# US 2014/0153097 A1 · Space variant polarization converter

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- Number: US 2014/0153097 A1
- Document ID: US20140153097A1
- Status: Published application
- Kind: A1
- Application number: 14/115,300
- Filed: 2012-05-03
- Published: 2014-06-05
- Earliest claimed: 2011-05-03
- Assignees: University of Southampton
- Applicants: University of Southampton
- Inventors: Martynas Beresna; Peter Kazansky
- Web page: https://patentgrep.com/patent/US20140153097A1

## CPC

- G02B 5/3083: {Birefringent or phase retarding elements (G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001)}
- G02B 5/1809: {with pitch less than or comparable to the wavelength}
- G02B 27/286: {for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another (G02B5/3083 takes precedence; light guide coupling means utilising polarising elements G02B6/34)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

This patent describes an optical element, which converts incident linearly or circularly polarized visible light into radially or azimuthally polarized light beam. The polarization converter is a single optical element, produced by direct laser writing technique in an optically transparent substrate. Direct laser writing based on ultra-short pulsed laser radiation forms form birefringence self-assembled nanogratings in optically transparent material, such as fused silica. The period of gratings is smaller than wavelengths of a visible light.

## Claims

### Claim 1

An optical device comprising:
the optical device for converting an entry light beam into an exit light beam with a defined spatial distribution of polarization states,
wherein the optical device includes at least laser induced birefringence structures formed in the bulk of a transparent optical substrate over at least a portion of the clear aperture sufficient to produce an optical retardance.

### Claim 2 (depends on 1)

The optical device according to claim 1, wherein said birefringence structures are subwavelength gratings, formed by ultra-short pulse direct laser writing.

### Claim 3 (depends on 1)

The optical device according to claim 1, wherein said subwavelength gratings are self-assembled nanogratings, formed by ultra-short laser pulses.

### Claim 4 (depends on 1)

The optical device of according to claim 1, wherein the clear aperture region of the optical element exhibits a smoothly varying principal form direction such that the form birefringence varies smoothly.

### Claim 5 (depends on 1)

The optical device according to claim 1, wherein the optical element is arranged as a half-wave plate with continuously varying slow axis direction to convert incoming linearly polarized beam to a radially or azimuthally polarized beams.

### Claim 6 (depends on 1)

The optical device according to claim 1, wherein the optical element is arranged as a quarter-wave plate possessing a radial symmetry to convert incoming circularly polarized beam to a radially or azimuthally polarized vortices.

### Claim 7 (depends on 1)

The optical device according to claim 1, wherein the radial or azimuthal polarizations are obtained with the same birefringent optical element by changing handedness of the incident circular polarization.

### Claim 8

A method comprising:
producing the polarization converter for converting a circularly or linearly polarized entry light beam into an exit light beam having radial or azimuthal polarization,
wherein form birefringent optical structures are induced by ultra-short pulse laser radiation.

### Claim 9 (depends on 1)

An optical system for improved resolution imaging of an object, comprising:
at least an illumination source that provides spatially homogeneously polarized light along an illumination path, including a first space variant waveplate in the illumination path on an object side of the system according to claim 1.

### Claim 10 (depends on 1)

An optical system for laser material processing, comprising:
at least a laser source with homogeneously polarized beam, including a space variant waveplate in the laser beam path of the system according to claim 1.

### Claim 11 (depends on 8)

The method of claim 8, when the ultra-short pulse laser radiation includes a picosecond or femtosecond laser radiation.