We have investigated the in-plane switching of cholesteric liquid crystals for reflective wavelength shifters for visible and near-infrared applications. These devices are based on the elongation of the cholesteric pitch by an electric field perpendicular to the helical axis. The transmission notch-reflection peak position can be tuned continuously to a longer wavelength (redshift) by application of an in-plane electric field. The helix is completely unwound when the electric field is higher than the cholesteric-to-nematic transition field, and the sample is transformed to a transparent state. We have investigated the electro-optic performance of in-plane switching of cholesteric samples and developed a simple phenomenological model to describe the underlying electro-optic phenomena.