Waveplate Retardance Metrology: The Basics and Beyond

INTRODUCTION
Waveplates are important for the control of the state of polarization and for the measurement of polarization of light. They are modifiers of polarization state but not of the degree of polarization. They do this in a manner described by a parameter called retardance. Most commonly the needed retardances are either half wave or quarter wave. The accuracy to which these retardances are met by the waveplate determines the purity of the desired polarization state produced on output. Unfortunately, waveplate manufacturers and waveplate users often do not have an easy and accurate way to measure this important retardance parameter. We discuss here the basics and limits of retardance metrology as well our capabilities and equipment here at Meadowlark Optics for this retardance metrology.