Propagation Loss And Application Research In Symmetrical Metal-Cladding Optical Waveguide With Sub-Millimeter Scale

Symmetrical metal-cladding optical waveguide (SMCOW) is one of the most important components in the field of optical communication and integrated opt-electronics. Based on SMCOW structure,a variety of opt-electronic devices have been used more and more, especially in sensor applications. However, in the visible and near infra-red spectra, according to the characteristic of dielectric constants of the noble metals, it is generally believed that light energy will be absorbed strongly during transmission, the high propagation loss is resulted. Therefore, the transmission distance can not achieve at millimeter-scale in the SMCOW and the scope of its application is greatly restricted by the high propagation loss, which can not make the idea of mini-pulse broadening devices come true. To overcome the shortcoming of the high propagation loss in SMCOW, a new method, which the use of the guiding layer with sub-millimeter can effectively inhibit the propagation loss, has been proposed.In this paper, according to the dispersion equation of SMCOW and the characteristic of dielectric constants of the noble metals (gold or silver), the real part is minus and its absolute value is much larger than that of the image part. A first-order perturbation is used to study the loss properties in such waveguide. By this mean, the analytic formulas of perturbed propagation constants of TE and TM modes are obtained.It is shown that the propagation loss is inversely proportional to the thickness in SMCOW. While the guided wave layer thickness with sub-mm scale, the propagation loss is about three orders of magnitude lower than in micron-scale. It is entirely possible that the transmission distance of millimeter scale can be obtained in SMCOW with sub-mm. The result of first-order perturbation is in good agreement with the numerical calculation based on the strict dispersion equation. Both of them show that the use of the guiding layer with sub-mm can inhibit the propagation loss effectively.The theoretical calculations also show using gold, silver as cladding-materials in SMCOW with sub-mm, the propagation loss is generally less than3d B /mm ,and the light intensity attenuation factor is small, optical signal can still keep well after transmission mm distance. Based on this theory, mini-pulse broadening devices can be developed possibly.In order to substitute for chirped-pulse-amplification (CPA) technology in a large broadening of the grating, according to the strong dispersion of the ultrahigh-modes in SMCOW with sub-mm–scale, the idea of the miniaturization device is proposed, which make pulse width achieve to 1000 times in the transmission distance mm magnitude.