High rate deposition for the formation of high quality optical coatings

A method for forming an optical coating on a planar substrate in a chamber, the method comprising depositing a powder coating on the planar substrate from a product flow:

• wherein the product flow results from a chemical reaction in a reactant flow comprising a first precursor,
• wherein the chemical reaction is driven by a light beam,
• wherein the planar substrate has a surface area of at least about 25 square centimeters,
• wherein a nozzle that directs a source of the reactant flow along a propagation direction into the chamber is moved within to the chamber to thereby move the reactant flow relative to the substrate and the chemical reaction is driven by a light beam that is moved within the chamber relative to the substrate,
• wherein the reactant flow has a cross section perpendicular to the propagation direction characterized by a major axis and a minor axis, the major axis being at least a factor of two greater than the minor axis, and the major axis is sufficiently large that the product flow simultaneously forms a layer on the substrate along an entire linear dimension extending across the substrate resulting in the deposition of the layer on the substrate with one linear pass of the product flow across the substrate,
• wherein the nozzle is connected to a flexible conduit that provides the reactants, with the flexible conduit moving inside the chamber as needed to provide a continuous supply of the reactants as the nozzle moves,
• wherein moving the light beam comprises
• passing the light beam into the chamber through a first window, directing the light beam through the reactant flow in a direction parallel to the major axis, and passing the light beam out of the chamber through a second window, with the directing of the beam comprising reflection with a plurality of mirrors, and
• moving the beam with the reactant flow to maintain passage of the beam through the reactant flow and parallel to the major axis,
• wherein the method comprises depositing a powder coating comprising the layer on the planar substrate from a product flow with the powder coating having a thickness of at least about 100 nm in no more than about 30 minutes, and
• wherein the powder coating consolidates under appropriate conditions into an optical coating having a standard deviation in index-of-refraction across the planar substrate of less than about 0.001 with a 1 centimeter edge exclusion.