The use of bulge-like microcavities in microcavity sensors provides advantages in alignment and reproducibility in manufacturing. Arrays of bulge-like microcavities may be used with multiple waveguides. In addition, the bulge-like microcavity may be formed with at least an outer layer made of a polymer material, and may be made entirely from polymer material. This facilitates manufacturing in that the microcavity may be molded, and may also be reproducibly molded in an array configuration.