Oversized helical waveguides for optically pumped far-infrared lasers

Fibre lasers and related technologies

“…Alternatively, the polarisation dependence of the writing process, mostly due to the anisotropic core-cladding stress relief during UV exposure, can be used to permanently lock a helical distribution of index variation [33]. We have shown that the circularly induced birefringence resulting from oscillation within a resonator having a helical period larger than the Bragg period is akin to that of a helical DFB (HFB) laser, where the helix period is on dimensions of the required Bragg period for distributed lasing [34][35][36]. The fibre version is equivalent to a solid-state HFB laser.…”