Liquid crystal phase retarder with broad spectral range

摘要: Abstract Phase retarders normally show a strong wavelength dependence of retardance. For example even without taking birefringence dispersion into account quarterwave retarder designed for 600 nm acts as halfwave at 300 nm. Achromatic phase with retardance changes only ±5% in ≈200 broad spectral regions can be assembled from two layers different birefringent materials the fast axes which are crossed. Further improvement is possible by combining three achromatic based on recipe given Pancharatnam. A plate realized an inner axis positioned certain angle respect to outer retarders. With this design kept constant within ±2% entire visible spectrum 400 900 We report first realization such band using liquid crystals instead materials. Although performance not good calculated it well comparable practically crystalline `superachromatic'