Azimuthally polarized, passively Q-switched Yb-doped fiber laser

Radially polarized and passively Q-switched Yb-doped fiber laser based on intracavity birefringent mode discrimination

“…The predicted switching of the laser beam from radial polarization to azimuthal polarization did not happen. This phenomenon was identical to our previous report [20,22], in which we obtained azimuthally polarized output and the switching of the laser beam from azimuthal polarization to radial polarization did not occur. Figure 6 shows the captured intensity distributions of laser beams at P abs = 6.48 W when moving the SA away from the optimum position.…”

“…As seen in figure 9 (a), the pulse envelope was slightly modulated by the spikes, with a period of 12.9 ns; this was identical to the cavity round-trip time. This self-mode-locking phenomenon has been observed in passively and actively Q-switched fiber lasers [18,20,23,24] and also in the self-pulsed fiber laser [25]; usually, this phenomenon was attributed to the mode beats between axial modes of the cavity, and was supported by further mode coupling caused by self-phase modulation [26].…”

“…The adoption of a single lens not only induced the efficient spatial walk-off inside the c-cut YVO 4 crystal, but it also favored the saturation of SA by converging the intra-cavity photon fluence inside the Cr 4+ :YAG crystal. The difference of this study from [20] is in the variation of the length of the used gain fiber, and that the laser emitted radially polarized output; thus, this study reflected that one specific length of gain fiber was associated with radially or azimuthally polarized outputs. The details of our study are given as follows.…”

“…Compared with the PCG mirror, the birefringent crystal is low-cost and available everywhere; the spatial walkoff inside it can discriminate the vector mode's excitation of one laser resonator in a wide wavelength range and the output polarization is switchable [14]. Based on this method, we combined a birefringent crystal with a single-lens imaging system for intracavity mode selection, and presented an azimuthally polarized and passively Q-switched fiber laser [20]. This laser was highly efficient with several watts of laser power, and for the first time the birefringent walk-off mode-selective mechanism exhibited power scalability when applied for a vector fiber laser.…”

Generation of polarization and phase singular beams in fibers and fiber lasers

“…Different from standard laser beams or natural lights, CVBs exhibit axially symmetric polarizations in the spatial domain. [45][46][47] As shown in Figs. 1(c)-1(e), depending on the spatial distribution of the polarization, CVBs can be classified as RPBs, APBs, and hybridly polarized beams.…”