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The inductively coupled plasma etching parameters for fabricating sensing windows of integrated Mach-Zehnder interferometer sensor based on polymers are systematically investigated. Under the optimum etching condition, we fabricate an improved sensing waveguide with three sensing surfaces, whose sensitivity can be enhanced by a factor of 3.5 in theory. Through precisely controlling the etching time, low propagation loss and high hydrophilicity are both achieved in the etched sensing waveguide. This optimizing approach along with rapid response and stable operation has rendered the MZ1 wave-guide sensor more competent to practical requirements of R1 sensing and biochemical sensing. [ABSTRACT FROM AUTHOR]

A polymer mode multiplexer based on asymmetric couplers is theoretically designed and experimentally demonstrated. The proposed X-junction coupler is formed by waveguides overlapped with different crossing angles in the vertical direction. A beam propagation method is adopted to optimize the dimensional parameters of the mode multiplexer to convert LP01 mode of two lower waveguides to LP11a and LP21a mode of the upper waveguide. The ultraviolet lithography and wet chemical etching are used in the fabrication process. A conversion ratio over 98% for both LP11a and LP21a mode in the wavelength range from 1530 to 1570 nm are experimentally demonstrated. This mode multiplexer has potential in broadband mode-division multiplexing transmission systems. [ABSTRACT FROM AUTHOR]

An optical waveguide displacement sensor according to core-cladding modes interference is theoretically proposed and experimentally demonstrated. Ultraviolet sensitive SU-8 polymer on silica is used as the guiding layer. It is covered by a 12 nm thick planar gold grating. The air gap sensing head which consists of the waveguide end and the single-mode fiber facet can realize the displacement detection by monitoring the wavelength dip shifting in transmission spectra. Cladding modes propagating in the exposed SU-8 can be effectively excited by the end-fire coupling because of the mode field mismatch between the SU-8 waveguide and lead-in fiber. A sinusoidal pattern transmission spectrum in C-band with the depth of over 14 dB can be observed due to the interference between the core and cladding modes. Peaks in the transmission spectrum vary continuously with the position offset of input fiber facet from the center of waveguide end. Both the sensitivity and the stability of sensing are enhanced by the introduction of nanometric gold gratings. The fabricated displacement sensor exhibits a high sensitivity of 2.3 nm μm−1, promising potentials for micromechanical processing and integrated optics application. [ABSTRACT FROM AUTHOR]