Evaporative Coatings
Coating recipes designed for polymer, not borrowed from glass.
In-house e-beam IAD coating with a process window built around the polymer's thermal limit. The four failure modes that decide whether a coating ships — outgassing, adhesion, thermal budget, and CTE mismatch — are the four things our recipe development is organised around.
AR · BBAR · Dichroic · Beamsplitter · Mirror
Coating types
Stack families that cover most polymer-optic programs.
- Anti-reflective (AR)
- Single-band V-coats and broadband AR (BBAR) tuned to the optical envelope of the program — visible, NIR, SWIR, or hybrid bands. Designed against the polymer's index dispersion, not borrowed from a glass recipe.
- Broadband AR (BBAR)
- Wide-band reflectance suppression for imaging stacks where the source or detector spans hundreds of nanometres. Layer count and dispersion control matter more on polymer than on glass.
- Dichroic
- Wavelength-selective reflect-and-transmit stacks for fluorescence channels, IR cut filters, and combiner geometries. Designed for the angle-of-incidence range the assembly will see, not just nominal.
- Beamsplitter
- Plate and cube beamsplitters with engineered split ratios — non-polarizing or polarization-selective — designed against the polarization state the system actually presents at the splitter.
- Protected-metal mirror
- Aluminium and silver mirrors with dielectric overcoat for environmental durability. Uncoated polymer mirrors do not survive cleaning protocols; the overcoat is what makes them shippable.
Equipment
IAD coating chambers tuned for polymer thermal envelopes.
Coating chamber and process specifications.
| Capability | Specification |
|---|---|
| Chamber count | Two e-beam evaporation chambers with ion-assisted deposition (IAD) |
| Substrate temperature control | Chamber-wall control < 80 °C for PMMA, < 110 °C for PC; per-recipe envelope held against the polymer's heat-deflection limit |
| Fixturing | Substrate planetary fixturing for layer-thickness uniformity |
| Process monitoring | In-situ optical monitoring on every layer; quartz-crystal rate control |
| Spectral coverage | 380–2000 nm; UV (200–380 nm) available as a sub-scope |
| Material library | SiO₂, Ta₂O₅, TiO₂, MgF₂, Al₂O₃, Nb₂O₅ |
Polymer-specific challenges
The four failure modes that separate polymer coating from glass coating.
- Outgassing during pump-down
- Polymer absorbs water and residual processing gases; pump-down profile is staged to drive them out before the first layer lands. Skipping this step is what causes the inclusions you find at burn-in.
- Adhesion
- Plasma pre-treatment plus an adhesion-engineered first layer — chosen against the specific resin, not a single house recipe. Tape and severe-abrasion adhesion are verified per lot.
- Thermal budget
- The polymer caps the chamber temperature; the recipe has to land the same optical performance with less thermal latitude than glass. This is where most polymer coating programs slip.
- CTE mismatch
- Coating and substrate expand at different rates; thermal cycling drives microcrack initiation in stacks designed for glass. We tune layer stress and total thickness against the program's environmental envelope.
Reliability testing
Coatings are qualified in-house against the program's environmental envelope.
- Adhesion — tape and severe abrasion
- MIL-C-48497 references; methodology aligned to the customer's program.
- Humidity exposure
- MIL-STD-810 references; 85 °C / 85 % RH soaks on representative parts.
- Thermal cycle
- −40 °C to +120 °C cycling on the in-house environmental chambers; cycle count per program.
- Salt fog
- Salt-fog exposure where the application requires it (defense, marine, outdoor sensors).
The reliability evidence sits in the same release record as the per-part metrology — see the Metrology & Testing capability for the equipment that produces it.
Spectral profile
BBAR coating versus uncoated polymer across the visible band.
Send the substrate, the spectral target, and the environmental envelope.
We will tell you which stack family to start from, what the polymer side of the recipe needs to look like, and what reliability evidence we put on the release record.