Effective area measurement of few-mode fiber using far field scan technique with Hankel transform generalized for circularly-asymmetric mode.

We report on a measurement method for the effective area of the few-mode fiber. We derived a transform equation between a near-field pattern and a far-field pattern generalized for circularly-asymmetric higher-order modes of a cylindrical core, and enabled effective area measurement of the higher-order modes using high-dynamic-range far-field scan technique and low-crosstalk mode multiplexer. The measured effective area values agreed well with the values that were numerically predicted using a finite-element method from the refractive index profile, when the modal crosstalk was suppressed.

Resonant-wavelength tuning of a nanocavity by subnanometer control of a two-dimensional silicon-based photonic crystal slab structure.

We demonstrate fine tuning of the resonant wavelength of a nanocavity in a two-dimensional silicon-based photonic crystal slab structure by subnanometer control of the airhole diameter and slab thickness. Theoretical investigation shows that the resonant wavelength depends linearly on the latter two parameters. To experimentally demonstrate the fine tuning of the resonant wavelength, we control these parameters through chemical processes.