Methods and apparatuses for fabricating polymeric conformal coatings, parts coated with polymeric conformal coatings, and optical apparatus including said parts

A method of forming a Fabry Perot interferometer, the method comprising:

• depositing a first reflective layer (104b) on a part (23), thereby defining a first reflective surface of the part;
• vapour depositing polymeric conformal coating on the first reflective surface of the part, the vapor depositing comprising:
• placing the part and a flow control screen in a deposition chamber;
• dispersing a gas into the chamber from which the polymeric coating is deposited on the surface;
• wherein the flow control screen is spaced apart from the first reflective surface and is configured to control a localised flow of the dispersed gas in the chamber so as to impose a structure, in the form of a thickness variation, on the deposited coating, wherein the flow control screen comprises openings such that imposing a structure on the deposited coating produces an array of curved elements, wherein the curved elements extend beyond the region defined by the perimeter of the openings of the flow control screen;
• and
• depositing a second reflective layer on the polymeric coating to define a second reflective surface in opposition to the first reflective surface, to thereby form the Fabry Perot interferometer with the polymeric coating (106) as the optical cavity of the Fabry Perot interferometer.