Design and Experimental Research of Vortex Beam Mixer

Based on the birefringence phenomenon of vortex beam in uniaxial crystals for optical path design, yttrium vanadate crystals and waveplates are used to realize coherent mixing of vortex beam. A crystal-type spatial light mixer applied to a vortex beam communication system is designed. The effects of beam polarization, waveplate optical axis, crystal transmittance, and other factors on the performance of the mixer are explored. Simulations show that the mixer output phase error is extremely small, the insertion loss is about 1.9 dB , and the overall loss is close to 36.6%. Finally, it is applied in the vortex optical coherent communication system, and the effectiveness of the optical mixer is experimentally verified with a phase deviation of 3°, a splitting ratio close to 1, and a mixing efficiency of 78.5%. Vortex beam mixer extracts information such as phase, amplitude, and polarization of the signal light by combining optical beams with orbital angular momentum modes. It enables mode multiplexing, topologically protected transmission, and high-order modulation. This technology is widely applied in space optical communication, high-speed fiber-optic systems, and quantum communication.