| Popis: |
Polymer multilayer structures have attracted increasing attention in the recent years because of the straightforward and low-cost techniques that can be used for their fabrication. When the multilayers are composed of a periodical alternation of two materials with different refractive indexes and with layer thicknesses comparable with the wavelength of light, they take the name of distributed Bragg reflectors (DBR). They behave like planar one-dimensional photonic crystals (PhC) and exhibit a photonic band gap (PBG), a spectral region in which photons with suitable energy and wave vector are not allowed to propagate through the crystal. Moreover, within the PBG and at its edges, modifications of radiative photophysical processes occur. The spectral position, efficiency and linewidth of the PBG can be engineered by modifying the layer thicknesses and the refractive indexes of the two materials. While DBRs grown using inorganic materials are well known, polymer and colloidal particle DBRs are receiving a renewed interest due to the possibility to chemically engineer their structural properties and photonic functions; moreover, they can be free-standing and flexible thus being adaptable to any surface. Furthermore, polymers and porous structures can easily embed many other active materials, paving the way to a myriad of applications. In this chapter, we introduce polymer multilayers and planar microcavities fabricated using the spin coating technique, discussing the different materials employed and manufacturing challenges. We will also review different applications that exploit these kinds of photonic structures ranging from lasing to sensing. |
