# US 2024/0201434 A1 · Hollow core optical fiber and a laser system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2024/0201434 A1 - Document ID: US20240201434A1 - Status: Published application - Kind: A1 - Application number: 18/590,369 - Filed: 2024-02-28 - Published: 2024-06-20 - Earliest claimed: 2015-12-23 - Assignees: Nkt Photonics A/S - Applicants: NKT Photonics A/S - Inventors: Jens Kristian Lyngsøe; Christian Jakobsen; Mattia Michieletto - Web page: https://patentgrep.com/patent/US20240201434A1 ## CPC - G02B 6/02328: {Hollow or gas filled core} - C03B 37/0122: {for making preforms of photonic crystal, microstructured or holey optical fibres} - C03B 2203/14: Non-solid, i.e. hollow products, e.g. hollow clad or with core-clad interface - C03B 2203/16: Hollow core - C03B 2203/42: Photonic crystal fibres, e.g. fibres using the photonic bandgap PBG effect, microstructured or holey optical fibres - G02B 6/02338: {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} - G02B 6/02366: {Single ring of structures, e.g. "air clad"} - G02B 6/02371: {Cross section of longitudinal structures is non-circular} - G02B 6/4206: {Optical features (G02B6/4207, G02B6/421 take precedence)} - G02B 6/4296: {coupling with sources of high radiant energy, e.g. high power lasers, high temperature light sources} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES ## Abstract A hollow core photonic crystal fiber (PCF) including an outer cladding region and seven hollow tubes surrounded by the outer cladding region. Each of the hollow tubes is fused to the outer cladding to form a ring defining an inner cladding region and a hollow core region surrounded by the inner cladding region. The hollow tubes are not touching each other but are arranged with distance to adjacent hollow tubes. The hollow tubes each have an average outer diameter d2 and an average inner diameter d1, wherein d1/d2 is equal to or larger than about 0.8, such as equal to or larger than about 0.85, such as equal to or larger than about 0.9. Also, a laser system. ## Claims ### Claim 1 A laser system for delivering laser light, the laser system comprising: a laser light source; and a fiber delivery cable for delivering light from the laser light source, wherein the fiber delivery cable comprises a hollow core photonic crystal fiber (PCF) comprising an outer cladding region and a plurality of hollow tubes surrounded by the outer cladding region, each of the hollow tubes having an average inner tube diameter d1 and an average outer tube diameter d2, where each of the hollow tubes is fused to the outer cladding region to form a ring defining an inner cladding region and a hollow core region surrounded by the inner cladding region, wherein at least one of the hollow tubes comprises a nested sub-tube having an average outer sub-tube diameter dsub smaller than the average inner diameter d1 of the hollow tube and arranged in the hollow structure of the hollow tube and fused to the hollow tube, wherein the outer cladding forms a first tubular element, and wherein the nested sub-tube forms a second tubular element with a third tubular element nested within the second tubular element, wherein each of the hollow tubes comprises a core center facing region with a wall thickness, and wherein the hollow core region and/or one or more of the plurality of hollow tubes is/are filled with gas that differs from air. ### Claim 2 (depends on 1) The laser system of claim 1, wherein at least one of the plurality of hollow tubes has a different wall thickness than at least one other of the plurality of hollow tubes. ### Claim 3 (depends on 1) The laser system of claim 1, wherein the hollow tubes are not touching each other. ### Claim 4 (depends on 1) The laser system of claim 1, wherein the nested sub-tube is fused to the hollow tube at its maximal radial distance to the core center axis. ### Claim 5 (depends on 1) The laser system of claim 1, wherein the hollow tubes have a center to center distance A between adjacent hollow tubes which center to center distance is between about 1.01*d2 and about 1.5*d2. ### Claim 6 (depends on 1) The laser system of claim 1, wherein the minimum distance between adjacent hollow tubes is at least about 0.1 μm. ### Claim 7 (depends on 1) The laser system of claim 1, wherein the hollow core region has a core diameter D defined as the diameter of the largest circle inscribed by the hollow tubes. ### Claim 8 (depends on 7) The laser system of claim 7, wherein the hollow core region diameter D is from about 10 μm to about 100 μm. ### Claim 9 (depends on 7) The laser system of claim 7, wherein the