BEAM QUALITY CONTROL DEVICE AND LASER DEVICE USING SAME

A beam quality control device includes an optical fiber, a stress-applying portion, and a temperature controller. The optical fiber has a core and a cladding that surrounds an outer peripheral surface of the core. The stress-applying portion is in surface-contact with at least a portion of an outer peripheral surface of the optical fiber. The stress-applying portion has a coefficient of thermal expansion of the stress-applying portion that is different from a coefficient of thermal expansion of the cladding. The temperature controller controls a temperature of the stress-applying portion. The stress-applying portion contracts or expands due to the temperature being changed by the temperature controller such that a distribution of external force applied by the stress-applying portion to the cladding becomes non-uniform in a peripheral direction of the cladding. 1. A beam quality control device , comprising:an optical fiber having a core and a cladding that surrounds an outer peripheral surface of the core;a stress-applying portion that is in surface contact with at least a portion of an outer peripheral surface of the optical fiber and that has a coefficient of thermal expansion of the stress-applying portion that is different from a coefficient of thermal expansion of the cladding; anda temperature controller that controls a temperature of the stress-applying portion,wherein the stress-applying portion contracts or expands due to the temperature being changed by the temperature controller such that a distribution of an external force applied by the stress-applying portion to the cladding becomes non-uniform in a peripheral direction of the cladding.2. The beam quality control device according to claim 1 , further comprising:a heat-conducting plate, is thermally connected to the stress-applying portion and the temperature controller, and conducts heat between the temperature controller and the stress-applying portion, whereinthe stress-applying portion is disposed on ...