High-birefringence hollow-core fibers and techniques for making same

A hollow core fiber comprising:

• a cladding comprising a matrix of cells, each cell comprising a hole and a wall surrounding the hole, and
• a hollow core region comprising a core gap in the matrix of cells, wherein the core gap spans a plurality of cells and has a core gap boundary defined by an interface between the cells of the core gap and the cells of the cladding,
• wherein the matrix of cells comprises
• a plurality of lattice cells, and
• a plurality of defect cells, wherein the defect cells are characterized by one or more differences in at least one property from that of the lattice cells, and
• wherein the cells at the core gap boundary include defect cells so as to produce birefringence in a light propagating through the hollow core fiber,
• wherein respective wall thicknesses of the defect cell and the lattice cell satisfy a relationship:
• (
• 1
• -
• AFF
• defect
• )
• (
• 1
• -
• AFF
• lattice
• )
• =
• 0.5
• ⁢
• ⁢
• to
• ⁢
• ⁢
• 0.9
• wherein AFFdefect is the proportion by volume of air to optical material in at least one defect cell and AFFlattice is the proportion by volume of air to optical material in at least one lattice cell.

A hollow core fiber comprising:

• a cladding comprising a matrix of cells, each cell comprising a hole and a wall surrounding the hole, and
• a hollow core region comprising a core gap in the matrix of cells, wherein the core gap spans a plurality of cells and has a core gap boundary defined by an interface between the cells of the core gap and the cells of the cladding,
• wherein the matrix of cells comprises
• a plurality of lattice cells, and
• a plurality of defect cells, wherein the defect cells are characterized by one or more differences in at least one property from that of the lattice cells, and
• wherein the cells at the core gap boundary include defect cells so as to produce birefringence in a light propagating through the hollow core fiber,
• wherein respective wall thicknesses of the defect cell and the lattice cell satisfy a relationship:
• (
• 1
• -
• AFF
• defect
• )
• (
• 1
• -
• AFF
• lattice
• )
• =
• 1.1
• ⁢
• ⁢
• to
• ⁢
• ⁢
• 2.0
• wherein AFFdefect is the proportion by volume of air to optical material in at least one defect cell and AFFlattice is the proportion by volume of air to optical material in at least one lattice cell.

A method for fabricating a birefringent hollow core fiber comprising the steps of:

• arranging a plurality of capillary tubes into a matrix of a preform assembly;
• providing a core gap in the matrix, wherein the core gap spans a plurality of tubes and has a core gap boundary defined an interface between the core gap and the remaining assembly,
• wherein the matrix comprises
• a plurality of lattice capillary tubes, and
• a plurality of defect capillary tubes characterized by one or more differences in at least one property from that of the capillary tubes, and
• wherein the capillary tubes at the core gap boundary include defect capillary tubes that are arranged in a pattern for forming a hollow core fiber from the preform assembly;
• and
• drawing the preform assembly into a fiber, wherein the assembly fuses together to form a hollow core corresponding to the core gap and a microstructured cladding having individual cells corresponding to individual capillary tubes in the preform assembly,
• wherein at least one the plurality of defect capillary tubes has a different cross sectional solid area compared with that of at least one of the plurality of capillary tubes.

A method for fabricating a birefringent hollow core fiber comprising the steps of:

• arranging a plurality of capillary tubes into a matrix of a preform assembly;
• providing a core gap in the matrix, wherein the core gap spans a plurality of tubes and has a core gap boundary defined an interface between the core gap and the remaining assembly,
• wherein the matrix comprises
• a plurality of lattice capillary tubes, and
• a plurality of defect capillary tubes characterized by one or more differences in at least one property from that of the capillary tubes, and
• wherein the capillary tubes at the core gap boundary include defect capillary tubes that are arranged in a pattern for forming a hollow core fiber from the preform assembly;
• and
• drawing the preform assembly into a fiber, wherein the assembly fuses together to form a hollow core corresponding to the core gap and a microstructured cladding having individual cells corresponding to individual capillary tubes in the preform assembly,
• wherein respective wall thicknesses of the defect capillary tubes and the lattice capillary tube satisfy a relationship:
• (
• 1
• -
• AFF
• defect
• )
• (
• 1
• -
• AFF
• lattice
• )
• =
• 0.5
• ⁢
• ⁢
• to
• ⁢
• ⁢
• 0.9
• wherein AFFdefect is the proportion by volume of air to optical material in at least one defect capillary tube and AFFlattice is the proportion by volume of air to optical material in at least one lattice capillary tube.

A method for fabricating a birefringent hollow core fiber comprising the steps of:

• arranging a plurality of capillary tubes into a matrix of a preform assembly;
• providing a core gap in the matrix, wherein the core gap spans a plurality of tubes and has a core gap boundary defined an interface between the core gap and the remaining assembly,
• wherein the matrix comprises
• a plurality of lattice capillary tubes, and
• a plurality of defect capillary tubes characterized by one or more differences in at least one property from that of the capillary tubes, and
• wherein the capillary tubes at the core gap boundary include defect capillary tubes that are arranged in a pattern for forming a hollow core fiber from the preform assembly;
• and
• drawing the preform assembly into a fiber, wherein the assembly fuses together to form a hollow core corresponding to the core gap and a microstructured cladding having individual cells corresponding to individual capillary tubes in the preform assembly,
• wherein respective wall thicknesses of the defect capillary tubes and the lattice capillary tube satisfy a relationship:
• (
• 1
• -
• AFF
• defect
• )
• (
• 1
• -
• AFF
• lattice
• )
• =
• 1.1
• ⁢
• ⁢
• to
• ⁢
• ⁢
• 2.0
• wherein AFFdefect is the proportion by volume of air to optical material in at least one defect capillary tube and AFFlattice is the proportion by volume of air to optical material in at least one lattice capillary tube.