# US 10,310,177 B2 · Photonic crystal fiber

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- Number: US 10,310,177 B2
- Document ID: US10310177B2
- Status: Granted
- Kind: B2
- Application number: 15/563,988
- Filed: 2016-03-22
- Published: 2018-06-21
- Granted: 2019-06-04
- Earliest claimed: 2015-04-14
- Assignees: Nippon Telegraph and Telephone Corporation
- Applicants: Nippon Telegraph and Telephone Corporation
- Inventors: Takashi Matsui; Kyozo Tsujikawa; Fumihiko Yamamoto; Nobutomo Hanzawa
- Web page: https://patentgrep.com/patent/US10310177B2

## CPC

- G02B 6/02295: {Microstructured optical fibre (polarisation properties thereof G02B6/105 and G02B6/024)}
- G02B 6/02009: {Large effective area or mode field radius, e.g. to reduce nonlinear effects in single mode fibres}
- G02B 6/02023: {Based on higher order modes, i.e. propagating modes other than the LP01 or HE11 fundamental mode (mode converters G02B6/14)}
- G02B 6/02314: {Plurality of longitudinal structures extending along optical fibre axis, e.g. holes}
- G02B 6/02328: {Hollow or gas filled core}
- G02B 6/02309: {Structures extending perpendicularly or at a large angle to the longitudinal axis of the fibre, e.g. photonic band gap along fibre axis}
- G02B 6/02347: {Longitudinal structures arranged to form a regular periodic lattice, e.g. triangular, square, honeycomb unit cell repeated throughout cladding}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An object of the present invention is to provide a structure of an optical fiber capable of satisfying desired requirements of an output power, a propagation distance, and a beam quality. In the design of the PCF of the present invention, the PCF has air holes having diameters d and intervals Λ in an overlapping region where a region of Aeff of a desired value or more and a cutoff region in a desired higher-order mode overlap each other on a graph where the horizontal axis represents d/Λ and the vertical axis represents Λ, so that it is possible to sufficiently cut off the mode which is the desired higher-order mode or more, and thus, it is possible to select a region where the Aeff is large.

## Claims

### Claim 1

A photonic crystal fiber (PCF),
wherein the PCF is for laser processing,
wherein the PCF has a 1-cell structure in which an effective area Aeff is 800 μm2 or more, a bending loss in a fundamental mode with a bending radius of 140 mm is 1.0 dB/m or less in light having a wavelength of 1070 nm, and air holes having diameters d are arranged at intervals Λ, wherein the air holes extend in a propagation direction of light,
wherein a number of propagation modes is set to 2 or more and 4 or less to raise an index of beam quality M2 of output light up to 3.3, by including the air holes having diameters d and intervals Λ in a design region surrounded by a polygon having vertices
A2 (0.47, 25.31),
C2 (0.78, 35.00),
C3 (0.90, 54.38),
D2 (0.80, 35.93),
E (0.80, 45.63),
F (0.83, 51.56), and
I (0.90, 91.88), and
wherein coordinates are represented by (d/Λ, Λ), and a propagation of 30 kW·m or more and 150 kW·m or less is enabled for light having a wavelength of 1050 nm or more.

### Claim 2 (depends on 1)

The PCF according to claim 1,
wherein the air holes are surrounded by a polygon having vertices
A2 (0.48, 25.31),
C2 (0.69, 31.88),
D (0.74, 43.12),
E (0.75, 44.38),
F (0.81, 60.63),
G (0.85, 60.63),
H (0.85, 77.50), and
I (0.90, 91.88),
in the design region, and
the index of beam quality M2 of the output light is set up to 2.

### Claim 3

A photonic crystal fiber (PCF),
wherein the PCF is for laser processing,
wherein the PCF has a 1-cell structure in which an effective area Aeff is 1600 μm2 or more, a bending loss in a fundamental mode with a bending radius of 140 mm is 1.0 dB/m or less in light having a wavelength of 1070 nm, and air holes having diameters d are arranged at intervals Λ, wherein the air holes extend in a propagation direction of light,
wherein a number of propagation modes is set to 2 or more and 4 or less to raise an index of beam quality M2 of output light up to 3.3, by including the air holes having diameters d and intervals Λ in a design region surrounded by a polygon having vertices
A3 (0.56, 40.00),
C3 (0.90, 54.38), and
I (0.90, 91.88), and
wherein coordinates are represented by (d/Λ, Λ), and a propagation of 30 kW·m or more and 300 kW·m or less is enabled for light having a wavelength of 1050 nm or more.

### Claim 4 (depends on 3)

The PCF according to claim 3,
wherein the air holes are surrounded by a polygon having vertices
A3 (0.57, 40.00),
C3 (0.76, 47.81),
F (0.81, 60.63),
G (0.85, 60.63),
H (0.85, 77.50), and
I (0.90, 91.88),
in the design region, and
the index of beam quality M2 of the output light is set up to 2.

