Meadowlark Optics, Inc. MWIR Variable Retarder LPR-300-λ

Liquid crystal technology for polarization control now extends into the mid IR. Meadowlark’s standard line of polarization controllers can be used for these new variable retarders. They can be custom configured for use as variable attenuators and as polarization rotators.

Our Liquid Crystal Polarization Rotator (LPR) continuously rotates the polarization orientation of a monochromatic, linearly polarized input beam. Our LPR consists of a compensated Liquid Crystal Variable Retarder combined with a zero-order polymer quarter-wave retarder. The fast axis of the liquid crystal variable retarder is oriented at 45° to the slow axis of the quarter-wave retarder and the linearly polarized input must be parallel to the quarter-wave retarder slow axis. Polarization rotation is achieved by electrically controlling the retardance of the Liquid Crystal Variable Retarder, eliminating any mechanical motion.

A quarter-wave retarder converts elliptical polarization formed by the Liquid Crystal Variable Retarder to linear polarization. The rotation angle is equal to one-half the retardance change from the Liquid Crystal Variable Retarder.

Response time of the LPR depends upon the desired amount of rotation. Small rotations have a longer response time because of a smaller change in the electric field strength.

Polarization purity is defined as the ratio of the rotated linear component to the orthogonal component and, on average, polarization purity (or extinction ratio) is better than 150:1.

We provide test data including the required voltages corresponding to polarization orientations, in 10° increments, from approximately -40° to approximately 140° rotation. These measurements are taken at ambient temperature for your specified wavelength.

Standard Liquid Crystal Polarization Rotators are supplied without an input polarizer. Input polarization direction must be precisely aligned for optimum performance.