Christopher Cook, Becca Silver, Tyler Cristy, Edmund Optics, Barrington, NJ
Metrology capable of measuring differential phase-error (dp-ds) or intentional phase-shift of coated surfaces are not commonplace in the coating factory or even the laboratory in many cases. Polarimeters using Meuller-matrix or Stokes-vector analysis are available that can be used to determine polarization ellipticity from which phase-error can be derived; however, these systems cannot easily measure accumulated phase-lag in more complex (multibounce) optics such as prisms. Spectrophotometers are more commonplace to both the laboratory and factory, and some can be adapted with the use of attachments (i.e. optical-bench) enabling setup and measurement of phase for more complex samples and applications. However, such approaches require manual set-ups which are inherently less repeatable/versatile alignment-insensitive, lower efficiency integrating-sphere type detectors and enclosure schemes that can lead to elevated levels of stray-light. Lower accuracy due to higher noise and stray-light are inherent disadvantages to these options.
As the demand for high precision optical components increases, so does the demand for a full metrology suite that provides verifiably accurate data required to meet demanding specifications. We present on a phase metrology method that integrates commercially available motion-control driven components with the built-in automation of a commercial RT spectrophotometer. The resulting system is versatile enough to allow multiple configurations for both measurement and validation along with both high-efficiency detection (low-noise) and low stray-light. We demonstrate accuracy via multiple unique validation approaches and subsequently generate low-noise accurate phase-measurements for use in the development, optimization and reverse-engineering of reflective waveplate coatings, specifically 8^th wave metal-dielectric and LIDT rated all-dielectric components. This approach integrates a relatively low-cost upgrade to existing automated instrumentation to produce a reliable and robust phase-metrology capability essential to the operation of highly functional coating factories.