Liquid Crystal Lensacons, Logarithmic and Linear Axicons

Abstract

Until now, several attempts have been made to obtain axicons by using liquid crystals. Previous results had always a considerable deviation from the linear response and the resulting aperture is square. In addition, classical fabrications methods are expensive and only produce fixed phase profiles. In this study, a novel structure to obtain tunable axicons with a perfect conical shape and a circular aperture is proposed and theoretically studied. The proposed optical device is based on nematic liquid crystal and phase shifted electrical signals. A simulation program consisted of Finite Elements Method to solve the voltage distribution combined with the Frank-Oseen equation to solve the molecular position of the nematic liquid crystal is employed. This device is totally reconfigurable by using low voltage signals. The focus depth and the position of this one can be controlled electrically.

Positive-negative tunable liquid crystal lenses based on a microstructured transmission line

“…Specifically, LC-tunable optical phase modulation is one of the most important uses, which has attracted significant attention for years 1 . Currently, it is a very researched topic, for example in ophthalmological applications 2 , 3D vision applications [3][4][5][6] , beam steering 7 , optical vortices [8][9][10][11] , tunable zooming 12 , aberration correctors 13 , astronomy 14 , novel aberration correctors 15 , multi-optical elements 16 , micro-axicon arrays 17 , multi-focal 18 , high fill-factor 19 and frequency controlled 20 microlenses, lensacons, and logarithmic axicons 21 , etc. High among those are adaptive-focus lenses, which were first proposed more than 40 years ago and still are a hot topic.…”

“…In the case of Fig. 6(a), the voltage is linear at the sides producing axicon-type lenses 21 . When the voltage is high enough a logarithmic lens is produced [see Fig.…”

“…When the voltage is high enough a logarithmic lens is produced [see Fig. 6 voltage configuration (d)] 21 . For the case of linear resistance, Fig.…”

Multifrequency Driven Nematics

“…This dependence gives raise to the possibility of designing liquid crystal mixtures with very low relaxation frequencies of electric permittivity parallel ε , which is useful for many applications [16]. Apart from traditional SLM, the unique properties of this LC mixture can be used in all kind of optical phase modulators recently reported, e.g., adaptive lenses [17], beam steering [18], correction of aberrations [19], 3D vision applications [19][20][21][22], novel aberrations correctors for rectangular apertures [23], microaxicon arrays [24], multioptical elements [25], hole-patterned microlenses [26], multifocal microlenses [27], high fill-factor microlenses [28], frequency controlled [29] microlenses, optical vortices [30], lensacons, and logarithmic axicons [31]. The LC mixtures used in this work have been designed by mixing three different families of LC compounds to meet the requirements of the LC to be controlled by low frequencies of the electrical applied voltage.…”

Tunable Axicons Generated by Spatial Light Modulator with High-Level Phase Computer-Generated Holograms

“…Sometimes with the need of changing measurement ranges, it has to replace axicons with different refractive angles or tune the cone angle (refractive angle) of the axicon. It is not convenient to replace the axicon and adjust the optical path, and it is a difficult task to vary the cone angle [8]. The fabrication errors of the axicon will also influence the quality of the nondiffracting beams and its applications.…”