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A miniature fiber sensor tip with both high refractive index (RI) and temperature sensitivities was proposed for measuring the temperature and liquid RI simultaneously. A two-photon polymerization technique was used to fabricate a ⊓-shaped polymer micro-structure on the end-face of an optical fiber. A three-wave Fabry–Pérot interferometer was formed. The size of the proposed FPI can be precisely controlled and the total height is less than 30 μm. Temperature and RI variations can be detected simultaneously using the sensitivity matrix method. The sensor tip can be used in harsh environments, as cross-linking SU-8 has moderate acid and alkali resistance and good mechanical strength.

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We report on the formation of polarization dependent ripples on ZF(6) glass by femtosecond laser irradiation. Two kinds of polarization dependent ripples are formed on the laser modified region. The ripples with direction parallel to laser polarization distribute in a pit in the center of laser modified region, the period of the ripples increases with the increasing pulse number. The ripples with direction perpendicular to laser polarization spread around the pit, the period of the ripples (~750 nm) almost keeps constant with the increasing pulse number.

For what is to our knowledge the first time, the thermal-stress formula in analytical form is derived for the core layer in an optical planar waveguide by the thin-film approximation, which is based on a closed-form solution in multilayered isotropic structures off the edges. This formula indicates that elastic, thermal, and structural parameters can affect the magnitude of the stress. Using the formula, one can remove thermal stress and hence stress-induced birefringence by proper waveguide design.