Optical activity (OA) is the rotation of the polarization orientation of the linearly polarized light as it travels through certain materials that are of mirror asymmetry, including gases or solutions of chiral molecules such as sugars and proteins, as well as metamaterials. The necessary condition for achieving OA is the birefringence of two circular polarizations in material. Here, we propose a new kind of self-accelerated OA in free space, based on the intrinsic Gouy phase induced mode birefringence of two kinds of quasi-non-diffracting beams. We provide a detailed insight into this kind of self-accelerated OA by analyzing angular parameters, including angular direction, velocity, acceleration, and even the polarization transformation trajectory. As the Gouy phase exists for any wave, this kind of self-accelerated OA can be implemented in other waves beyond optics, from acoustic and elastic waves to matter waves.

We propose an efficient and robust method to generate tunable vector beams by employing a single phase-type spatial light modulator (SLM). With this method, a linearly polarized Gaussian beam can be converted into a vector beam with arbitrarily controllable polarization state, phase, and amplitude. The energy loss during the conversion is greatly reduced and depends mainly on the reflectivity of the SLM. We experimentally demonstrate that conversion efficiency of about 47% is achieved by using an SLM with reflectivity of 62%. Several typical vector beams, including cylindrical vector beams, vector beams on higher order Poincaré spheres, and arbitrary vector beams attached with phases and with tunable amplitude, are generated and verified experimentally. This method is also expected to create high-power vector beams and play important roles in optical fabrication and light trapping.

Polarization oscillating beams, namely, polarization standing waves, commonly formed by a pair of coherent counterpropagating light waves with orthogonal polarizations, oscillate their states of polarization periodically within a wavelength interval, offering conceptual and practical interests in light-matter interactions such as the nonreciprocal magnetoelectric effect, and impressive applications in optical imaging, sensing, and chirality detection. Here, we propose a new class of polarization oscillating beams that longitudinally vary states of polarization with spatial intervals within centimeters via the superposition of two copropagating optical frozen waves with preshaped longitudinal intensity profiles and transverse phase structures. The flexibility and manipulability are demonstrated by creating several polarization oscillating beams with different polarization structures. This work paves a new way to manipulate other waves and may be useful for applications of optical standing waves in optical manipulation, light guiding of atoms, polarization-sensitive sensing, etc.