Light passing through a photonic crystal can undergo a negative or a positive refraction. The two refraction states can be functions of the contrast index, the incident angle and the slab thickness. By suitably using these properties it is possible to realize very simple and very efficient optical components to route the light. As example we present two devices: a passive device acting as a polarizing beam splitter and a tunable switch. In the first device TM polarization is refracted in positive direction whereas TE component is negatively refracted, in the second device the light is positively refracted at room temperature and negatively refracted varying the local temperature of the device.