Microstructured optical fiber, supercontinuum light source comprising microstructured optical fiber and use of such light source

Patent metadata

Field	Value
Publication number	US-2016156148-A1
Application number	US-201414903772-A
Country	US
Kind code	A1
Filing date	Jul 7, 2014
Priority date	Jul 10, 2013
Publication date	Jun 2, 2016
Grant date	—

Abstract

The invention relates to a microstructured optical fiber for generating supercontinuum light. The optical fiber comprises a core and a cladding region surrounding the core. The optical fiber comprises a first fiber length section, a second fiber length section as well as an intermediate fiber length section between said first and second fiber length sections. The first fiber length section has a core with a first characteristic core diameter larger than about 7 μm. The second fiber length section has a core with a second characteristic core diameter, smaller than said first characteristic core diameter. The intermediate length section of the optical fiber comprises a core which is tapered from said first characteristic core diameter to said second characteristic core diameter over a tapered length. The invention also relates to a supercontinuum light source comprising an optical fiber according to the invention and a pump light source.

First claim

1 - 43 . (canceled)

44 . A microstructured optical fiber for generating supercontinuum light upon feeding of light having a first wavelength λ 1 , the optical fiber having a length and a longitudinal axis along its length and comprising a core region for guiding light along the length of said optical fiber, and a first cladding region surrounding said core region, wherein:
said optical fiber, along its length, comprises a first fiber length section, a second fiber length section as well as an intermediate fiber length section between said first and second fiber length sections,
said first fiber length section has a core region with a first characteristic core diameter W 1 in a cross-section through the microstructured optical fiber perpendicularly to the longitudinal axis, wherein said first characteristic core diameter is larger than about 7 μm,
said second fiber length section has a core region with a second characteristic core diameter W 2 in a cross-section through the microstructured optical fiber perpendicularly to the longitudinal axis, where said second characteristic core diameter W 2 is smaller than said first characteristic core diameter W 1 ,
said intermediate length section of the optical fiber comprises a core region which is tapered from said first characteristic core diameter W 1 to said second characteristic core diameter W 2 over a tapered length L i ,
said first fiber length section has normal dispersion at said first wavelength λ 1 and said second fiber length section has zero dispersion at a second wavelength ZDW 2 , where ZDW 2 is up to about λ 1 +50 nm and said second fiber length section has anomalous dispersion at wavelengths above said second wavelength ZDW 2 .

45 . The optical fiber according to claim 44 , wherein said first wavelength λ 1 is up to about 1100 nm.

46 . The optical fiber according to claim 44 , wherein the first fiber length section has zero dispersion at a wavelength ZDW 1 where ZDW 1 >about λ 1 +20 nm.

47 . The optical fiber according to claim 44 , wherein said first characteristic core diameter is larger than about 1.5 times the second characteristic core diameter.

48 . The optical fiber according to claim 44 , wherein said first characteristic core diameter is larger than about 10 μm.

49 . The optical fiber according to claim 44 , wherein said second characteristic core diameter is larger than about 4 μm.

50 . The optical fiber according to claim 44 , wherein said inner cladding comprises a microstructure, said microstructure comprising a plurality of microstructure elements having a microstructure element diameter, d f , said microstructure elements being arranged at a pitch ´, said pitch ´ being a measure of a spacing between the microstructure elements, wherein said microstructure is at least partially maintained along the first and second fiber length sections of the optical fiber.

51 . The optical fiber according to claim 50 , wherein the relative size (d f / ) of the microstructure elements is larger in the second fiber length section of the optical fiber than in the first fiber length section of the optical fiber, said relative size being the ratio between the diameter (d f ) of the microstructure elements and the pitch .

52 . The optical fiber according to claim 50 , wherein the relative size (d f / ) of the microstructure elements is chosen so that the first fiber length section is a single mode fiber at least at the first wavelength λ 1 .

