Optical travelling-wave

Figure 6.11. Traveling wave single-mode LiNbOj electro-optic modulator.

I he notation 0e indicates that this is the dielectric function at frequencies low i ompared with electronic excitation frequencies. We have also replaced co0 with l (, the frequency of the transverse optical mode in an ionic crystal microscopic theory shows that only this type of traveling wave will be readily excited bv a photon. Note that co2 in (9.20) corresponds to 01 e2/me0 for the lattice vibrations (ionic oscillators) rather than for the electrons. The mass of an electron is some thousands of times less than that of an ion thus, the plasma liequency for lattice vibrations is correspondingly reduced compared with that lor electrons. 

The simple analysis presented above confirms that new formulations are required to produce stable, reliable products for field use. Practical system requirements, as defined by Mil Spec conformity and the use of standard fabrication and assembly processes, definitely require that a electro-optic polymer system with better thermal properties than thermoplastic acrylates be developed. That this is true for optical interconnection boards and modules is not surprising because of their complexity. It is perhaps remarkable that it remains true for even simple devices, such as a packaged, pigtailed traveling-wave modulator. The ultimate success of electro-optic polymers will be their use in cost-effective products that are used by systems designers. 

Figure 4.9 Schematic of bulk electro-optic phase modulator in transverse geometry (a) standard electrode arrangement for static measurements, (b) travelling wave configuration...

In last years one observes a fast progress in synthesis and elaboration of non-centrosymmetric functionalized polymers for applications primarily in electrooptic modulation and frequency conversion. These materials possess large second order nonlinear optical susceptibility x and can be easily processed into good optical quality thin films for travelling wave applications. Essentially four types of polymeric structures have been developed, as shown in Fig. 1 ... 

C.J. Borde, C. Salomon, S.A. AvriUier, A. Van Lerbeighe, C. Breant, D. Bassi, G. Scoles, Optical Ramsey fringes with travelling waves. Phys. Rev. A 30,1836 (1984)... 

Zhao, Y.G., A. Wu, H.L. Lu, S. Chang, W.K. Lu, S.T. Ho, M. Van der Boom, and T.J. Marks. 2001. Traveling wave electro-optic phase modulators based on intrinsically polar self-assembled chro-mophoric superlattices. Appl Phys Lett 79 587-589. 

The onset of stimulated emission can be detected by a collapse of the broad emission spectrum to a narrow line. This line narrowing due to optical gain in a waveguide without resonator is commonly referred to as amplified spontaneous emission (ASE) [49], or travelling wave lasing, hi the case of additional optical resonators like gratings or microcavities, different modes with much narrower linewidths can be resolved. 

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