Patent ID: 8503496
Filing Date: 2013-08-06
Classification: H01S

Abstract:
1. A device for judging a state of a semiconductor laser, the device comprising: a providing unit that provides a driving electric current to the semiconductor laser, the electric current being superimposed a first alternating current signal having a first frequency at a low side of an operational range of the semiconductor laser and a second alternating current signal having a second frequency different from the first frequency at a high side of the operational range; a first filter that extracts a first component corresponding to the first frequency from a voltage to be applied to the semiconductor laser; a second filter that extracts a second component corresponding to the second frequency from the voltage to be applied to the semiconductor laser; and a judge circuit that judges a state of the semiconductor laser based on a first differential resistance obtained from the result of the extracting by the first filter and a second differential resistance obtained from the result of the extracting by the second filter, wherein the first frequency and the second frequency are smaller than a frequency of a digital signal of the driving electric current.