Fiber laser device

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.