Microstructured fiber and supercontinuum light source

Abstract

A microstructured optical fiber including a core region and a cladding region which surrounds the core region. The cladding region includes a plurality of cladding features within a cladding background material, wherein the cladding region includes an inner cladding region with at least one inner ring of cladding features and an outer cladding region with outer cladding rings of outer cladding features. The inner cladding features have a first characteristic diameter and the outer cladding region includes a plurality of outer cladding features having a characteristic diameter smaller than the first characteristic diameter. The core region has a diameter of at least about 2 μm. A cascade optical fiber with at least one fiber as described, as well as a source of optical supercontinuum generation.

1 . (canceled) 
     
     
         2 . A source of optical supercontinuum generation,
 the source comprising a microstructured optical fiber and a pump laser source adapted to generate pump radiation at a pump wavelength and to launch said pump radiation into said microstructured optical fiber,   wherein the microstructured optical fiber has a length and a longitudinal axis along its length and comprising a core region and a cladding region surrounding the core region,   said cladding region comprising a cladding background material and a plurality of cladding features within the cladding background material, said cladding features being arranged around the core region,   wherein said cladding region in at least a length section of the fiber comprises an inner cladding region comprising at least two inner rings of cladding features, and an outer cladding region comprising at least one outer ring of outer cladding features, said inner cladding region being adjacent to the core region and said outer cladding region being adjacent to the inner cladding region,   wherein each ring of cladding features comprises bridges of cladding background material separating adjacent features of the ring,   wherein the bridges of at least one of the at least two inner rings has an average minimum width (w 1 ),   wherein the average minimum width (w 2 ) of the bridges of an outer ring is larger than the average minimum width (w 1 ),   said microstructured optical fiber being arranged to provide supercontinuum radiation including light at short wavelengths below 500 nm upon launch of said pump radiation into said microstructured optical fiber.   
     
     
         3 . The source of optical supercontinuum generation according to  claim 2 , wherein the core region is substantially circular. 
     
     
         4 . The source of optical supercontinuum generation according to  claim 2 , wherein the inner cladding region is adjacent to the core region and the outer cladding region is adjacent to the inner cladding region. 
     
     
         5 . The source of optical supercontinuum generation according to  claim 2 , wherein the average minimum width (w 1 ) is about 1.2 μm or less. 
     
     
         6 . The source of optical supercontinuum generation according to  claim 2 , wherein the average minimum width (w 1 ) is smaller than a Zero Dispersion Wavelength ZDW of the fundamental core mode. 
     
     
         7 . The source of optical supercontinuum generation according to  claim 2 , wherein the bridges of at least one of the inner rings has a substantially equal minimum width. 
     
     
         8 . The source of optical supercontinuum generation according to  claim 2 , wherein the outer cladding region comprises at least three outer cladding rings. 
     
     
         9 . The source of optical supercontinuum generation according to  claim 8 , wherein the average minimum width (w 2 ) of the at least three outer ring bridges is larger than about 1 μm. 
     
     
         10 . The source of optical supercontinuum generation according to  claim 2 , wherein a plurality of the outer cladding features have a characteristic diameter smaller than a first characteristic diameter (d 1 ) of the cladding features of at least one of the at least two inner rings. 
     
     
         11 . The source of optical supercontinuum generation according to  claim 2 , wherein the core region comprises a core background material which is doped with dopant material decreasing the refractive index of the core region compared to the core background material in undoped condition. 
     
     
         12 . The source of optical supercontinuum generation according to  claim 2 , wherein said core region has a substantially identical diameter along substantially the entire length of the microstructured optical fiber. 
     
     
         13 . The source of optical supercontinuum generation according to  claim 2 , wherein:
 said outer cladding features have a characteristic diameter having an average diameter (d 2 ), the cladding features of at least one of the at least two inner rings of the inner cladding region are arranged at a first pitch (λ 1 ) and have a first characteristic diameter (d 1 ) and the outer cladding features of the outer cladding region are arranged at a second pitch (λ 2 ), and the cladding features in at least one of the at least two inner rings of the inner cladding region have a first relative cladding feature size (d 1 /λ 1 ) and the outer cladding features in the outer cladding region have a second relative cladding feature size (d 2 /λ 2 ), where the difference (d 1 /λ 1 −d 2 /λ 2 ) between the first relative cladding feature size and the second relative cladding feature size is larger than about 0.1 and the second pitch is larger than the first pitch.   
     
     
         14 . The source of optical supercontinuum generation according to  claim 2 , wherein a first characteristic diameter (d 1 ) of the cladding features of at least one of the at least two inner rings is larger than about 1.5 μm. 
     
     
         15 . The source of optical supercontinuum generation according to  claim 12 , wherein a first characteristic diameter (d 1 ) of the cladding features of at least one of the at least two inner rings of the inner cladding region is smaller than the average diameter (d 2 ) of the features of the at least one ring of the outer cladding region. 
     
     
         16 . The source of optical supercontinuum generation according to  claim 2 , wherein the cladding features are gas filled voids, liquid filled voids, or glass having a lower refractive index than the cladding background material. 
     
     
         17 . The source of optical supercontinuum generation according to  claim 2 , wherein the core region of the microstructured fiber comprises a first refractive index and the inner cladding region comprises a second refractive index such that a Δ-value between the core region and a maximum refractive index for the cladding region as a whole is smaller than about 0.03. 
     
     
         18 . The source of optical supercontinuum generation according to  claim 2 , wherein the microstructured optical fiber has a zero dispersion wavelength of from about 860 nm to about 1400 nm. 
     
     
         19 . The source of optical supercontinuum generation according to  claim 2 , wherein the pump radiation comprises a pump wavelength which is between about 1000 nm and about 1100 nm and is up to about 200 nm above or below the zero dispersion wavelength of the microstructured optical fiber. 
     
     
         20 . The source of optical supercontinuum generation according to  claim 2 , comprising a cascade optical fiber comprising:
 (a) a first optical fiber in a form of said microstructured optical fiber, and   (b) a second optical fiber comprising a second core region that is capable of guiding light along a longitudinal axis of said second optical fiber and a second cladding region surrounding the second core region,   wherein a mode field diameter of the first microstructured optical fiber is larger than a mode field diameter of said second optical fiber, and wherein the first microstructured optical fiber is optically connected to the second optical fiber.   
     
     
         21 . The source of optical supercontinuum generation according to  claim 2 , wherein the microstructured optical fiber has an input end, wherein the microstructured optical fiber has, at least at its input end, is single mode at said pump wavelength.