Search

We propose electric poling of electro-optic (EO) polymer films with graphene electrodes. The use of graphene electrodes can waive the use of buffer layers and minimize the poling voltage. To demonstrate the idea, we prepared EO polymer thin-film waveguides for poling with traditional Au/ITO electrodes and graphene electrodes, where the EO polymer is a guest-host system formed by doping 15 wt% of dipolar polyene chromophore AJLZ53 into the random copolymer P(S-co-MMA). Our experiments confirm that the use of graphene electrodes can significantly reduce the poling voltage. For a 3.8-µm-thick EO polymer film, we achieve high EO coefficients of 82 pm/V at 1541 nm and 110 pm/V at 1300 nm with a poling voltage of 420 V. In addition, the use of graphene electrodes allows more flexible waveguide designs and can potentially simplify the fabrication of devices based on EO polymer.

We propose a novel optical fiber design that consists of a uniform core and a segmented cladding formed by alternate regions of high and low refractive indices in the azimuthal direction. The structure is analyzed by use of the radial effective-index method, and the propagation characteristics of the structure are studied. The fiber has a highly dispersive cladding and shows characteristics similar to those of photonic-crystal fibers and holey fibers. The novel fiber offers the possibility of single-mode operation over a wide range of wavelengths with a large core diameter.

We show that recent experimental results of Wong et al. [Opt. Lett. 17, 1773 (1992)] on the effect of UV photolytic processing on the birefringence of elliptical-core fibers arise from a 15-30% reduction of the coefficient of thermal expansion of the germanosilicate core. An explanation based on reconfiguration of the glass network to minimize the stress energy during UV processing is proposed.

An asymptotic study of the effective-index method for the analysis of rectangular-core dielectric waveguides is given. Two ways of applying the effective-index method, depending on how the effective index is calculated, are considered, and expressions for the errors in the calculation of the propagation constant are derived. These expressions show explicitly how the accuracy of the method varies with the normalized frequency, the mode orders, the dimensions of the waveguide, and the relative refractive indices of the core and the surrounding media. Many novel properties of the method are revealed by these expressions. For example, it can be shown that the effective-index method can underestimate the propagation constant for a strip waveguide.

Fused tapered single-mode fiber couplers are analyzed in detail by the simple effective-index method. It is found that the core parameters of the coupler, i.e., the core-cladding radius ratio, the core-cladding profile height, and the core separation, can have significant effects on the coupler characteristics. In practice, neglect of the cores as in many previous studies may lead to intolerable errors.

A sensor consisting of two fiber-optic interferometers of slightly different sensitivities can offer both high sensitivity and a wide dynamic range when the phase difference between the two interferometer outputs is used to identify the order of the fringe from either interferometer output. This technique is demonstrated with a polarimetric temperature sensor utilizing two different lengths of stress-induced birefringent fibers as sensing elements.

A simple, accurate, and nondestructive method based on acousto-optical modulation of the polarization and the optical frequency in a linearly birefringent fiber is proposed for measuring the beat length of the fiber. Short beat lengths can be measured by this method with an accuracy of the order of 1%. This method can also be used to identify the local polarization axes of the fiber.