Light reactive deposition uses an intense light beam (684) to form particles that are directly coated onto a substrate (680) surface. In some embodiments, a coating apparatus comprising a noncircular reactant inlet (682), optical elements forming a light path (684), a first substrate (680), and a motor connected to the apparatus. The reactant inlet (682) defines a reaction zone with a product stream path continuing from the reaction zone. The substrate (680) intersects the product stream path. Also, operation of the motor moves the first substrate (680) relative to the product stream. Various broad methods are described for using light driven chemical reactions to produce efficiently highly uniform coatings.