Passively Q-switched Nd:YAG microchip laser emits radially and azimuthally polarized light

In this paper a LD end-pumped Nd:YAG ceramic microchip laser passively Q-switched by Cr
⁴⁺
:YAG absorber is demonstrated to generate axisymmetrically polarized pulse. The reason to employ the end-pumped microchip laser lies in the fact that such cavity configuration is beneficial carrier both for producing energetic Q-switched pulse and also the axisymmetrical polarization. The Cr
⁴⁺
:YAG crystal absorber has an initial transmission of 95% and was antireflection-coated at both sides. A photonic crystal grating (PCG) was deployed as an output coupler to force radial- or azimuthal-polarization oscillation. The length of laser was 5.5 cm, and the distance between the grating and the absorber was 5 mm.