Guided wave structure

In addition to studies of diacetylene single crystals, current research, activities are focused on studies of the second X and third x order nonlinear optical responses of disubstituted diacetylene polymer films as active optical guided wave structures. Diacetylene polymers possess X values comparable to germanium(j 7). In the first stage, three major questions are being addressed ... 

Let us consider a multilayer structure plotted schematically in Fig. 1. It will be taken as a fundamental building block of any more complex guided-wave structure considered here. Let the optical wave propagate along the longitudinal coordinate z, and x is the transversal coordinate. 

Chu, S.T. and Chaudhuri, S.K., 1989, A finite-difference time domain method for the design and analysis of guided-wave optical structures, J. Lightwave Technol. 7 2033-2038. 

Two of the advantages of using such materials are flexibility in the fabrication of optical structures and the tailoring of optical properties through material engineering. For application in guided-wave nonlinear optical devices high optical quality and low dielectric constant are but two of the requisite properties. 

Fig. 3 Schematic of the guided wave resonant structure to elucidate the origin of the resonance in reflection...

Tervonen A., Poyhonen P., Honkanen S., Tahkokorpi M., A guided-wave Mach-Zehnder interferometer structure for wavelength multiplexing, IEEE Photonics Technol. Lett. 3... 

An important concern is two-photon absorption which can also become a significant problem at high power densities, especially in the guided wave geometry. These excitations are even more of a problem in multiple quantum well devices and quantum confined structures because direct two-photon absorption can create free carriers which decay very slowly, giving rise to a slow nonlinear response. Molecular and polymeric materials offer additional flexibility to shift the two-photon resonances by chemical modifications. 

Figure 16.7 Use of piezoelectric wafer active sensors (PWAS) for damage detection with ]MDpagating and standing guided waves in thin-waU structures, (a) pitch-catch (b) pulse-echo (c) thickness mode (d) impact and acoustic emission (AE) detection (e) electromechanical (E/M) impedance (f) PWAS phased array.

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