Wavefront shaping of Bloch surface waves enabled by planar Bragg array couplers

Le résumé fourni par la source

The ability to freely shape the wavefront of surface waves is crucial for advancing on-chip photonics applications. However, the practical realization of devices capable of the arbitrary manipulation of Bloch surface waves (BSWs) remains a challenge. In this study, we design and fabricate a series of planar Bragg array couplers and experimentally demonstrate their ability to shape the wavefronts of excited BSWs. When a laser beam is incident from a glass substrate onto the Bragg array coupler at a predetermined angle, the coupler compensates for the momentum mismatch between the incident light and the target BSWs, thereby enabling precise control of the initial phase of the excited BSWs. This method can efficiently excite transverse magnetic polarized BSWs, making it possible to image the generated beams in the far field using a leakage radiation microscopy system. Using this approach, we successfully generate and observe well-defined BSW focusing, diffraction-free cosine-Gauss beams, and accelerating beams along pre-engineered trajectories. Moreover, the self-healing properties of the generated beams are demonstrated, confirming their robustness against local perturbations. These results establish a general platform for surface-wave manipulation, paving the way for the development of highly integrated on-chip photonic devices.

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