Fabrication of long range periodic nanostructures in transparent or semitransparent dielectrics

A method of making a Bragg grating comprising:

• providing a transparent or semi-transparent substrate;
• generating a linearly polarized, pulsed laser beam, said laser beam having a pulse energy exceeding a predetermined energy threshold (Eth) that is dependent on the nature of the substrate;
• bringing said laser beam to a focus within the body of said transparent or semi-transparent substrate;
• and
• scanning said transparent or semi-transparent substrate with said linearly polarized laser beam along a scanning path to create sub-diffraction limit structures comprising periodic slabs of modified material oriented orthogonal to the direction of the laser polarization and extending along said scanning path in said transparent or semi-transparent substrate.

A method of making a Bragg grating inside a waveguide, comprising:

• providing an optical waveguide with a core, said optical waveguide having a propagation direction;
• generating a linearly polarized, pulsed laser beam, said laser beam having a pulse energy exceeding a predetermined energy threshold (Eth) dependent on the nature of the substrate;
• bringing said laser beam to a focus within said core;
• and
• scanning said core with said linearly polarized laser beam along the propagation direction of the waveguide to create sub-diffraction limit structures comprising periodic nano-gratings oriented orthogonal to the direction of the laser polarization and extending along said propagation direction.

A method of making connected nanovoids in a transparent or semi-transparent substrate, comprising:

• generating a circularly polarized pulsed laser beam or a linearly polarized beam with the laser polarization perpendicular to the scan direction, said laser beam having an energy exceeding a predetermined energy threshold for nanovoid formation dependent on the nature of the substrate;
• bringing said laser beam to a focus within the body of said transparent or semi-transparent substrate;
• and
• scanning said transparent or semi-transparent substrate with said circularly or linearly polarized laser beam along a scanning path to induce material modification with the formation of connected sub-diffraction limited nanovoid structures.

A method of processing a transparent substrate, comprising:

• generating a pulsed polarized laser beam having a pulse duration less about 50 fs and having an energy exceeding a predetermined energy threshold for the onset of uniform modification but less than a predetermined energy threshold for periodic nanostructure formation dependent on the nature of the substrate;
• bringing said laser beam to a focus within the body of said transparent substrate;
• and
• scanning said transparent substrate with said polarized laser beam along a scanning path to induce uniform material modification without the formation of sub-diffraction limit nanostructures or to remove such nanostructures present in said substrate.