A high-efficiency laser diode is provided. Since a λ/4 phase-shifted distributed feedback (DFB) laser diode has a great coupling coefficient, mode stability is poor due to spatial hole burning when multiplication of the coupling coefficient by length of a resonator is equal to or greater than 2. In the inventive concept, a region capable of controlling spatial hole burning is inserted into a semiconductor laser diode structure. Thus, an ultrahigh-speed pulse laser diode having a repetition rate in the band ranging from 100 GHz to 300 GHz is obtained. In addition, a single-mode laser diode with improved energy use efficiency is implemented by changing the configuration of a laser diode.