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 fiber (100) of non-bandgap type comprises a hollow core region (10) axially extending along the hollow-core fiber (100) and having a smallest transverse core dimension (D), wherein the core region (10) is adapted for guiding a transverse fundamental core mode and transverse higher order core modes, and an inner cladding region (20) comprising an arrangement of anti-resonant elements (AREs) (21, 21A, 21B) surrounding the core region (10) along the hollow-core fiber (100), each having a smallest transverse ARE dimension (d.sub.i) and being adapted for guiding transverse ARE modes, wherein the core region (10) and the AREs (21, 21A, 21B) are configured to provide phase matching of the higher order core modes and the ARE modes and the ARE dimension (d.sub.i) and the core dimension (D) are selected such that a ratio of the ARE and core dimensions (d.sub.i/D) is approximated to a quotient of zeros of Bessel functions of first kind (u.sub.lm,ARE/u.sub.lm,core), multiplied with a fitting factor in a range of 0.9 to 1.5, with m being the m-th zero of the Bessel function of first kind of order 1, said zeros of the Bessel functions describing the LP.sub.lm ARE modes and LP.sub.lm higher order core modes, respectively. Furthermore, an optical device (200) including the hollow-core fiber (100) and a method of manufacturing the hollow-core fiber are described.

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.

This application relates generally to an optical fiber for the delivery of infrared light where the polarization state of the light entering the fiber is preserved upon exiting the fiber and the related methods for making thereof. The optical fiber has a wavelength between about 0.9 ?m and 15 ?m, comprises at least one infrared-transmitting glass, and has a polarization-maintaining (PM) transverse cross-sectional structure. The infrared-transmitting, polarization-maintaining (IR-PM) optical fiber has a birefringence greater than 10.sup.?5 and has applications in dual-use technologies including laser power delivery, sensing and imaging.

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.