The University of Southampton

Peter Kazansky

Masaaki Sakakura

Yanhao Yu

Lei Wang

Martynas Beresna

Rokas Drevinskas

Ausra Cerkauskaite

Yuhao Lei

A method of fabricating an optical element includes providing a substrate of a transparent material in which is to be formed a plurality of birefringent nanostructures spaced apart; generating from the output of a source of femtosecond laser pulses a laser beam group comprising a plurality of focused seeding beams having a circular polarisation; directing the laser beam group onto the surface of the substrate at a first position and applying one or more femtosecond laser pulses from each beam to corresponding volumes in the substrate; repeatedly translating the laser beam group relative to the substrate parallel to the line of seeding beams; translating the laser beam group relative to the substrate and repeating the repeated translation and application of the femtosecond laser pulses; wherein the relative translation of the laser beam group and the substrate aligns the writing beam with successive corresponding volumes.

Method of forming birefringent structures in an optical element

A method of delivering optical pulses to a substrate comprises directing a focused beam from a source of optical pulses along a propagation direction onto a substrate; moving the substrate relative to the beam in a plane substantially orthogonal to the propagation direction and continuously along a first direction that includes spaced apart row locations on the substrate, and delivering a plurality of optical pulses from source as the beam reaches each row location; and between delivering the optical pulses at consecutive row locations, moving the beam relative to the substrate in one or more successive discrete movements along a second direction in the plane orthogonal to the first direction, to direct the beam to one or more spaced apart column locations on the substrate, and delivering a plurality of optical pulses from the source at each column location.

Method of optical pulse delivery to multiple locations on a substrate

A method of delivering optical energy to a substrate comprises applying a temporal group of optical pulses to a region of the substrate, wherein the temporal group comprises twenty or fewer pulses of a femtosecond pulse duration, arranged as a first subgroup of pulses comprising up to three pulses followed by a second subgroup of pulses comprising the remaining pulses in the temporal group; and wherein energies of the pulses are controlled such that pulses in the first subgroup have a first energy per pulse and pulses in a second subgroup of pulses have a second energy per pulse which is less than the first energy.

Method of pulsed laser irradiation with reduced thermal damage

An optical element for modifying an incident laser beam propagated through the optical element from an input face to an output face via a geometric phase birefringent effect, the optical element comprising: a substrate of a transparent amorphous material with an input face and an opposite output face; and a structural modification in a volume of the substrate between the input face and output face comprising a plurality of randomly positioned nanostructures; wherein each nanostructure has a oblate spheroidal shape with an elliptical cross section in a plane parallel to the input face, the elliptical cross-section having a minor axis substantially not larger than 30 nm and a major axis greater than the minor axis, and each nanostructure having a length in a direction perpendicular to the input face which is substantially not larger than 100 nm.

Nanostructured optical element, method for fabrication and uses thereof

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.

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Southhampton, United Kingdom

Peter Kazansky