A method of manufacturing a preform, the method including positioning at least one glass tube in a glass outer cladding to form a preform precursor, the glass tube comprising a first open end and a second open end, forming a preform from the preform precursor, and thermally treating at least one of the preform precursor and the preform. The thermally treating including sealing the first open end and the second open end of the glass tube to form a closed tube and heating and/or cooling the glass tube to manipulate gas pressure within the closed glass tube.

A method of manufacturing a hollow core optical fiber, the method including positioning at least one glass tube in a glass outer cladding to form a preform precursor, the glass tube comprising a first open end and a second open end, and forming a preform from the preform precursor. The method further including drawing the preform into a hollow core optical fiber and, while drawing the preform, thermally treating the preform to manipulate gas pressure within the glass tube by at least one of (i) heating at least a portion of the preform to increase gas pressure within the glass tube and (ii) cooling at least a portion of the preform to decrease gas pressure within the glass tube.

A hollow core photonic crystal fiber (PCF) including an outer cladding region and seven hollow tubes surrounded by the outer cladding region. Each of the hollow tubes is fused to the outer cladding to form a ring defining an inner cladding region and a hollow core region surrounded by the inner cladding region. The hollow tubes are not touching each other but are arranged with distance to adjacent hollow tubes. The hollow tubes each have an average outer diameter d2 and an average inner diameter d1, wherein d1/d2 is equal to or larger than about 0.8, such as equal to or larger than about 0.85, such as equal to or larger than about 0.9. Also, a laser system.

Air core optical fiber structures in which the cladding is composed of an engineered optical metamaterial having a refractive index less than unity for at least one specific wavelength band and provides for total internal reflection of optical energy between the air core and metamaterial cladding. According to certain examples, a method of guiding optical energy includes constructing a hollow core optical fiber with an all-dielectric optical metamaterial cladding, coupling optical energy into the optical fiber having an operating wavelength near a resonance of the metamaterial cladding, and guiding the optical energy within the hollow core optical fiber by total internal reflection.

A hollow core photonic crystal fiber (PCF) including an outer cladding region and seven hollow tubes surrounded by the outer cladding region. Each of the hollow tubes is fused to the outer cladding to form a ring defining an inner cladding region and a hollow core region surrounded by the inner cladding region. The hollow tubes are not touching each other but are arranged with distance to adjacent hollow tubes. The hollow tubes each have an average outer diameter d2 and an average inner diameter d1, wherein d1/d2 is equal to or larger than about 0.8, such as equal to or larger than about 0.85, such as equal to or larger than about 0.9. Also, a laser system.

A method of making an optical fibre preform comprising providing a hollow outer tube of glass, providing a hollow primary capillary tube of glass with an outer diameter smaller than an inner diameter of the outer tube, positioning the primary capillary tube inside the outer tube such that an outer surface of the primary capillary tube lies against an inner surface of the outer tube along a contact line parallel to the longitudinal axes of the primary capillary tube and the outer tube, and bonding the primary capillary tube into its position inside the outer tube by directing a laser beam onto a surface of the outer tube or the primary capillary at one or more locations aligned with the contact line.

An optical fiber, manufacturing intermediate for forming an optical fiber and a method for forming an optical fiber. The method includes providing a manufacturing intermediate having an elongate body and having an aperture extending through the elongate body along an axial dimension of the elongate body, a boundary of the aperture defining an internal surface of the manufacturing intermediate. The method further includes etching the internal surface of the manufacturing intermediate using an etching substance, and drawing the manufacturing intermediate along the axial dimension so as to form the optical fiber.

Air core optical fiber structures in which the cladding is composed of an engineered optical metamaterial having a refractive index less than unity for at least one specific wavelength band and provides for total internal reflection of optical energy between the air core and metamaterial cladding. According to certain examples, a method of guiding optical energy includes constructing a hollow core optical fiber with an all-dielectric optical metamaterial cladding, coupling optical energy into the optical fiber having an operating wavelength near a resonance of the metamaterial cladding, and guiding the optical energy within the hollow core optical fiber by total internal reflection.

A method of drawing a material into sheet form includes forming a preform comprising at least one material as a large aspect ratio block wherein a first transverse dimension of the preform is much greater than a second transverse dimension substantially perpendicular to the first transverse dimension. A furnace having substantially linearly opposed heating elements one spaced from the other is provided and the heating elements are energized to apply heat to the preform to create a negative thermal gradient from an exterior surface along the first transverse dimension of the preform inward toward a central plane of the preform. The preform is drawn in such a manner that the material substantially maintains its first transverse dimension and deforms across its second transverse dimension.

A method of producing a microstructured optical fiber is disclosed. The method includes providing a preform and drawing the preform. The preform has a center axis, a length and a first end and a second end and has at least one longitudinal hole extending lengthwise. The method includes inserting a first end of a pressure tube into the hole of the preform at the first end of the preform and subjecting the hole of the preform to a controlled pressure via the pressure tube during the drawing.