53 . The optical fiber according to claim 44 , wherein said optical fiber further comprising a second cladding surrounding said first cladding, wherein:
i) said core region is adapted to guide an optical signal at said first wavelength λ 1 , said core region having an effective refractive index n core , and where said core region comprises a material doped with at least one rare earth element, ii) said first cladding being arranged for guiding light at a third wavelength λ 3 , said first cladding having an effective refractive index n first-clad , and iii) said second cladding having an effective refractive index n second-clad wherein n core >n first-clad >n second-clad and λ 1 >λ 3 .

54 . A supercontinuum light source comprising:
i. a microstructured optical fiber for generating supercontinuum light at a wavelength λ 1 , said microstructured optical fiber comprising a core region that is capable of guiding light along a longitudinal axis of said optical fiber, and a first cladding region surrounding said core region, ii. a pump light source arranged to feed light into said core region at an input end of said optical fiber, said light having, a first wavelength, λ 1 ; wherein: said optical fiber has a length and a longitudinal axis along its length, wherein said optical fiber comprises a first fiber length section, a second fiber length section as well as an intermediate fiber length section between the first and second fiber length sections, said first fiber length section has a core region with a first characteristic core diameter W 1 , wherein said first characteristic core diameter is larger than about 7 μm, said second fiber length section has a core region with a second characteristic core diameter W 2 in a cross-section through the microstructured optical fiber perpendicularly to the longitudinal axis, where said second characteristic core diameter W 2 is smaller than said first characteristic core diameter W 1 , said intermediate fiber length section of the optical fiber comprises a core region which is tapered from said first characteristic core diameter W 1 to said second characteristic core diameter W 2 over a tapered length L i . said first fiber length section has normal dispersion at a first wavelength λ 1 and said second fiber length section has zero dispersion at a second wavelength ZDW 2 , where ZDW 2 is up to about λ 1 +50 nm, and said second fiber length section has anomalous dispersion at wavelengths above said second wavelength ZDW 2 .

55 . The supercontinuum light source according to claim 54 , wherein said first characteristic core diameter is larger than about 1.5 times the second characteristic core.

56 . The supercontinuum light source according to claim 54 , wherein said first characteristic core diameter is larger than about 10 μm.

57 . The supercontinuum light source according to claim 54 , wherein the relative size (d f / ) of the microstructure elements is chosen so that the first fiber length section is a single mode fiber at least at the first wavelength λ 1 .

58 . The supercontinuum light source according to claim 54 , wherein the pulse duration Δt of the pump light source is more than about 50.

59 . The supercontinuum light source according to claim 54 , wherein the pulse duration Δt of the pump light source is less than about 50 ns.

60 . A supercontinuum light source according to claim 54 , wherein an output pulse from said light source has a pulse length of less than about 20 ns and an output spectral density over at least 50 nm between 400 nm and 900 nm of at least 500 nJ/10 nm.

61 . A supercontinuum light source according to claim 54 , said microstructured optical fiber further comprising a second cladding surrounding said first cladding, wherein:
i) said core region is adapted to guide an optical signal at said first wavelength λ 1 , said core region having an effective refractive index n core , and where said core region comprises a material doped with at least one rare earth element, ii) a second pump light source is arranged for feeding light at a second

Assignees

• Nkt Photonics As

Inventors

• Thomsen Carsten L
• Alkeskjold Thomas T
• Thomsen Erik B

Classifications

• G02B6/02338

  Structured core, e.g. core contains more than one material, non-constant refractive index distribution in core, asymmetric or non-circular elements in core unit, multiple cores, insertions between core and clad · CPC title

• G02F1/353

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

• H01S3/06741

  Photonic crystal fibre, i.e. the fibre having a photonic bandgap · CPC title

• G02B6/02214

  tailored to obtain the desired dispersion, e.g. dispersion shifted, dispersion flattened · CPC title

• G02B6/02333

  Core having higher refractive index than cladding, e.g. solid core, effective index guiding · CPC title