### Claim 5

A photonic crystal fiber (PCF),
wherein the PCF is for laser processing,
wherein the PCF has a 7-cell structure in which an effective area Aeff is 800 μm2 or more, a bending loss in a fundamental mode with a bending radius of 140 mm is 1.0 dB/m or less in light having a wavelength of 1070 nm, and air holes having diameters d are arranged at intervals Λ, wherein the air holes extend in a propagation direction of light,
wherein a number of propagation modes is set to 2 or more and 4 or less to raise an index of beam quality M2 of output light up to 3.3, by including the air holes having diameters d and intervals Λ in a design region surrounded by a polygon having vertices
A2 (0.21, 11.77),
C2 (0.50, 13.68),
C3 (0.60, 20.18),
F (0.50, 14.47),
G (0.69, 22.08),
H (0.68, 23.67),
I (0.70, 24.30),
J (0.70, 32.87), and
K (0.80, 50.00), and
wherein coordinates are represented by (d/Λ, Λ), and a propagation of 30 kW·m or more and 150 kW·m or less is enabled for light having a wavelength of 1050 nm or more.

### Claim 6 (depends on 5)

The PCF according to claim 5,
wherein the air holes are surrounded by a polygon having vertices
A2 (0.21, 11.77),
C2 (0.40, 12.88),
C3 (0.60, 20.34),
F (0.40, 13.52),
G (0.49, 14.15),
H (0.49, 15.74),
I (0.50, 18.12),
J (0.58, 18.12),
K (0.58, 19.86),
L (0.60, 23.03),
M (0.68, 23.99),
N (0.68, 31.60),
O (0.79, 48.73), and
P (0.80, 50.00),
in the design region, and
the index of beam quality M2 of the output light is set up to 2.

### Claim 7

A photonic crystal fiber (PCF),
wherein the PCF is for laser processing,
wherein the PCF has a 7-cell structure in which an effective area Aeff is 1600 μm2 or more, a bending loss in a fundamental mode with a bending radius of 140 mm is 1.0 dB/m or less in light having a wavelength of 1070 nm, and air holes having diameters d are arranged at intervals Λ, wherein the air holes extend in a propagation direction of light,
wherein a number of propagation modes is set to 2 or more and 4 or less to raise an index of beam quality M2 of output light up to 3.3, by including the air holes having diameters d and intervals Λ in a design region surrounded by a polygon having vertices
A3 (0.27, 16.06),
C3 (0.60, 20.18),
G (0.69, 22.08),
H (0.68, 23.67),
I (0.70, 24.30),
J (0.70, 32.87), and
K (0.80, 50.00), and
wherein coordinates are represented by (d/Λ, Λ), and a propagation of 30 kW·m or more and 300 kW·m or less is enabled for light having a wavelength of 1050 nm or more.

### Claim 8 (depends on 7)

The PCF according to claim 7,
wherein the air holes are surrounded by a polygon having vertices
A3 (0.27, 16.06),
C3 (0.60, 20.34),
L (0.60, 23.03),
M (0.68, 23.99),
N (0.68, 31.60),
O (0.79, 48.73), and
P (0.80, 50.00),
in the design region, and
the index of beam quality M2 of the output light is set up to 2.

### Claim 9

A photonic crystal fiber (PCF),
wherein the PCF is for laser processing,
wherein the PCF has a 7-cell structure in which an effective area Aeff is 3200 μm2 or more, a bending loss in a fundamental mode with a bending radius of 140 mm is 1.0 dB/m or less in light having a wavelength of 1070 nm, and air holes having diameters d are arranged at intervals Λ, wherein the air holes extend in a propagation direction of light,
wherein a number of propagation modes is set to 2 or more and 4 or less to raise an index of beam quality M2 of output light up to 3.3, by including the air holes having diameters d and intervals Λ in a design region surrounded by a polygon having vertices
A4 (0.40, 24.78),
C4 (0.70, 30.01),
J (0.70, 32.87), and
K (0.80, 50.00), and
wherein coordinates are represented by (d/Λ, Λ), and a propagation of 30 kW·m or more and 600 kW·m or less is enabled for light having a wavelength of 1050 nm or more.

### Claim 10 (depends on 9)

The PCF according to claim 9,
wherein the air holes are surrounded by a polygon having vertices
A4 (0.40, 24.46),
C4 (0.68, 29.56),
N (0.68, 31.60),
O (0.79, 48.73), and
P (0.80, 50.00),
in the design region, and
the index of beam quality M2 of the output light is set up to 2.

### Claim 11

A photonic crystal fiber (PCF),
wherein the PCF is for laser processing,
wherein the PCF has a 7-cell structure in which an effective area Aeff is 4800 μm2 or more, a bending loss in a fundamental mode with a bending radius of 140 mm is 1.0 dB/m or less in light having a wavelength of 1070 nm, and air holes having diameters d are arranged at intervals Λ, wherein the air holes extend in a propagation direction of light,
wherein a number of propagation modes is set to 2 or more and 4 or less to raise an index of beam quality M2 of output light up to 3.3, by including the air holes having diameters d and intervals Λ in a design region surrounded by a polygon having vertices
A5 (0.53, 32.87),
C5 (0.73, 37.00), and
K (0.80, 50.00), and
wherein coordinates are represented by (d/Λ, Λ), and a propagation of 30 kW·m or more and 900 kW·m or less is enabled for light having a wavelength of 1050 nm or more.

### Claim 12 (depends on 11)

The PCF according to claim 11,
wherein the air holes are surrounded by a polygon having vertices
A5 (0.53, 32.87),
C5 (0.72, 36.35),
O (0.79, 48.73), and
P (0.80, 50.00),
in the design region, and
the index of beam quality M2 of the output light is set up to 2.