Hollow-core photonic crystal fiber and method of manufacturing thereof
A hollow-core photonic crystal fiber (HC-PCF) ( 10 ) for guiding at least one mode of a light field ( 1 ) along a mode guiding section ( 11 ) of the HC-PCF ( 10 ), comprises an outer jacket ( 12 ), an inner cladding ( 13 ) and a hollow core ( 14 ), which extend along the HC-PCF ( 10 ), wherein the inner cladding ( 13 ) is arranged on an interior surface of the outer jacket ( 12 ) and comprises anti-resonant structures ( 15 ) surrounding the hollow core ( 14 ), and the hollow core ( 14 ) has a mode guiding core diameter (d) provided along the mode guiding section of the HC-PCF ( 10 ), and wherein at least one fiber end ( 16 ) of the HC-PCF ( 10 ) has a light field coupling section ( 17 ) in which the hollow core ( 14 ) is tapered over an axial coupling section length from a fiber end core diameter (D) at the at least one fiber end ( 16 ) to the mode guiding core diameter (d). Furthermore, methods of using the HC-PCF and manufacturing the HC-PCF are described.
1. 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 the axial coupling section length is less than about 1 mm, and
wherein the inner cladding thickness decreases towards an opening of the at least one fiber end.
2. The hollow-core photonic crystal fiber of claim 1 , wherein:
the anti-resonant structures have a cross-sectional dimension that gradually increases in the light field coupling section towards the mode guiding section.
3. The hollow-core photonic crystal fiber of claim 1 , wherein:
the anti-resonant structures have rounded ends facing toward the at least one fiber end.
4. The hollow-core photonic crystal fiber of claim 1 , wherein:
the inner cladding extends to the opening of the at least one fiber end.
5. The hollow-core photonic crystal fiber of claim 1 , wherein:
the light field coupling section is provided at an incoupling end of the HC-PCF only.
6. The hollow-core photonic crystal fiber of claim 1 , wherein:
the HC-PCF is configured to subject a light field to an optically non-linear process, in particular spectral broadening, or
the HC-PCF is configured to deliver a light field to an application site.
7. The hollow-core photonic crystal fiber of claim 1 , wherein the light field coupling section is formed by thermal treatment of the HC-PCF.
8. The hollow-core photonic crystal fiber of claim 7 , wherein
the anti-resonant structures of the inner cladding are softened and the light field coupling section is formed by the effect of surface tension in the softened anti-resonant structures.
9. The hollow-core photonic crystal fiber of claim 8 , wherein:
the thermal treatment comprises a heating of the HC-PCF such that the anti-resonant structures of the inner cladding are softened and the light field coupling section is formed by the combined effect of surface tension in the softened anti-resonant structures and an applied vacuum in at least one of the anti-resonant structures.
10. The hollow-core photonic crystal fiber of claim 8 , wherein:
the thermal treatment comprises a heating of the HC-PCF such that the anti-resonant structures of the inner cladding are softened and the light field coupling section is formed by the combined effect of surface tension in the softened anti-resonant structures and an applied pressure in the mode guiding core.
11. A method of manufacturing a hollow-core photonic crystal fiber (HC-PCF), comprising:
forming the HC-PCF with 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; and
forming a light field coupling section by thermal treatment of the HC-PCF 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 the axial coupling section length being formed less than about 1 mm, and
wherein the inner cladding is formed to a thickness that decreases towards an opening of the at least one fiber end.
12. The method according to claim 11 , further comprising:
subjecting at least one fiber section of the HC-PCF to the thermal treatment, and
cutting the HC-PCF in the at least one thermally treated fiber section and with a distance thereof to a predetermined fiber length for forming the light field coupling section at the at least one fiber end.
13. The method according to claim 11 , further comprising:
cutting the HC-PCF to a predetermined fiber length to be obtained, and
subjecting at least one fiber end of the cut HC-PCF to the thermal treatment for forming the light field coupling section at the at least one fiber end.
14. The method according to claim 12 , wherein the thermal treatment comprises a heating of the HC-PCF such that the anti-resonant structures of the inner cladding are softened and the light field coupling section is formed by the effect of surface tension in the softened anti-resonant structures.
15. The method according to claim 13 , wherein the thermal treatment comprises a heating of the HC-PCF such that the anti-resonant structures of the inner cladding are softened and the light field coupling section is formed by the effect of surface tension in the softened anti-resonant structures.
16. The method according to claim 12 , wherein the thermal treatment comprises a heating of the HC-PCF such that the anti-resonant structures of the inner cladding are softened and the light field coupling section is formed by the combined effect of surface tension in the softened anti-resonant structures and an applied vacuum in at least one of the anti-resonant structures.
17. The method according to claim 13 , wherein the thermal treatment comprises a heating of the HC-PCF such that the anti-resonant structures of the inner cladding are softened and the light field coupling section is formed by the combined effect of surface tension in the softened anti-resonant structures and an applied vacuum in at least one of the anti-resonant structures.
18. The method according to claim 12 , wherein the thermal treatment comprises a heating of the HC-PCF such that the anti-resonant structures of the inner cladding are softened and the light field coupling section is formed by the combined effect of surface tension in the softened anti-resonant structures and an applied pressure in the mode guiding core.
19. The method according to claim 13 , wherein the thermal treatment comprises a heating of the HC-PCF such that the anti-resonant structures of the inner cladding are softened and the light field coupling section is formed by the combined effect of surface tension in the softened anti-resonant structures and an applied pressure in the mode guiding core.