# US 8,542,711 B2 · Fiber laser device

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- Number: US 8,542,711 B2
- Document ID: US8542711B2
- Status: Granted
- Kind: B2
- Application number: 13/628,836
- Filed: 2012-09-27
- Published: 2013-01-24
- Granted: 2013-09-24
- Earliest claimed: 2010-03-31
- Assignees: Fujikura Ltd.
- Applicants: Fujikura Ltd.
- Inventors: Kotaro Shimokoshi
- Web page: https://patentgrep.com/patent/US8542711B2

## CPC

- H01S 3/09415: {the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping}
- H01S 3/1001: {by controlling the optical pumping}
- H01S 5/06808: {by monitoring the electrical laser parameters, e.g. voltage or current}
- H01S 3/06754: {Fibre amplifiers (H01S3/06708 takes precedence)}
- H01S 3/09408: {Pump redundancy}
- H01S 5/0428: {for applying pulses to the laser}
- H01S 5/0617: {using memorised or pre-programmed laser characteristics}
- H01S 5/06216: {Pulse modulation or generation}
- H01S 5/4018: {Lasers electrically in series}
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL

## Abstract

A laser diode driving device (1) of the present invention includes: a variable DC power supply (3) for outputting a voltage for driving laser diodes (LD1 to LDn); a current driving element (4) for causing a current If to flow; a current control section (5) for controlling (i) turning on and off of the current driving element (4) and (ii) the amount of the current If; and a power supply control section (7) for controlling an output voltage of the variable DC power supply (3). The power supply control section (7) controls, on the basis of If-Vf characteristic data (D2), voltage drop characteristic data (D3), and Vds setting data (D4) all stored in a memory section (8), the output voltage of the variable DC power supply (3) so that the current driving element (4) has a constant inter-terminal voltage regardless of the amount of the current If.

## Claims

### Claim 1

A fiber laser device comprising:
an amplification fiber;
an excitation light source for exciting the amplification fiber; and
a light source driving device for driving the excitation light source,
the light source driving device including:
a variable power supply for outputting a voltage for driving a semiconductor light source;
a current driving element for causing a current to flow through the semiconductor light source, the current driving element being connected to the semiconductor light source in series;
a current control section for controlling (i) turning on and off of the current driving element and (ii) an amount of the current; and
a power supply control section for controlling the voltage outputted by the variable power supply,
the light source driving device further comprising:
a storage section storing (i) current-voltage characteristic data indicative of a characteristic of a forward voltage of the semiconductor light source with respect to the current and (ii) voltage drop characteristic data indicative of a characteristic of a voltage drop at a resistance with respect to the current, the resistance being of a component of a circuit constituted by the variable power supply, the semiconductor light source, and the current driving element, the component being a component other than the semiconductor light source and the current driving element,
the current control section, in a case of switching amounts of the current, causing the current driving element to be off during an intermediate period between (i) a first period during which the current before the switch flows and (ii) a second period during which the current after the switch flows,
the power supply control section changing the output voltage during the intermediate period on a basis of the current-voltage characteristic data and the voltage drop characteristic data so that a difference between (i) a voltage across controlled terminals of the current driving element during the first period and (ii) the voltage across the controlled terminals of the current driving element during the second period has a value smaller than a value of the difference for a case in which the output voltage is constant throughout the first period and the second period.

### Claim 2 (depends on 1)

The fiber laser device according to claim 1,
wherein:
the power supply control section, regardless of the amount of the current, controls the output voltage so that the voltage across the controlled terminals is constant.

### Claim 3 (depends on 2)

The fiber laser device according to claim 2,
wherein:
the voltage across the controlled terminals is a minimum voltage that allows the current control section to control the amount of the current.

### Claim 4 (depends on 3)

The fiber laser device according to claim 3,
wherein:
the light source driving device further includes a temperature sensor for detecting a temperature of the semiconductor light source;
the storage section further stores temperature characteristic data indicative of a temperature characteristic of the forward voltage of the semiconductor light source; and
the power supply control section controls the output voltage on a basis of the current-voltage characteristic data, the voltage drop characteristic data, and the temperature characteristic data.

### Claim 5 (depends on 4)

The fiber laser device according to claim 4,
wherein:
the storage section further stores voltage setting data indicative of a setting value for the voltage across the controlled terminals; and
the power supply control section (i) calculates, on a basis of the current-voltage characteristic data and the temperature characteristic data, the forward voltage of the semiconductor light source with respect to (a) the amount of the current that the current driving element causes to flow and (b) the temperature detected by the temperature sensor, (ii) calculates, on a basis of the voltage drop characteristic data, the voltage drop at the resistance with respect to the amount of the current that the current driving element causes to flow, and (iii) controls the output voltage so that a sum of a value of the calculated forward voltage, a value of the calculated voltage drop, and the setting value equals a value of the output voltage.

