Electro-polymerization

In addition to the chain reaction, like vinyl polymerizations, electro-lytically step-by-step reactions are also rationally to be applied to polymer synthesis. However, electrochemical reaction is not favorable for such a step-by-step reaction, since a growing polymer chain end must be affected at the electrode at each step of the reaction. Hence, only few peculiar attempts have been found successful. 

Fig. 6. Measurement of photostability of two polymeric electro-optic materials as carried out by researchers at IPITEK (TACAN) Corporation. The data represented by the solid line correspond to the LRD-3 DEC material of Dalton and co-workers [138] while the data represented by open circles correspond to a diaminonitrostilbene chromophore/poly(methyl methacrylate) guest/host material produced by IBM Almaden Laboratories. The dramatic improvement observed for the DEC material can be associated with increased lattice hardness from the chromophore coupling to adjacent polymer chains...

Fig. 21. Dynamic thermal stability [121] of a variety of polymeric electro-optic materials. All materials involve the Disperse Red chromophore. Trace 1 PMMA composite material trace 2 chromophore covalently attached by one end to a soft (PMMA-like) matrix [138] trace 3 DEC chromophore with both ends attached to a soft polymer matrix [138] trace 4 Disperse Red chromophore covalently attached at one end to a polyimide polymer matrix [121] trace 5 DEC-type chromophore with both ends attached to a sol-gel type matrix [139]...

As already noted, resistive loss in metal electrode structures and in transition from millimeter wave waveguides to the electrode structure is the greatest problem in achieving 100 GHz and higher electro-optic modulation. Fetterman and co-workers [301] have shown by pulse techniques that the 3-dB bandwidth of polymeric electro-optic materials is typically in the order of 360 GHz for 1 cm of material. Stripline electrode structures have been used to achieve operation to somewhat above 100 GHz. Fetterman and co-workers [282] have recently described a novel finline transition between a millimeter waveguide and such elec-... 

Measurement of device bandwidths in the order of 100 GHz typically requires heterodyne detection and a stripline electrode configuration such as that illustrated in Fig. 31. The response of polymeric electro-optic modulators is typically flat to 100 GHz. Fall off above that frequency (Fig. 32) can be traced to resistive losses in millimeter wave transmission structures and in the metal electrodes. 

Optical propagation loss for polymeric electro-optic materials is typically in the order of 1 dB/cm when care is taken to avoid scattering losses associated with processing and poling-induced damage [2, 3, 5, 63, 64, 257]. Lower loss values can be obtained by isotopic replacement of protons with deuterium and with halogens [211, 304, 305]. With effort, electro-optic material losses can be reduced to approximately 0.2 dB/cm for the telecommunication wavelengths of 1.3 and 1.55 microns. 

TACAN has prepared a summary table of the performance of polymeric electro-optic materials and comparison with inorganic materials (Table 5). Note that, although this compilation by TACAN is only a year old, the future performance of polymeric electro-optic materials has already been realized. 

Fig. 34. DC bias voltage stability (measured by the TACAN Corporation) of a polymeric electro-optic modulator operating at 1550 nm...

At the present time, no significant commercialization of polymeric electro-optic modulators exists. However, that situation appears be changing rapidly. Pacific Wave Industries now offer a variety of broad bandwidth modulators for purchase and firms such as Radiant Research, IPITEK and Lumera Corporations are dramatically expanding their activities. Figure 35 shows the PWI40 GHz modulator fabricated from CLD-l/APC polymer material. 

Nontraditional methods of polymerization (low temperature radical polymerization initiated by organometallic compounds, ionic and ion-coordination polymerization, electro- and photochemical initiation, etc.) with nontraditional monomers (which are undoubtedly MCMs) will in future receive much more attention. At present, intensive research into solid-phase polymerization is ongoing. The reason is to avoid the problems that appear during MCM polymerization, namely, those connected with the selection of an appropriate solvent and initiator, with precipitation of the polymeric product and with removal of residual reaction-medium components from the product. 

POLYMERIC ELECTRO-OPnC MATERIALS AND DEVICES MEETING THE CHALLENGES OF PRACTICAL APPLICATIONS... 

Dalton, L.R., A.W. Harper, A. Ren, E Wang, G. Todorova, J. Chen, C. Zhang, and M. Lee. 1999. Polymeric electro-optic modulators From chromophore design to integration with semiconductor VLSI electronics and silica fiber optics. Ind Eng Chem Res 38 8—33. 

Dalton, L.R., A.W. Harper, B. Wu, R. Ghosn, J. Laquindanum, Z. Liang, A. Hubbel, and C. Xu. 1995. Polymeric electro-optic modulators Materials synthesis and processing. Adv Mater 7 519-540. 

Zhang, C., H. Zhang, M.C. Oh, L.R. Dalton, and W.H. Steier. 2003. What the ultimate polymeric electro-optic materials will be Guest-host, crosslinked, or Side-chain. Proc SPIE, 4991 537-551. 

Pereverev, Y.V., O.V. Prezhdo, and L.R. Dalton. Mean field theory of acentric order of dipolar chromophores in polymeric electro-optic materials. Chromophores with displaced dipoles. Chem Phys Lett 340 328-335. 

Thackara, J. I., Bjorklund, G. C., Fleming, W., Jurich, M., Smith, B, A., and Swalen, J, D., A polymeric electro-optic phase modulator for broadband data transmission, in Nonlinear Optical Properties of Organic Materials VI (G. F. Mohlmann, ed.), Proc. SPIE, Vol. 2025, 1993, pp. 564-573. 

Polymeric electro-optic materials also attracted attention because of potential for dramatically improved length-bandwidth product and putative improved pro-cessibility, which could translate into improved integration with very large scale integration (VLSI) semiconductor circuitry. Unlike the situation with LiNb03, optical loss is a potential problem for organic materials that must be carefully considered for each device application. 

II. THE MULTISTEP FABRICATION OF POLYMERIC ELECTRO-OPTIC MODULATORS SYSTEMATICALLY CREATING STABLE ORDER FROM CHAOS... 

FIGURE 23 Fabrication of a buried channel polymeric electro-q[>tic modulator by reactive ion etching (RIE). 

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