average outer tube diameter relative to the core diameter d2/D is from about 0.5 to about 0.75. ### Claim 10 (depends on 1) The laser system of claim 1, wherein the plurality of hollow tubes comprises 7 hollow tubes. ### Claim 11 (depends on 1) The laser system of claim 1, wherein the plurality of hollow tubes consists of 7 hollow tubes. ### Claim 12 (depends on 1) The laser system of claim 1, wherein the sub-tube average outer diameter dsub, is substantially smaller than the average inner diameter d1 of the hollow tube. ### Claim 13 (depends on 1) The laser system of claim 1, wherein the wall thickness is up to about 2.1 μm. ### Claim 14 (depends on 1) The laser system of claim 1, wherein the laser light source is a pulsed laser light source configured to generate pulses of laser light, wherein each of the pulses has a pulse duration between 30 fs and 30 ps. ### Claim 15 (depends on 1) The laser system of claim 1, wherein the light from the light source, determined at the exit of the laser light source, is at least about 5 kW. ### Claim 16 (depends on 1) The laser system of claim 1, wherein the gas is argon or a mixture comprising argon. ### Claim 17 (depends on 1) The laser system of claim 1, wherein the gas is pressurized to a pressure. ### Claim 18 (depends on 17) The laser system of claim 17, wherein the pressure is up to 2 bars at standard temperature. ### Claim 19 (depends on 1) The laser system of claim 1, wherein the hollow core PCF has a length between 1 m and 15 m. ### Claim 20 (depends on 19) The laser system of claim 19, wherein the hollow core PCF has a length between 5 m and 10 m. ### Claim 21 (depends on 1) The laser system of claim 1, wherein the hollow core PCF has a length of up to 50 m. ### Claim 22 (depends on 1) The laser system of claim 1, wherein the laser light source is a modelocked laser light source. ### Claim 23 (depends on 1) The laser system of claim 1, wherein the laser light source comprises one or more amplifiers. ### Claim 24 (depends on 1) The laser system of claim 1, wherein the laser light source and the hollow core PCF is configured to deliver a laser beam from the laser source and through the hollow core PCF such that the beam quality, M2, of the beam delivered through the hollow core PCF is 1.5 or less. ### Claim 25 (depends on 1) The laser system of claim 1, wherein the hollow core PCF is configured for single mode guiding of at least one wavelength in the range from about 200 nm to about 4.5 μm. ### Claim 26 (depends on 25) The laser system of claim 25, wherein the at least one wavelength is in the range from 1000 nm to about 1100 nm. ### Claim 27 (depends on 25) The laser system of claim 25, wherein the hollow core PCF is configured for guiding a continuum of light wavelengths, spanning over at least 0.5 μm. ### Claim 28 (depends on 1) The laser system of claim 1, wherein the hollow core PCF and the at least one nested sub-tube provides a transmission loss of less than 50 dB/km. ### Claim 29 (depends on 1) The laser system of claim 1, wherein the hollow core PCF and the at least one nested sub-tube provides a transmission efficiency of more than 90%. ### Claim 30 A laser system for delivering laser light, the laser system comprising: a laser light source; and a fiber delivery cable for delivering light from the laser light source, wherein the fiber delivery cable comprises a hollow core photonic crystal fiber (PCF) comprising an outer cladding region and a plurality of hollow tubes surrounded by the outer cladding region, each of the hollow tubes having an average inner tube diameter d1 and an average outer tube diameter d2, where each of the hollow tubes is fused to the outer cladding region to form a ring defining an inner cladding region and a hollow core region surrounded by the inner cladding region, wherein at least one of the hollow tubes comprises a nested sub-tube having an average outer sub-tube diameter dsub smaller than the average inner diameter d1 of the hollow tube and arranged in the hollow structure of the hollow tube and fused to the hollow tube, wherein the outer cladding forms a first tubular element, and wherein the nested sub-tube forms a second tubular element with a third tubular element nested within the second tubular element, wherein each of the hollow tubes comprises a core center facing region with a wall thickness, and wherein the hollow core region and/or one or more of the plurality of hollow tubes is/are evacuated from gas. ### Claim 31 (depends on 30) The laser system of claim 30, wherein at least one of the plurality of hollow tubes has a different wall thickness than at least