A 1.6 µm dual-channel cylindrical vector laser enabling multi-state shift keying

A 1645 nm end-pumped dual-channel Er:YAG vector laser that could generate two cylindrical vector (CV) beams simultaneously with different polarization orders is demonstrated. The laser is designed in a two-arm structure, wherein each arm places a q-plate (QP) to introduce intra-cavity spin-orbital angular momentum conversion, leading to the oscillation of two various CV modes in two arms, and finally output along two directions, respectively. The favorable experimental results illustrate high power stability and polarization mode purity. Furthermore, an additional setup is built to demonstrate the potential of the proposed dual-channel CV laser in data transmission. By placing additional acousto-optic modulators, the output dual CV modes are encoded to represent different digital symbols and achieve successful data transmission in free space.