摘要 |
A laser beam is obtained from a semiconductor laser by a stable emission light amount. A first semiconductor laser is thermally coupled with a second semiconductor laser and driven by a feedback circuit constructed by a photodetector, an I-V converter, and a current generator so as to stabilize the emission light amount. A current I<SUB>0</SUB>' having a correlation with a drive current I<SUB>0 </SUB>of the 1st laser is outputted from a current mirror circuit. A modulation signal is supplied to a current pull-in type current driving circuit via a multiplier and a linearity compensating circuit and a current I<SUB>2 </SUB>according to the modulation signal is extracted from a collector of a transistor. The 2nd laser is driven by a current I<SUB>1 </SUB>(I<SUB>0</SUB>'-I<SUB>2</SUB>) and a laser beam modulated by the modulation signal is generated. Since the signal modulation by the 2nd laser is performed without influencing on I<SUB>0 </SUB>and the 2nd laser is driven by I<SUB>0</SUB>', the emission light amount is stabilized.
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