Coating formation by reactive deposition

A coating apparatus comprising:

• a reactant inlet defining a reactant stream path wherein the opening of the reactant inlet is elongated in one dimension relative to the orthogonal dimension;
• a reactant supply system connected to the reactant inlet to supply a reactant along the reactant stream path wherein the reactant supply system comprises a reactant source;
• optical elements forming a light path intersecting the reactant stream path at a reaction zone with a product stream path continuing from the reaction zone wherein the light beam is oriented to project along the elongated dimension of the reactant inlet;
• and
• a first substrate intersecting the product stream path wherein the first substrate is positioned such that the substrate does not intersect with the light path;
• a motor connected to the apparatus such that operation of the motor moves the first substrate relative to the product stream;
• and
• a chamber sealed from the ambient atmosphere and a pump connected to the chamber, wherein the reactant inlet and the first substrate are within the chamber.