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Dynamic enhancement of semiconductor lasers in the present of coherent feedback

A harmonic conversion approach is presented for the enhancement of the dynamic of semiconductor laser. By efficient transfer of power to the desired harmonic of a directly modulated semiconductor laser diode, the modulation bandwidth will be extended. The focus of this study is a laser diode with an external cavity, of which the resonant frequency matches to the fourth harmonic of the modulation signal. The number of modes of the laser with optical feedback is increased as the external cavity modes matches up with the Fabry-Perot cavity modes. The experimental results show that the fourth harmonic is enhanced by ¿ 23dB from the case of without feedback.