| 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 I0' having a correlation with a drive current I0 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 I2 according to the modulation signal is extracted from a collector of a transistor. The 2nd laser is driven by a current I1 (I0'-I2) and a laser beam modulated by the modulation signal is generated. Since the signal modulation by the 2nd laser is performed without influencing on I0 and the 2nd laser is driven by I0', the emission light amount is stabilized.
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