I want to design some wave guide that I changed the refractive index in case of Ion-Exchange in the channel, now I want to have gold on top of one arm in case of sensing and on the gold I want to put for example sliver so far I tried to change the cladding but it will change for whole design, is there any option to change the cladding for just one area? or can we have so many cladding on top of the design?