High Resolution Spectral Metrology Leveraging Topologically Enhanced Optical Activity in Fibers

Optical rotation, a form of optical activity, is a phenomenon employed in various metrological applications and industries including chemical, food, and pharmaceutical. In naturally-occurring, as well as structured media, the integrated effect is, however, typically small. Here, we demonstrate that, by exploiting the inherent and stable spin-orbit interaction of orbital angular momentum fiber modes, giant, scalable optical activity can be obtained, and that we can use this effect to realize a new type of wavemeter by exploiting its optical rotary dispersion. The device we construct provides for an instantaneous wavelength-measurement technique with high resolving power $R =3.4 \times 10^6$ (i.e. resolution $< 0.3 pm$ at $1-{\mu}m$ wavelengths) and can also detect spectral bandwidths of known lineshapes with high sensitivity.