Hollow-core photonic crystal fiber and method of manufacturing thereof

A hollow-core photonic crystal fiber (HC-PCF), being configured for guiding at least one mode of a light field along a mode guiding section of the HC-PCF, comprising:

• an outer jacket, an inner cladding, and a hollow core, that extend along the HC-PCF, wherein:
• the inner cladding is arranged on an interior surface of the outer jacket and comprises anti-resonant structures surrounding the hollow core, and
• the hollow core has a mode guiding core diameter (d) provided along the mode guiding section of the HC-PCF,
• wherein at least one fiber end of the HC-PCF has a light field coupling section in which the hollow core is tapered over an axial coupling section length from a fiber end core diameter (D) at the at least one fiber end to the mode guiding core diameter (d), and
• wherein an axial transition length over which the fiber core diameter dimension reduces in the light field coupling section from the fiber end core diameter (D) to (0.5*(D+d)) is at least 0.5 times the mode guiding core diameter (d) and/or at most 0.5 times a transition dimension (π(D2d2−d4)0.5/(4λ)), where λ is the central wavelength of the light field.

A hollow-core photonic crystal fiber (HC-PCF), being configured for guiding at least one mode of a light field along a mode guiding section of the HC-PCF, comprising:

• an outer jacket, an inner cladding, and a hollow core, that extend along the HC-PCF, wherein:
• the inner cladding is arranged on an interior surface of the outer jacket and comprises anti-resonant structures surrounding the hollow core, and
• the hollow core has a mode guiding core diameter (d) provided along the mode guiding section of the HC-PCF,
• wherein at least one fiber end of the HC-PCF has a light field coupling section in which the hollow core is tapered over an axial coupling section length from a fiber end core diameter (D) at the at least one fiber end to the mode guiding core diameter (d), and
• wherein the inner cladding does not extend to an opening of the at least one fiber end.