Dual Frequency Nematic Liquid Crystal Devices for Fast Optical Filtering*

Fast switching optical filters are of vast interest for multiple applications in various fields, from biomedical imaging and microscopy to light detection and ranging (LIDAR) systems. Modern applications require multispectral narrowband tunable devices with fast switching speeds. We present dual frequency nematic liquid crystal tunable filters based on a series of liquid crystal optical retarders, each placed between crossed polarizers. By choosing the liquid crystal retarders thicknesses and using individual biasing schemes, we continuously tune the wavelength and bandwidth of the filter with fine-tuned switching speeds in the ms regime. The filter was added to conventional polarized total internal reflection fluorescent (p-TIRF) microscopy to control which spectral wavelengths from fluorescent samples reach the detector. Our filter switching speeds allow imaging of different cellular processes on a ms time scale, which is an order of magnitude faster than typical mechanical filter switching speeds, resulting in improved temporal resolution. The results of electro-optical filter characterization and an example of its application in p-TIRF microscopy will be presented.