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The actual method chosen depends firstly on what (geometry) it is that you
wish to coat. Secondly, the method chosen to coat (PMMA) is dependant upon
the coating thickness required and the homogeneity of the coating required.
Generally spin coating is the (my) preferred technique, and results in the
highest quality coatings, as well as the thinnest. Spin coating involves
loading the substrate to be coated with a solution of the polymer (PMMA) in
a suitable solvent (cyclohexanone, o-xylene, benzene). The solution
concentration used depends upon several parameters, including the thickness
and quality required from the final coating. Typical concentrations of
polymer solutions for fabricating waveguide devices (~1 micron thick) would
be ~ 100 g/L. Once loaded onto the substrate, the substrate is rotated at
high speed w (0