Polymer planar waveguides

Planar, i.e. rectangular, waveguide components are applied in many photonic devices. They can be easily manufactured at low cost. Typical applications relate to computer backplanes combining electrical and optical cables [87], thermo-optical svdtches [88], optical splitters of multichannel high-density planar lightwave circuits [89], and polyimide-based electro-optical (EO) modulators [90]. 

---

Figure 10-11. The sample is a 290 nm thin film of LPPP deposited on a BK7 substrate. A planar waveguide glass/polymer/air is formed since the polymer film has the highest index of refraction. The resulting intensity profile of the guided TE waveguide mode for the sample is shown on the right hand side. Only one guided mode is supported.

Figure 10-15 shows the output vs. input energy relation with a clear threshold at a pump pulse energy of approximately 1.5 nJ. This value is an order of magnitude lower than the threshold for the observation of ASE in simple planar waveguides, i.e. without distributed feedback but prepared with the same conjugated polymer. 

There are two major types of planar waveguides - those with a graded index and those that are step-indexed, as shown in Fig. 4. Waveguides can be composed of any optically transparent material such as glassy materials and polymers, depending on their structure. 

We note also that PM SHG was obtained with poled polymer thin films using a planar waveguide with corrugated grating [ 187]. 

The sensitivity enhancement due to lasing action is a general principle that is independent of sensor architecture. Chemical sensitivity enhancements have been observed when the polymer is fabricated into a simple planar waveguide (Fig. 5.11a), deposited over a distributed feedback (DFB) grating (Fig. 5.11b) and coated on the exterior of an optical fiber (Fig. 5.11c). 

Chang, D.H., T. Azfar, S.K. Kim, H.R. Fetterman, C. Zhang, and W.H. Steier. 2003. Vertical adiabatic transition between silica planar waveguide and electro-optic polymer fabricated using grayscale lithography. Opt Lett 28 869-871. 

Ne laser via a grating into a planar waveguide to measure changes in the refractive index at the solid-liquid interface.This technique enables the direct, on-line monitoring of the adsorption of macromolecules such as proteins, lipids, or polymers. 

FIGURE 3 Ordinary (nj and extraordinary (n ) refractive indices of DANS side-chain polymer poled at 80 V / /xm (nominal poling field). The data were obtained by m-line spectroscopy with a grating coupler on a planar waveguide. 

---