An optical fiber, an apparatus for receiving input radiation and broadening a frequency range, a radiation source, a metrology arrangement and a lithographic apparatus are provided. The optical fiber comprises a hollow core, a cladding portion and a support portion. The cladding portion surrounds the hollow core and comprises a plurality of anti-resonance elements for guiding radiation through the hollow core. The support portion surrounds and supports the cladding portion and comprises an inner support portion, an outer support portion and a deformable connecting portion that connects the inner support portion to the outer support portion.

The selection of starting materials used in the process of forming an MCR is controlled to specifically define the physical properties of the core tube and/or the capillary tubes in the local vicinity of the core tube. The physical properties are considered to include, but are not limited to, the diameter of a given tube/capillary, its wall thickness, and its geometry (e.g., circular, non-circular). A goal is to select starting materials with physical properties that yield a final hollow core optical fiber with a uniform core region (for the purposes of the present invention, a uniform core region is one where the struts of cladding periodic array surrounding the central core are uniform in length and thickness (with the nodes between the struts thus being uniformly spaced apart), which yields a core wall of essentially uniform thickness and circularity.

A preform (10) for an antiresonant hollow core optical fibre comprises an outer jacket tube (12) having an inner surface and a central longitudinal axis (24); a plurality of antiresonant cladding tubes (14) spaced apart at predefined peripheral locations around the inner surface of the outer jacket tube (12), each antiresonant cladding tube (14) in contact with the inner surface such that a central longitudinal axis (26) of each antiresonant cladding tube (14) is at a first radial distance from the central longitudinal axis (24) of the outer jacket tube (12); and a plurality of spacing elements (22) disposed alternately with the antiresonant cladding tubes (14) and each in contact with an outer surface of each of two adjacent antiresonant cladding tubes (14) at one or more contact points (28), the contact points (28) at a second radial distance from the central longitudinal axis (24) of the outer jacket tube (12), the second radial distance being greater than the first radial distance.

An optical fibre for an ultrafast laser endoscope including at least the following structures: a hollow core, the periphery of which has an order of symmetry of at least six when considering axes of symmetry passing through the centre of the core and through the centre of convex shapes, seen from the centre of the core, the convex shapes at least partly making up the periphery of the core; an intermediate layer of cellular structure surrounding the core; a lightconducting peripheral structure surrounding the intermediate layer of cellular structure; and an outer sheath surrounding the light-conducting peripheral structure. A particular advantage of the optical fibre is that it optimizes the emission of a high-power flux associated with fluorescence collection.

The present invention provides a method for manufacturing an optical fiber base material and an optical fiber base material, the method including: arranging a rod containing SiO.sub.2 family glass for core, in a container; pouring a SiO.sub.2 glass raw material solution for cladding layer and a hardener into the container, the glass raw material solution containing a hardening resin; solidifying the glass raw material solution through a self-hardening reaction; and then drying the solidified material and heating the solidified material in chlorine gas, to manufacture an optical fiber base material in which a SiO.sub.2 cladding layer is formed in an outer periphery of the rod containing SiO.sub.2 family glass for core.

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.

According to embodiments of the present invention, a fiber preform or an optical fiber is provided. The fiber preform or the optical fiber includes a core region, and a cladding arrangement comprising a first cladding region comprising a plurality of rods entirely surrounding the core region, and a second cladding region in between the core region and the first cladding region, the second cladding region comprising a plurality of tubes, wherein a plurality of splits are defined in the second cladding region. According to further embodiments of the present invention, a method for forming a fiber preform and a method for forming an optical fiber are also provided.

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 process of fabricating the microstructure core rod preform used in the fabrication of a hollow core optical fiber includes the step of applying external pressure to selected hollow regions during the drawing of the preform from the initial assembly of capillary tubes. The application of pressure assists the selected hollow regions in maintaining their shape as much as possible during draw, and reduces distortions in the microstructure cells in close proximity to the core by controlling glass distribution during MCR draw.

A Photonic Crystal Fiber (PCF) a method of its production and a supercontinuum light source comprising such PCF. The PCF has a longitudinal axis and includes a core extending along the length of said longitudinal axis and a cladding region surrounding the core. At least the cladding region includes a plurality of microstructures in the form of inclusions extending along the longitudinal axis of the PCF in at least a microstructured length section. In at least a degradation resistant length section of the microstructured length section the PCF includes hydrogen and/or deuterium. In at least the degradation resistant length section the PCF further includes a main coating surrounding the cladding region, which main coating is hermetic for the hydrogen and/or deuterium at a temperature below T.sub.h, wherein T.sub.h is at least about 50 C., preferably 50 C.<T.sub.h<250 C.