Vector beams have been used in scientific and engineering researches due to their unique focusing properties. In recent years, many methods of generating the vector beams have been proposed, among which the spatial light modulator (SLM) is widely used based on the superposition principle with using orthogonally polarized beams. However, the energy waste is generally associated with these superposition methods. How to efficiently generate vector beams is still a hot topic. Recently, we proposed an efficient method to generate tunable vector beams by using two triangular common-path interferometers (TCPIs) as the beam splitting and combining system. However, due to the complex structure of the TCPI, the system is difficult to adjust and unstable. In addition, the optical system brings about a long optical path, and the vector beams consisting of non-eigen modes will be distorted obviously with a long distance propagation.
In this paper, an improved method is proposed. We replace the TCPIs with a pair of beam displacers, which act as a beam splitter and combiner, respectively. In this setup, we can arbitrarily manipulate the polarization states and phase distributions of vector beams in real time by managing the phase diagrams load on the SLM. The whole optical system does not involve any diffractive optical elements, and has a higher conversion efficiency. The improved optical system is compact and stable, and makes the adjustment of coaxiality easier. The light energy utilization depends mainly on the reflectivity of SLM. The efficiency of generating vector beams is increased to 58% by using an SLM with a reflectivity value of 79%. Several typical vector beams with phases and tunable amplitude, including cylindrical vector beams, fractional vector beams, and vector beams with double singularities, double-mode, radially variant polarization distribution, and azimuthally and radially variant polarization distribution, are generated and verified well experimentally. This method is also expected to create high-power vector beams and play an important role in laser processing and light trapping.
Project supported by the National Natural Science Foundation of China (Grant Nos. 11634010, 61675168, 11774289), the National Key Research and Development Program of China (Grant No. 2017YFA0303800), the Joint Fund of the National Natural Science Foundation of China and China Academy of Engineering Physics (Grant No. U1630125), the Basic Research Plan of the Natural Science Research Project of Shaanxi Province, China (Grant No. 2018JM1057), and the Seed Foundation of Innovation and Creation for Graduate Students in Northwestern Polytechnical University, China (Grant No. ZZ2018177).