“…If typical index-guiding PCFs are infiltrated with liquid crystals, they start guiding light by the bandgap effect, since liquid crystals have refractive indices higher than that of silica. Based on liquid crystal filled PCFs (LCPCF), devices which can be thermally, electrically or optically tuned, have been demonstrated [9][10][11][12][13][14][15][16][17][18][19][20]. Among these, we find, for example, devices for tuning, scrambling and controlling the polarization [11,19] tunable Gaussian filters for Optical Coherence Tomography (OCT) [14], tunable electrically and mechanically induced gratings [15], tunable notch filters [16], devices with tunable birefringence [18] and devices for single-polarization and high-birefringence guidance [20].…”