The possibility of constructing light modulators and deflectors based on polariton effects is considered. The polariton is a mixed complex consisting of a superposition of a one-photon state and a crystal excitation state. By influencing the crystal excitation state by means of external fields, the polariton, and hence the photon part, can be deflected or modulated. The connection with geometrical optics is established, and it is shown that the deflection is due to a gradient in the refraction index created by the applied external field. Several examples with electric, magnetic, and stress fields, and temperature gradients are shown with orders of magnitude of deflections computed. Journal of Applied Physics is copyrighted by The American Institute of Physics.