Integrated Terahertz Petal‐Like Beam Emitter via Defect‐Induced Backscattering

ABSTRACT Petal‐like beams are gaining interest for applications like angular velocity detection, display, sensing, communication, and particle manipulation. This study presents a petal‐like beam emitter using a resonator with defect‐induced backscattering. The generation of petal‐like spatial profiles is theoretically analyzed and can be conceptualized as an overlap of two beams with opposing topological charges. Unlike other methods, this device, owing to the co‐excitation of clockwise (CW) and counter‐clockwise (CCW) modes within the cavity, eliminates the need for the consideration of beam waist and alignment of the vortex beams with opposite topological charges when generating a petal‐like beam. Simulations show the spatial intensity profiles of the petal‐like beam can be effectively controlled by adjusting the defect's slit depth and width, as well as the resonator excitation conditions. A comparative analysis with defect‐free devices confirms the critical role of the defect structure in beam shaping. We utilized a near‐field detection system to probe the electric field intensity and phase distribution of petal‐like beams with topological charges of ±1 to ±3 at terahertz (THz) frequencies. The proposed methodology provides a simple and adaptable approach to generating petal‐like beams with multiple spatial modes, thereby enhancing their potential for applications such as THz sensing, measurement, and communication.