Structured light engineering using a photonic nanojet (2103.17179v1)

Abstract: In this letter, we present the photonic nanojet as a phenomenon in a structured light generator system that is implemented to modify the source focal spot size and emission angle. The optical system comprises a microlens array that is illuminated by a focused Gaussian beam to generate a structured pattern in the far-field. By introducing a spheroid with different aspect ratios in the focus of the Gaussian beam, the source optical characteristics change and a photonic nanojet is generated which will engineer the far-field distribution. To probe the light fields we implement a high-resolution interferometry setup to extract both the phase and intensity at different planes. We both numerically and experimentally demonstrate that the pattern distribution in the far-field can be engineered by photonic nanojet. As an example, we examine prolate, sphere, and ablate geometries. An interesting finding is that depending on the spheroid geometry, a smaller transverse FWHM of a photonic nanojet with a higher diverges angle produces an increased pattern field of view at the same physical size of the optical system.