All-optically phase-induced polarization modulation by means of holographic method

Ziyao Lyu,Changshun Wang

doi:10.1038/s41598-020-62549-z

Abstract

Phase-induced polarization modulation has been achieved experimentally by means of the all-optical holographic method. An extra spiral phase is added to a Gaussian beam and then a holographic grating is recorded through the interference of a Gaussian beam and the phase-vortex beam with the same linear polarization state in an azobenzene liquid-crystalline film. We report here that the polarization state of the diffraction light from the recorded grating is different from that of the incident light, while no polarization variation occurs for the holographic grating recorded by two Gaussian beams. The phase-induced polarization modulation is mainly attributed to the formation of birefringence in the film generated by phase vortex, which is investigated through the ripple patterns resulting from the competition between photoinduced torques and analysed by the Jones matrix. The experimental results could enrich the connotation between optical parameters and offer a method to realize polarization modulation through phase control.

Highlights

Phase-induced polarization modulation has been achieved experimentally by means of the all-optical holographic method
It is found that the polarization state of the diffraction light from vortex-based grating (VBG) changes asynchronously with the incident polarization state being manipulated, indicating that the optical polarization state is modulated by the recorded grating
The VBG is recorded by means of the holographic interference of a Gaussian beam and a phase-vortex beam, resulting in the formation of the periodically distributed photoinduced anisotropy in the azobenzene liquid crystals (ALC) film

Summary

Introduction

Phase-induced polarization modulation has been achieved experimentally by means of the all-optical holographic method. An extra spiral phase is added to a Gaussian beam and a holographic grating is recorded through the interference of a Gaussian beam and the phase-vortex beam with the same linear polarization state in an azobenzene liquid-crystalline film. During the holographic recording process, the azobenzene polymer is illuminated by two or more polarized interference beams, leading to the azobenzene groups reorienting perpendicularly to the polarization direction of light field and the formation of the photoinduced anisotropy, which is believed to result from the trans–cis–trans isomerization cycles of the azo-unit[22,23]. The polarization state of the diffraction light is not able to be modulated in terms of the holographic grating recorded by the interference of two Gaussian beams with the same polarization state.

Methods

Results

Conclusion