### Claim 6 (depends on 3)

The fiber laser device according to claim 3,
wherein:
the storage section further stores voltage setting data indicative of a setting value for the voltage across the controlled terminals; and
the power supply control section (i) calculates, on a basis of the current-voltage characteristic data, the forward voltage of the semiconductor light source with respect to the amount of the current that the current driving element causes to flow, (ii) calculates, on a basis of the voltage drop characteristic data, the voltage drop at the resistance with respect to the amount of the current that the current driving element causes to flow, and (iii) controls the output voltage so that a sum of a value of the calculated forward voltage, a value of the calculated voltage drop, and the setting value equals a value of the output voltage.

### Claim 7 (depends on 2)

The fiber laser device according to claim 2,
wherein:
the light source driving device further includes a temperature sensor for detecting a temperature of the semiconductor light source;
the storage section further stores temperature characteristic data indicative of a temperature characteristic of the forward voltage of the semiconductor light source; and
the power supply control section controls the output voltage on a basis of the current-voltage characteristic data, the voltage drop characteristic data, and the temperature characteristic data.

### Claim 8 (depends on 7)

The fiber laser device according to claim 7,
wherein:
the storage section further stores voltage setting data indicative of a setting value for the voltage across the controlled terminals; and
the power supply control section (i) calculates, on a basis of the current-voltage characteristic data and the temperature characteristic data, the forward voltage of the semiconductor light source with respect to (a) the amount of the current that the current driving element causes to flow and (b) the temperature detected by the temperature sensor, (ii) calculates, on a basis of the voltage drop characteristic data, the voltage drop at the resistance with respect to the amount of the current that the current driving element causes to flow, and (iii) controls the output voltage so that a sum of a value of the calculated forward voltage, a value of the calculated voltage drop, and the setting value equals a value of the output voltage.

### Claim 9 (depends on 2)

The fiber laser device according to claim 2,
wherein:
the storage section further stores voltage setting data indicative of a setting value for the voltage across the controlled terminals; and
the power supply control section (i) calculates, on a basis of the current-voltage characteristic data, the forward voltage of the semiconductor light source with respect to the amount of the current that the current driving element causes to flow, (ii) calculates, on a basis of the voltage drop characteristic data, the voltage drop at the resistance with respect to the amount of the current that the current driving element causes to flow, and (iii) controls the output voltage so that a sum of a value of the calculated forward voltage, a value of the calculated voltage drop, and the setting value equals a value of the output voltage.

### Claim 10 (depends on 1)

The fiber laser device according to claim 1,
wherein:
the light source driving device further includes a temperature sensor for detecting a temperature of the semiconductor light source;
the storage section further stores temperature characteristic data indicative of a temperature characteristic of the forward voltage of the semiconductor light source; and
the power supply control section controls the output voltage on a basis of the current-voltage characteristic data, the voltage drop characteristic data, and the temperature characteristic data.

### Claim 11 (depends on 10)

The fiber laser device according to claim 10,
wherein:
the storage section further stores voltage setting data indicative of a setting value for the voltage across the controlled terminals; and
the power supply control section (i) calculates, on a basis of the current-voltage characteristic data and the temperature characteristic data, the forward voltage of the semiconductor light source with respect to (a) the amount of the current that the current driving element causes to flow and (b) the temperature detected by the temperature sensor, (ii) calculates, on a basis of the voltage drop characteristic data, the voltage drop at the resistance with respect to the amount of the current that the current driving element causes to flow, and (iii) controls the output voltage so that a sum of a value of the calculated forward voltage, a value of the calculated voltage drop, and the setting value equals a value of the output voltage.

### Claim 12 (depends on 1)

The fiber laser device according to claim 1,
wherein:
the storage section further stores voltage setting data indicative of a setting value for the voltage across the controlled terminals; and
the power supply control section (i) calculates, on a basis of the current-voltage characteristic data, the forward voltage of the semiconductor light source with respect to the amount of the current that the current driving element causes to flow, (ii) calculates, on a basis of the voltage drop characteristic data, the voltage drop at the resistance with respect to the amount of the current that the current driving element causes to flow, and (iii) controls the output voltage so that a sum of a value of the calculated forward voltage, a value of the calculated voltage drop, and the setting value equals a value of the output voltage.