Structured light engineering using a photonic nanojet

TL;DR

This paper demonstrates how photonic nanojets, generated by spheroid-shaped focusing elements, can be used to engineer the far-field light distribution in structured light systems, with experimental and numerical validation.

Contribution

It introduces the use of spheroid geometries to generate photonic nanojets for controlling far-field light patterns in structured illumination systems.

Findings

Photonic nanojets can be engineered by spheroid shape modifications.

Nanojets with higher divergence angles increase the field of view.

Experimental results confirm numerical simulations of pattern control.

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.