Tunable Yb3+ laser based on an isotropic fibre with an anisotropic acoustooptic filter built into the resonator without accompanying polarisation losses with the help of a new polarisation beamsplitter

Tuning of a Yb³⁺-doped fibre laser based on an isotropic fibre with an anisotropic acoustooptic (AO) filter built into a resonator without accompanying polarisation losses with the help of a new dispersion-free thermostable single-crystal polarisation beamsplitter is studied in the cw regime. The maximum tuning range of the laser line of width 0.1 – 0.12 nm was 94 nm. Due to longitudinal mode locking caused by random coincidences of AO frequency shifts with multiple intermode distances of the laser resonator, the spike-mode oscillation was observed. When the resonator length was increased 10 times, cw lasing appeared, the residual root-mean-square noise was ~1.2%, and the laser linewidth was ~0.2 nm.