Supported microfiber loops for optical sensing.

We demonstrate refractive-index sensors based on copper-rod- supported microfiber loops. Due to the robustness of the supported loop structure and the flexibility of obtaining critical coupling within a broad spectral range, these microfiber loops show high sensitivity and high stability for sensing in both low- and high-concentration solutions with estimated sensitivity of refractive-index measurement up to 1.8 x 10(-5).