side polished (SSP) for reflection measurements, double-side polished (DSP) for transmission measurements, and custom wedge angles to eliminate etalon effects. Substrates include in-house grown silicon and germanium, plus ZnSe, ZnS, CaF₂, sapphire, fused silica, and optical glass. Standard diameter is 25.4 mm (1"). Manufactured and packaged in a Class 10,000 cleanroom.
Before you commit production parts to the coating chamber, you verify on witness samples. These sacrificial test pieces confirm spectral performance, durability, and environmental resistance. They keep your coating runs accurate, repeatable, and traceable.
We manufacture witness samples from in-house grown Si and Ge crystals, plus a full range of IR and visible-spectrum materials. SSP for reflection, DSP for transmission, wedged to kill etalon effects. Matched to your spectrometer setup.
Configurations
Three Formats. Your Choice.
Transmission (DSP)
Double-side polished. Both surfaces optically finished for accurate spectral transmission data on your spectrometer.
Reflection (SSP)
Single-side polished. Ground back surface eliminates back-surface interference for clean reflection measurements.
Wedged
Custom wedge angles to kill etalon effects in coherent-source measurements. Standard and custom angles per your spec.
Technical Data
Specifications
Why It Matters
- Cleaned and packaged in our Class 10,000 cleanroom
- Material type and refractive index engraved for production traceability
- Same crystal boules and blanks as our production optics -- consistent material
- Full traceability and certs of conformity
- Spectral performance verified with in-house FTIR and UV-VIS
- ISO 9001:2015 certified process
- Custom dimensions, tolerances, and configurations on request
Materials
Available Substrates
Every IR and visible-spectrum material we work with. In-house Si and Ge crystal growing included.
Infrared Materials
- Silicon (Si) — grown in-house
- Germanium (Ge) — grown in-house
- Zinc Selenide (ZnSe)
- Zinc Sulfide (ZnS / Cleartran)
- Calcium Fluoride (CaF2)
- Sapphire (Al2O3)
- Chalcogenide glass
Visible / UV Materials
- UV Fused Silica
- Fused Quartz
- Schott optical glass (N-BK7, SF-series, etc.)
- Ohara optical glass (S-BSL7, S-FPL, S-LAH, etc.)
- Color filter glass
- Custom substrates on request
Applications
How They're Used
Coating Verification
Verify AR, HR, bandpass, and custom thin film performance before production parts hit the coating chamber.
Process Control
QC tokens in every coating run. Batch-to-batch consistency. Documented process stability over time.
Environmental Testing
Humidity, temperature cycling, salt spray. Measure coating durability under environmental stress per MIL-spec.
Related
Related Products
FAQ
Frequently Asked Questions
What is an optical witness sample?
A witness sample is a sacrificial test piece placed alongside production optics in a thin film coating chamber. It allows engineers to verify coating spectral performance, durability, and environmental resistance without risking production components.
What is the difference between SSP and DSP witness samples?
SSP (single-side polished) samples have one optically polished face and a ground back surface, used for reflection measurements. DSP (double-side polished) samples have both faces optically finished, used for accurate spectral transmission measurements.
Why use wedged witness samples?
Wedged witness samples eliminate etalon interference effects that occur in plane-parallel samples when using coherent light sources. The wedge angle prevents multiple reflections from creating interference fringes in spectral measurements.
Does Cimcoop grow its own silicon and germanium for witness samples?
Yes. Cimcoop grows single-crystal silicon and germanium in-house, ensuring consistent material quality and full traceability from ingot to finished witness sample.
Last Updated: March 2026
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