| 摘要 |
PURPOSE:To prevent the mode hop of laser light securely by generating multimode light which has more modes in an off period wherein laser light is not emitted, and thus raising the temperature of the joint part of a semiconductor laser and decreasing the temperature difference from the temperature in an off period. CONSTITUTION:The laser light 9 has single wavelength lambda1 in a period TB in which the semiconductor laser LD inputs a pulse 7 and turns on. A high frequency pulses 10 is superposed in an off period TA to generate multimode light having as many mode as possible, so each light component has small power. The multimode light emitted in the off period differ in wavelength, so light diffracted through a hologram 3 is dispersed and respective mode light components have small power, so light having weak intensity spreads widely over an irradiated surface 12, so no practical problem is generated.
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