Research on terahertz bessel beams based on metasurface

Abstract

Traditional terahertz imaging systems are constrained by a limited depth of field, which leads to blurry images outside the focal point. To address this limitation, we designed a metasurface with rectangular pillar-structured units based on the transmission phase using a ceramic slurry. Using the finite-difference time-domain method for calculations and simulations, the arranged metasurface unit cells in a ring configuration produced a Bessel beam with a non-diffracting distance of 30 mm. The study found that the phase gradient, light source divergence angle, material refractive index variation, and processing errors influenced the beam propagation characteristics. Notably, the phase gradient and light source divergence angle are directly proportional to the non-diffracting distance and significantly affect the performance of imaging system. The metasurface designed in this study enhances the depth of field of terahertz imaging systems and offers novel insights into the manipulation and application of terahertz beams. This innovation has potential applications in fields such as terahertz imaging and nondestructive testing.