Broadband light source device and method of creating broadband light pulses

Patent metadata

Field	Value
Publication number	US-10693271-B2
Application number	US-201716471035-A
Country	US
Kind code	B2
Filing date	Jan 9, 2017
Priority date	Jan 9, 2017
Publication date	Jun 23, 2020
Grant date	Jun 23, 2020

Abstract

A broadband light source device ( 100 ) for creating broadband light pulses ( 1 ) comprises a hollow-core fiber ( 10 ) of non-bandgap type including a filling gas and being arranged for creating the broadband light pulses ( 1 ) by an optical nonlinear broadening of pump laser pulses ( 2 ), wherein the hollow-core fiber ( 10 ) has an axial hollow light guiding fiber core ( 11 ), which supports core modes of a guided light field, and an inner fiber structure ( 12 ), which surrounds the fiber core ( 11 ) and which supports transverse wall modes of the guided light field, and a pump laser source device ( 20 ) being arranged for creating and providing the pump laser pulses ( 2 ) at an input side ( 13 ) of the hollow-core fiber ( 10 ), wherein the transverse wall modes include a fundamental transverse wall mode and second and higher order transverse wall modes, the broadband light pulses ( 1 ) have a core mode spectrum being determined by a fiber length, a fiber core diameter, at least one pump pulse and/or beam parameter of the pump laser pulses ( 2 ) and at least one gas parameter of the filling gas, and the inner fiber structure ( 12 ) of the hollow-core fiber ( 10 ) is configured such that at least the second and higher order transverse wall modes and the core mode spectrum have a spectral displacement relative to each other. Furthermore, a method of creating broadband light pulses is described.

First claim

The invention claimed is:

1. A broadband light source device configured for creating broadband light pulses, comprising:
a hollow-core fiber of non-bandgap type including a filling gas and being arranged to create the broadband light pulses by an optical non-linear broadening of pump laser pulses, wherein the hollow-core fiber has an axial hollow light guiding fiber core that supports core modes of a guided light field and an inner fiber structure that surrounds the fiber core and that supports transverse wall modes of the guided light field, and
a pump laser source device being arranged to create and provide the pump laser pulses at an input side of the hollow-core fiber, wherein transverse wall modes include a fundamental transverse wall mode and second and higher order transverse wall modes, and
wherein the broadband light pulses have a core mode spectrum being determined by a fiber length, a fiber core diameter, at least one pump pulse and/or beam parameter of the pump laser pulses and at least one gas parameter of the filling gas,
wherein the inner fiber structure of the hollow-core fiber is configured such that at least the second and higher order transverse wall modes and the core mode spectrum have a spectral displacement relative to each other.

2. The broadband light source device of claim 1 , wherein the inner fiber structure of the hollow-core fiber is configured such that all transverse wall modes and the core mode spectrum have a spectral displacement relative to each other.

3. The broadband light source device of claim 1 , wherein fiber walls of the inner fiber structure facing to the fiber core have a wall thickness being selected such that at least the second and higher order transverse wall modes are spectrally shifted to shorter wavelengths relative to the core mode spectrum.

4. The broadband light source device of claim 3 , wherein the fiber walls of the inner fiber structure have the selected limit wall thickness exclusively in a longitudinal section of the hollow-core fiber where the UV light pulses are created and transmitted through the hollow-core fiber.

5. The broadband light source device of claim 3 , wherein:
the inner fiber structure comprises a single ring or a Kagomé structure, and
the fiber walls facing to the fiber core have a wall thickness (t) being selected such that

t
<

λ
min

2
⁢

n
2
2

-

n
1
2

wherein λ min a shortest wavelength of the core mode spectrum, n 1 is a refractive index of the filling gas in the hollow-core fiber and n 2 is a refractive index of the inner fiber structure.

6. The broadband light source device of claim 5 , wherein:
the wall thickness is in a range from 70 nm to 300 nm or from 70 nm to 150 nm, and/or
the shortest wavelength λ min of the core mode spectrum is in a range from 170 nm to 250 nm.

7. The broadband light source device of claim 1 , further comprising:
an adjustment device being arranged to adjust at least one of at least one pump pulse parameter, such as pulse duration, pulse energy, pulse shape and/or pulse spectrum, and at least one beam parameter, in particular modal shape, pointing and/or stability.

8. The broadband light source device of claim 7 , further comprising:
a gas supply device being connected with the hollow-core fiber and being arranged to supply the filling gas to the hollow-core fiber,
wherein the adjustment device is connected with the gas supply device for adjusting the at least one gas parameter of the filling gas.

9. The broadband light source device of claim 1 , further comprising:
a monitoring device being arranged to monitor at least a part of the core mode spectrum of the UV light pulses output from the hollow core fiber.

10. The broadband light source device of claim 9 , further comprising:
a control loop including the monitoring device and the adjustment device,
wherein the control loop is adapted to control the adjustment device such that the spectral displacement of the transverse wall modes and the core mode spectrum is kept during operation of the UV light source device.

11. A method of creating broadband light pulses, comprising:
coupling pump laser pulses into a hollow-core fiber of non-bandgap type including a filling gas, wherein the hollow-core fiber has an axial hollow light guiding fiber core that supports core modes of a guided light field and an inner fiber structure that surrounds the fiber core and that supports transverse wall modes of the guided light field, wherein the transverse wall modes include a fundamental transverse wall mode and second and higher order transverse wall modes;
creating the broadband light pulses by an optical non-linear broadening of the pump laser pulses in the hollow-core fiber, the broadband light pulses having a core mode spectrum being determined by a fiber length, a fiber core diameter, at least one pump pulse and/or beam parameter of the pump laser pulses and at least one gas parameter of the filling gas; and
spectrally displacing at least the second and higher order transverse wall modes and the core mode spectrum relative to each other.

12. The method of claim 11 , wherein all transverse wall modes and the core mode spectrum are spectrally displaced relative to each other.

13. The method of claim 11 , wherein the fiber walls of the inner fiber structure facing to the fiber core have a wall thickness selected such that at least the second and higher order transverse wall modes are spectrally shifted to shorter wavelengths relative to the core mode spectrum.

14. The method of claim 13 , wherein the fiber walls of the inner fiber structure have the selected limit wall thickness exclusively in a longitudinal section of the hollow-core fiber where the broadband light pulses are created and transmitted through the hollow-core fiber.

15. The method of claim 11 , wherein the inner fiber structure comprises a single ring or a Kagomé structure, and the fiber walls facing to the fiber core have a wall thickness being selected such that

t
<

λ
min

2
⁢

n
2
2

-

n
1
2

wherein λ min is the shortest wavelength of the core mode spectrum, n 1 is a refractive index of the filling gas in the hollow-core fiber and n 2 is a refractive index of the inner fiber structure.

16. The method of claim 15 , wherein:
the wall thickness is in a

Assignees

• Max Planck Gesellschaft
• Max Plank Gesellschaft Zur Foerderung Der Wss E V

Inventors

• Uebel Patrick Sebastian
• Russell Philip St J
• Bauerschmidt Sebastian Thomas

Classifications

• H01S3/1305

  Feedback control systems · CPC title

• H01S3/0407

  Liquid cooling, e.g. by water · CPC title

• G02F1/355

  characterised by the materials used · CPC title

• G02F1/353 Primary

  Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams · CPC title

• G02F1/3501

  Constructional details or arrangements of non-linear optical devices, e.g. shape of non-linear crystals · CPC title