A diffractive optical element is fabricated in soda-lime float glass using a simple and inexpensive process. The glass is sandwiched between a mesh anode (lattice constant 2 μm) and a flat metal cathode. Applying a direct current while at a moderately elevated temperature of 553 K induces thermal poling of the glass. The result is that the structured pattern of the electrode is imprinted on the glass as the electric field causes ion depleted regions...