Hollow-core photonic crystal fiber based optical component for broadband radiation generation

1. An optical component, being configured to function as an optical frequency converter in a broadband radiation source device, comprising:

a gas cell; and

a hollow-core photonic crystal fiber at least partially enclosed within the gas cell,

wherein the gas cell comprises filling elements configured to reduce a local cavity volume of the optical component, and

wherein the filling elements are arranged symmetrically about an optical axis of the hollow-core photonic crystal fiber.

2. The optical component of claim 1 , wherein the hollow-core photonic crystal fiber is wholly enclosed within the gas cell.

3. The optical component of claim 1 , wherein the gas cell comprises a plurality of sub-cells, the plurality of sub-cells comprising two end sub-cells, enclosing respective ends of the hollow-core photonic crystal fiber.

4. The optical component of claim 3 , wherein the plurality of sub-cells extend along a full length of the hollow-core photonic crystal fiber and further comprises a central sub-cell.

5. The optical component of claim 4 , wherein an external cross-section diameter of the central sub-cell is smaller than an external cross-section diameter of the two end sub-cells.

6. The optical component of claim 4 , wherein the central sub-cell comprises a pressure pipe.

7. The optical component of claim 1 , wherein a maximum value of the local cavity volume is one of: 32 cm 3 per cm of length of the hollow-core photonic crystal fiber, 28 cm 3 per cm of length of the hollow-core photonic crystal fiber, 24 cm 3 per cm of length of the hollow-core photonic crystal fiber, 20 cm 3 per cm of length of the hollow-core photonic crystal fiber, 16 cm 3 per cm of length of the hollow-core photonic crystal fiber, 12 cm 3 per cm of length of the hollow-core photonic crystal fiber, 8 cm 3 per cm of length of the hollow-core photonic crystal fiber, or 4 cm 3 per cm of length of the hollow-core photonic crystal fiber.

8. The optical component of claim 1 , wherein the hollow-core photonic crystal fiber comprises one or more of: a hollow-core anti-resonant reflecting fiber, an inhibited coupling hollow-core photonic crystal fiber, a hollow core revolver fiber, and a nested anti-resonant reflecting fiber.

9. The optical component of claim 1 , comprising an input optical window for admitting a pump laser pulse and an output optical window for outputting a broadband radiation, wherein the input optical window and the output optical window are located at respective ends of the gas cell.

10. The optical component of claim 1 , wherein the local cavity volume is defined for at least 70%, 80%, 90%, 95%, or 98% of a length of the hollow-core photonic crystal fiber that is enclosed within the gas cell.

11. The optical component of claim 1 , wherein the filling elements comprise a solid material.

12. The optical component of claim 11 , wherein the solid material comprises a metal.

13. The optical component of claim 1 , wherein the filling elements extend along a length of the gas cell.

14. The optical component of claim 1 , wherein the filling elements extend along a circumference of the gas cell.

15. The optical component of claim 1 , wherein the filling elements comprise a rectangular cross-section, a square cross-section, a rounded rectangular cross-section, a rounded square cross-section, an elliptical cross-section, a circular cross-section, or an annular cross-section.

16. A broadband light source device comprising the optical component of claim 1 , and being configured for creating broadband radiation.

17. The broadband light source device of claim 16 , further comprising a pump laser being operable to generate ultrashort pump laser pulses, the optical component being operable to convert the ultrashort pump laser pulses into the broadband radiation.

18. A metrology device comprising the broadband light source device of claim 17 .

19. The metrology device of claim 18 comprising a scatterometer metrology apparatus, a level sensor, or an alignment sensor.

20. An optical component, being configured to function as an optical frequency converter in a broadband radiation source device, comprising:

a gas cell; and

a hollow-core photonic crystal fiber at least partially enclosed within the gas cell,

wherein the gas cell comprises filling elements configured to reduce a local cavity volume of the optical component,

wherein the filling elements extend along a circumference of the gas cell and are separated by a plurality of gaps, and

wherein the filling elements extend along at least 70% of a length of the gas cell.