A Polarimetric Interferometer Based on Composite Optical Waveguide for Refractive Index Detection

A sensitive interference refractive index sensor based on composite optical waveguide (COWG) was developed. Sol-gel technique was used to prepare TiO2 sol, and the TiO2 film was fixed on the surface of single-mode potassium ion-exchange (PIE) optical waveguide (OWG) by dip-coating and annealing treatment to fabricate an interference refractive index sensor device. The interference between the zeroth-order transverse electric (TE0) and magnetic (TM0) modes of the laser beam which transport in the COWG caused phase-difference change (Δ) of output light signals. Refractive index sensitivity of TiO2/PIE COWG chip was examined by injecting aqueous NaCl solutions and distilled water in turn to detect its Δ. Experimental results show that, for the TiO2/PIE COWG its refractive index sensitivity is SRI = (573.09 × 2π)/RIU in the refractive index ranges of 1.3386~1.36. The sensor sees the advantages of high sensitivity, compact size, simple fabrication, as well as low cost.