FORMATION OF MODE FIELD CONVERSION OPTICAL WAVEGUIDE AND FORMING DEVICE THEREFOR

PROBLEM TO BE SOLVED: To provide a method and device for rapidly expanding the mode field of a quartz optical waveguide to a desired mode field at a low cost. SOLUTION: This device consists of a CO2 laser 1, a CO2 laser optical waveguide 2 which introduces the exit light from the CO2 laser 1 to the quartz optical waveguide 7 and controls the irradiation power quantity thereof and an optical waveguide element holder 3 which holds the quartz optical waveguide 7 in the position where the optical waveguide can be irradiated with the CO2 , laser light. The device has the optical waveguide element holder 3 which is capable of moving the quartz optical waveguide 7 at an arbitrary speed in the uniaxial direction in at least a horizontal direction and a lens 4 which condenses the CO2 laser light to the quartz optical waveguide 7. In addition, the device has a lens driving mechanism 5 which is capable of changing the spacing between the lens 4 and the quartz optical waveguide 7 at an arbitrary speed.