Optical filter alternate films

Figure 15.24 shows the fabrication process of the optical filter on a fluorinated polyimide substrate. First, the low-thermal-expansion-coefficient PMDA/TFDB poly(amic acid) solution was spin-coated onto a Si substrate and baked. Then alternate TiO2 and SiO2 layers were formed on the polyimide film by ion-assisted deposition. The multilayered polyimide film was diced and peeled off from the Si substrate. In this way, thin optical filters on a fluorinated polyimide substrate are easily fabricated. 

The general approach used to make a dielectric mirror is to lay down a stack of thin films that have alternately higher and lower refractive indices. Manipulation of the thickness and the refractive index of each layer in the stack allows the optical properties to be modified at will to produce virtually perfect mirrors and virtually perfect antireflection coatings - both of which can be mned to respond to very specific wavelengths - as well as a variety of optical filters. The fabrication of such devices falls... 

Outside of alluding to the importance of PLCs in the fabrication of ultra-high strength organic materials, I have not addressed the applications of PLCs, a major source of the intensive interest in PLCs. The slower time scales for mesophase reorientation will limit the use of PLCs in dynamic electro-optical devices, but the possibility of locking in liquid crystal textures into stable solid polymer films renders PLCs attractive alternatives in static optical devices, e.g., as polarizers, notch filters and non centro-symmetric matrices for non-linear optical phenomena. 

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