A method of forming a glass preform of predetermined length comprises providing a length of glass material to be separated to form a preform length and a remaining length; forming a notch in the glass material; inducing a tensile stress in excess of the tensile strength of the glass in an area adjacent to the notch; and separating the preform length from the remaining length at the notch.

An apparatus (100) for making glass tubing (200) of a desired non-circular cross-sectional profile (cf FIG. 3) includes a mandrel (101) adapted for positioning proximate heat-softened tubing. The mandrel (101) has a nose (102) and a nozzle section (120) with a chosen profile that will define a final cross-sectional profile of the tubing. The nozzle section (120) has a feed chamber (140) for receiving a gas from a source (207) and a porous and/or foraminous circumferential surface (132,134) through which the gas can be discharged to an exterior of the mandrel. The gas discharges to the exterior of the mandrel, forming a film of pressurized gas in the gap (314, 318) between the porous circumferential surface (132,134) and the heat-softened tubing (200). A method of forming tubing having a non-circular cross-sectional profile using the apparatus is also provided. A glass sleeve made from the reshaped or formed tubing is also disclosed: a monolithic sleeve made of parallel, opposite, flat and smooth front and back covers for use in an electronic device (cf FIG. 13). Some glass-ceramic materials may also be suitable for the tubing, such as transparent beta spodumene.

An apparatus (100) for making glass tubing (200) of a desired non-circular cross-sectional profile (cf FIG. 3) includes a mandrel (101) adapted for positioning proximate heat-softened tubing. The mandrel (101) has a nose (102) and a nozzle section (120) with a chosen profile that will define a final cross-sectional profile of the tubing. The nozzle section (120) has a feed chamber (140) for receiving a gas from a source (207) and a porous and/or foraminous circumferential surface (132,134) through which the gas can be discharged to an exterior of the mandrel. The gas discharges to the exterior of the mandrel, forming a film of pressurized gas in the gap (314, 318) between the porous circumferential surface (132,134) and the heat-softened tubing (200). A method of forming tubing having a non-circular cross-sectional profile using the apparatus is also provided. A glass sleeve made from the reshaped or formed tubing is also disclosed: a monolithic sleeve made of parallel, opposite, flat and smooth front and back covers for use in an electronic device (cf FIG. 13). Some glass-ceramic materials may also be suitable for the tubing, such as transparent beta spodumene.

A method for processing a workpiece using a pulsed laser beam includes beam shaping of the laser beam to form an elongated focus zone in the material of the workpiece. The beam shaping is carried out by using an arrangement of diffractive, reflective and/or refractive optical assemblies. The beam shaping includes focus-forming beam shaping to cause beam portions to enter at an entry angle to a beam axis of the laser beam for forming the elongated focus zone along the beam axis in the workpiece by way of interference, and phase-correcting beam shaping to counteract any influence of the interference by entrance of the laser beam into the workpiece. The method further includes setting beam parameters of the laser beam so that the material of the workpiece is modified in the elongated focus zone.

An apparatus for the continuous production of hollow quartz-glass ingots, comprising a) a crucible or refractory tank for providing a softened quartz-glass mass having a dieorifice in the bottom of the crucible or refractory tank; b) a mandrel vertically drawing off the softened quartz-glass mass through a die toprovide a hollow quartz-glass ingot; and c) a cutting section for on-line cutting of the hollow quartz-glass ingot to a specificlength, characterized in that the apparatus comprises active means for cooling the internalsurface of the hollow quartz-glass ingot prior to the cutting station.

Embodiments of the present method of laser cutting a laser wavelength transparent glass article comprises feeding at least one glass article to a pulsed laser assembly having at least one pulsed laser, wherein the pulsed laser defines a laser beam focal line with a length of 0.1-100 mm, the glass article being comprised of two end sections, and at least one lateral surface disposed lengthwise between the end sections. The method further comprises laser cutting at least one perforation line onto the lateral surface of the glass article while there is relative motion between the glass article and the pulsed laser and separating the glass article along the at least one perforation line to yield a laser cut glass article.

Embodiments of the present method of laser cutting a laser wavelength transparent glass article comprises feeding at least one glass article to a pulsed laser assembly having at least one pulsed laser, wherein the pulsed laser defines a laser beam focal line with a length of 0.1-100 mm, the glass article being comprised of two end sections, and at least one lateral surface disposed lengthwise between the end sections. The method further comprises laser cutting at least one perforation line onto the lateral surface of the glass article while there is relative motion between the glass article and the pulsed laser and separating the glass article along the at least one perforation line to yield a laser cut glass article.

Laser waveguides, methods and systems for forming a laser waveguide are provided. The waveguide includes an inner cladding layer surrounding a central axis and a glass core surrounding and located outside of the inner cladding layer. The glass core includes a laser-active material. The waveguide includes an outer cladding layer surrounding and located outside of the glass core. The inner cladding, outer cladding and/or core may surround a hollow central channel or bore and may be annular in shape.

At least one glass tube has an azimuthal wall thickness deviation WTD of not more than 6.0%, the azimuthal wall thickness deviation being determined based on a lowest wall thickness value and a highest wall thickness value measured within a cross-section of the at least one glass tube, the azimuthal wall thickness deviation WTD being calculated according to the following formula:

[00001]$WTD=100-\left(\frac{\mathrm{lowest}\mathrm{wall}\mathrm{thickness}\mathrm{value}}{\mathrm{highest}\mathrm{wall}\mathrm{thickness}\mathrm{value}}*100\right)\%.$

At least one glass tube has an azimuthal wall thickness deviation WTD of not more than 6.0%, the azimuthal wall thickness deviation being determined based on a lowest wall thickness value and a highest wall thickness value measured within a cross-section of the at least one glass tube, the azimuthal wall thickness deviation WTD being calculated according to the following formula:

[00001]$WTD=100-\left(\frac{\mathrm{lowest}\mathrm{wall}\mathrm{thickness}\mathrm{value}}{\mathrm{highest}\mathrm{wall}\mathrm{thickness}\mathrm{value}}*100\right)\%.$