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Photothermal Common-Path Interferometry (PCI)
Precision Photonics (PPC) is now using in-house PCI for absorption measurements of substrate surfaces, coatings, and bulk materials at 1070nm. This new system is a key piece of metrology for applications with critical requirements for very low absorption coatings, such as the high power continuous wave (CW) lasers used in materials processing and directed energy. PPC is also utilizing these measurements to monitor the batch-to-batch quality of our ion-beam-sputtered (IBS) optics and coatings.
Photothermal Common-Path Interferometry (PCI) is a metrology method that creates and measures a tiny, localized thermal lens with sensitivity of less than 1 part-per-million (ppm) for fractional absorption. It uses a strong pump beam to create the thermal lens effect in conjunction with a weak probe beam to detect the resulting aberration. The technique is insensitive to scatter, non-destructive, and can measure bare or coated surfaces as well as bulk material absorption of a substrate.
Actual coating absorption < 1 ppm!
(Measured at 1070 nm using PPC's new PCI system)
- Total absorption at coated surface is ~1.5 ppm
- Bulk absorption corresponds to ~0.8 ppm
- Uncoated surface absorption is ~1.0 ppm
- Actual AR coating absorption is < 1 ppm
Custom low absorption AR coatings now available for high power lenses |
