Synthesis of light needles with tunable length and nearly constant irradiance

Rosario Martínez-Herrero,David Maluenda,Ignasi Juvells,Artur Carnicer

doi:10.1038/s41598-018-21007-7

Rosario Martínez-Herrero, David Maluenda + Show 2 more

Open Access

https://doi.org/10.1038/s41598-018-21007-7

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Abstract

We introduce a new method for producing optical needles with tunable length and almost constant irradiance based on the evaluation of the on-axis power content of the light distribution at the focal area. According to theoretical considerations, we propose an adaptive modulating continuous function that presents a large derivative and a zero value jump at the entrance pupil of the focusing system. This distribution is displayed on liquid crystal devices using holographic techniques. In this way, a polarized input beam is shaped and subsequently focused using a high numerical aperture (NA) objective lens. As a result, needles with variable length and nearly constant irradiance are produced using conventional optics components. This procedure is experimentally demonstrated obtaining a 53λ-long and 0.8λ-wide needle.

Highlights

About sixty years ago, McLeod[1] introduced conical lenses as a way to produce light axicons
This paper is organized as follows: first, after introducing key concepts in propagation of light at the the focal area, we propose a mathematical framework for producing long needles with almost constant irradiance
Es is described as the product of the illuminating beam profile g(θ) (with polarization p(φ)) and a certain modulation function h(θ) that is used to tailor the beam according to the requirements of the problem

Summary

Introduction

McLeod[1] introduced conical lenses as a way to produce light axicons. The incident beam is tailored by means of a special continuous modulating function designed to maximize the length of the needle according to on-axis irradiance considerations. This distribution is experimentally implemented by means of digital holography. We produced in the laboratory a 53λ-long and 0.8λ-wide needle These values are only limited by the characteristics of the electronic devices used in the optical setup. This paper is organized as follows: first, after introducing key concepts in propagation of light at the the focal area, we propose a mathematical framework for producing long needles with almost constant irradiance. In the Methods section we provide mathematical details on the design properties of the modulation function

Methods

Results

Conclusion