FREQUENCY CONTROL OF SELF-SUSTAINED PULSATING LASER-DIODES BY UNIFORMIMPURITY DOPING INTO MULTIPLE-QUANTUM-WELL STRUCTURES

The self-sustained pulsating frequency in index-guided AlGaAs multiple -quantum-well (MQW) laser diodes is controlled by impurity doping into the active region to reduce the relative intensity noise induced by o ptical feedback through a short optical path, Uniform n-type impurity doping into an MQW structure more effectively reduces the frequency by decreasing the differential gain than does modulation doping with an n-type impurity, Uniform doping of 1 x 10(18) cm(-3) into each quantum well. layer reduces the frequency to less than 0.8 GHz, which corresp onds to half or two-thirds that of undoped lasers, The uniformly n-dop ed self-sustained pulsating lasers provided low-noise characteristics with a relative intensity noise below 1 x 10(-13) Hz(-1) under an opti cal feedback of 20% even with a short optical path length of 60 mm.