PURPOSE: To simply perform light short pulse single pulse oscillation and repetitive pulse oscillation of 10kHz or higher by employing a colorant laser amplifier for amplifying a laser beam from a semiconductor laser oscillator.

CONSTITUTION: A semiconductor laser 11, and a die laser amplifier 14 for amplifying a laser beam from the oscillator 11 are provided. When an excitation by a short pulse current having several ns or less of a current injection type semiconductor laser (diode laser) and a deep high frequency current modulation with several hundreds MHz are conducted a light short pulse laser beam having 100ps or below is generated by a relaxation oscillation. Such features are utilized to amplify the light short pulse of the laser by the amplifier 14 to power having ten times∼several thousands of times. Thus, even if a mode synchronizing method is not employed, a relatively high output light short pulse 20 useful for use in a measurement of a substance high speed phenomenon and various measurements can be obtained.