1. A focusing unit, comprising: a core having multiple facets, wherein refractive indices of the core are responsive to an electric field applied on the core and the core is made of ultra violet durable material; a first set of electrodes coupled to a first facet of the core; a second set of electrodes coupled to a second facet of the core; wherein when the first and second set of electrodes induce an electrical field having a magnitude that has a substantially parabolic shape along a first direction, the core applies a first focusing function along the first direction on a first light beam that enters the core through an input facet of the core that differs from the first and second facets, the first direction being oriented along a propagation direction of the first light beam; and wherein fast changes in the electrical field result in fast changes in the first focusing function.
2. The focusing unit according to claim 1 , wherein the core is made of one of: Potassium Di-deuterium Phosphate, KH 2 PO 4 , Ammonium Dihydrogen Phosphate and Silicone DiOxide.
3. The focusing unit according to claim 1 , wherein a first one of the first and second sets of electrodes is arranged to induce an electrical field having a first magnitude that has a parabolic shape along the first direction and a second one of the first and second sets of electrodes is arranged to induce an electrical field having a second magnitude that has an inverted parabolic shape along the first direction.
4. The focusing unit according to claim 1 , wherein a first one of the first and second sets of electrodes is arranged to induce an electrical field having a first magnitude along the first direction that increases with a proximity to a center of the core, and a second one of the first and second sets of electrodes is arranged to induce an electrical field having a second magnitude along the first direction that decreases with the proximity to the center of the core.
5. The focusing unit according to claim 1 , wherein the first and second sets of electrodes are arranged to induce an electrical field that causes the core to act as a positive lens along the first direction and to act as a negative lens along the third direction.
6. The focusing unit according to claim 1 , wherein the first and second sets of electrodes are arranged to induce an electrical field that causes the core to act as a negative lens along the first direction and to act as a positive lens along the third direction.
7. A method for changing focus, comprising: receiving a first light beam through an input facet of a core made of ultraviolet durable material, wherein refractive indices of the core are responsive to an electric field applied on the core; inducing, by a first set of electrodes that is connected to a first facet of the core that differs from the input facet, an electrical field having a magnitude that has a substantially parabolic shape along a first direction thereby causing the core to apply a first focusing function along the first direction on the first light beam, wherein the first direction is oriented along a propagation direction of the first light beam; and performing a fast change in the electrical field induced by the first set of electrodes thereby performing fast changes in the first focusing function.
