Design of solid-core microstructured optical fiber with steering-wheel air cladding for optimal evanescent-field sensing

We present the design of a solid-core microstructured optical fiber with steering-wheel pattern of large holes in cladding as platform for evanescent-field sensing. Both geometry and optical properties of the fiber are numerical computed and analyzed in consideration of manufacturability using sol-gel casting technique as well as by evaluating a triangular lattice of holes with three rings in the design structure so that effective parameters can be established using effective step-index model. We predict less than 0.7 dB/m confinement loss at 850 nm, 29%, 13.7%, and 7.2% of light intensity overlap in air holes at 1500 nm, 1000 nm, and 850 nm wavelength, respectively, in such fiber. With the low loss and high mode-field overlap, the steering-wheel structured fiber is well suited for evanescent-field sensing and detection of chemical and biological species.