Polarization angle rotation sensing via mode superposition in a hollow-core fiber with two-fold symmetry

• Polarization angle sensor utilizing a tubular hollow-core fiber with a two-fold symmetric cladding; • Sensing principle relying on the superposition of LP 01 and LP 11 -like modes; • Fiber output intensity profile dependent on the incident light’s polarization angle; • Platform adaptable for a wider range of transduction scenarios, including electric field or chiral molecule sensing. Hollow-core photonic crystal fibers (HCPCF) have recently matured into a versatile platform for light guidance, offering properties such as ultralow loss and specific modal operation. By modifying the HCPCF cladding symmetry, it is possible to control the modal loss hierarchy and facilitate the propagation of specific higher-order modes. In this context, we here demonstrate the realization of an angle sensor utilizing a tubular HCPCF with a two-fold symmetric cladding. This specific fiber design enables the generation of an output intensity profile resulting from the superposition of LP 01 and LP 11 -like modes, whose excitation and resulting output intensity distribution are dependent on the polarization angle of the incident light. Thus, by rotating the input beam’s polarization and analyzing the evolution of the resulting output profile, we characterized a polarization rotation angle sensor exhibiting a sensitivity of (25 ± 1) counts/degree and an estimated resolution of 0.4°. We understand that this work broadens the framework of HCPCF applications, demonstrating that symmetry-modified hollow-core fibers can act as a promising platform for advanced sensing scenarios and polarimetric characterizations.