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Polarization Dependence of Phase-Only Spatial Light Modulators (SLM) | Thorlabs Insights Topic Focus

The optical working principles of liquid crystal on silicon spatial light modulators (SLMs) that are designed to provide phase-modulated output beams are illustrated in this video. The input beam must be linearly polarized and oriented parallel to a direction that is often described as the SLM’s optic axis. This input polarization orientation is necessary to maintain the polarization state of the light and provide an output beam with the expected characteristics. The polarization state of the input beam affects the output beam’s optical properties, since the liquid crystal layer is birefringent. The birefringence is due to the liquid crystal being composed of a multitude of ellipsoidal and spatially ordered molecules. Light polarized parallel to the long axes of the molecules experiences a higher refractive index than light polarized parallel to the short axes. These molecules rotate in response to a voltage applied across the liquid crystal layer. The optic axis of the liquid crystal is in the rotation plane of the molecules. The SLM tunes the refractive index, and therefore the optical path length, of individual pixels by modulating the voltage applied across each pixel. The effect of the molecules’ rotation on the refractive index of the liquid crystal layer is shown using animations and a few equations. Click on this link (   • Calibrate a Spatial Light Modulator (...  ) to watch the Video Insight that was the inspiration for this Topic Focus video! 00:00 Key Component Overview 00:52 Voltage Controls Refractive Index 01:14 Phase Delay & Optical Path Length 01:34 Molecules & Birefringence 02:49 Parallel to Rotation Plane 04:12 Perpendicular to Rotation Plane For more photonics how-to videos, visit https://www.thorlabs.com/newgrouppage...