one other of the plurality of hollow tubes. ### Claim 32 (depends on 30) The laser system of claim 30, wherein the hollow tubes are not touching each other. ### Claim 33 (depends on 30) The laser system of claim 30, wherein the nested sub-tube is fused to the hollow tube at its maximal radial distance to the core center axis. ### Claim 34 (depends on 30) The laser system of claim 30, wherein the hollow tubes have a center to center distance A between adjacent hollow tubes which center to center distance is between about 1.01*d2 and about 1.5*d2. ### Claim 35 (depends on 30) The laser system of claim 30, wherein the minimum distance between adjacent hollow tubes is at least about 0.1 μm. ### Claim 36 (depends on 30) The laser system of claim 30, wherein the hollow core region has a core diameter D defined as the diameter of the largest circle inscribed by the hollow tubes. ### Claim 37 (depends on 36) The laser system of claim 36, wherein the hollow core region diameter D is from about 10 μm to about 100 μm. ### Claim 38 (depends on 36) The laser system of claim 36, wherein the average outer tube diameter relative to the core diameter d2/D is from about 0.5 to about 0.75. ### Claim 39 (depends on 30) The laser system of claim 30, wherein the plurality of hollow tubes comprises 7 hollow tubes. ### Claim 40 (depends on 30) The laser system of claim 30, wherein the plurality of hollow tubes consists of 7 hollow tubes. ### Claim 41 (depends on 30) The laser system of claim 30, wherein the sub-tube average outer diameter dsub, is substantially smaller than the average inner diameter d1 of the hollow tube. ### Claim 42 (depends on 30) The laser system of claim 30, wherein the wall thickness is up to about 2.1 μm. ### Claim 43 (depends on 30) The laser system of claim 30, wherein the laser light source is a pulsed laser light source configured to generate pulses of laser light, wherein each of the pulses has a pulse duration between 30 fs and 30 ps. ### Claim 44 (depends on 30) The laser system of claim 30, wherein the light from the light source, determined at the exit of the laser light source, is at least about 5 kW. ### Claim 45 (depends on 30) The laser system of claim 30, wherein the hollow core region and/or one or more of the plurality of hollow tubes is/are evacuated from gas to a pressure of about 1 mbar or less, at standard temperature. ### Claim 46 (depends on 30) The laser system of claim 30, wherein the hollow core region and/or one or more of the plurality of hollow tubes is/are evacuated from gas to a pressure of about 0.1 mbar or less, at standard temperature. ### Claim 47 (depends on 30) The laser system of claim 30, wherein the hollow core region and/or one or more of the plurality of hollow tubes is/are evacuated from gas to a pressure of about 0.01 mbar or less, at standard temperature. ### Claim 48 (depends on 30) The laser system of claim 30, wherein the hollow core PCF has a length between 1 m and 15 m. ### Claim 49 (depends on 48) The laser system of claim 48, wherein the hollow core PCF has a length between 5 m and 10 m. ### Claim 50 (depends on 30) The laser system of claim 30, wherein the hollow core PCF has a length of up to 50 m. ### Claim 51 (depends on 30) The laser system of claim 30, wherein the laser light source is a modelocked laser light source. ### Claim 52 (depends on 30) The laser system of claim 30, wherein the laser light source comprises one or more amplifiers. ### Claim 53 (depends on 30) The laser system of claim 30, wherein the laser light source and the hollow core PCF is configured to deliver a laser beam from the laser source and through the hollow core PCF such that the beam quality, M2, of the beam delivered through the hollow core PCF is 1.5 or less. ### Claim 54 (depends on 30) The laser system of claim 30, wherein the hollow core PCF is configured for single mode guiding of at least one wavelength in the range from about 200 nm to about 4.5 μm. ### Claim 55 (depends on 54) The laser system of claim 54, wherein the at least one wavelength is in the range from 1000 nm to about 1100 nm. ### Claim 56 (depends on 54) The laser system of claim 54, wherein the hollow core PCF is configured for guiding a continuum of light wavelengths, spanning over at least 0.5 μm. ### Claim 57 (depends on 30) The laser system of claim 30, wherein the hollow core PCF and the at least one nested sub-tube provides a transmission loss of less than 50 dB/km. ### Claim 58 (depends on 30) The laser system of claim 30, wherein the hollow core PCF and the at least one nested sub-tube provides a transmission efficiency of more than 90%.