Optimizing terahertz generation via axial-length controllable filaments with spatial light modulator

Le résumé fourni par la source

Terahertz wave can be produced from two-color laser induced filaments, whose length is one of the critical factors that determine the output yield. Here, we propose a new method to generate the axial-length controllable filament using a liquid crystal spatial light modulator (LC-SLM). Previous studies have employed optical elements such as phase plates and deformable mirrors to optimize and control the filamentation process, but these methods lack flexibility. Our approach enables the programmable modulation of the phase distribution and spatial distribution using SLM. By loading a diffraction phase pattern, it enables convenient manipulation of the length, diameter, electron density of the plasma filament, while also providing advantages in flexibility and feedback optimization for improving terahertz output. Moreover, we demonstrate how the fan-shaped segmentation phase method can be applied to generate air plasma and control the length of the filament to enhance terahertz output. Our method can overcome the saturation effect induced by plasma clamping, therefore improve the terahertz output. To verify its feasibility, we establish a far-field distribution model for terahertz yield based on the photo-current model and investigate the effect of filament length on terahertz output under different conditions. The simulation results show that our method can significantly improve terahertz output at different frequencies and initial phase of the two-color field. Overall, our approach offers a relative simple and effective way to control the length of plasma filaments and enhance terahertz output using SLM technology, it has great potential applications in terahertz biophysics.

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