Quantum-dot semiconductor lasers with prominent relative intensity noise and spectral characteristics.

Relative intensity noise (RIN) behavior of a quantum dot laser (QDL) at free running and under optical injection locking (OIL) has been reported in detail. Considering the mutual effects of the inhomogeneous and homogeneous broadenings, different and also non-routine RIN characteristics of a QDL at low, intermediate, and high homogeneous broadening regimes have been discussed. Results demonstrate that an injection-locked quantum dot laser exhibit enhanced characteristic over free-running operation along with low-frequency noise behavior in a wide range of homogeneous broadening values. RIN reduction of about 25, 55, and 7 dB/Hz have been achieved for low, intermediate, and high values of homogeneous broadening which implies the spontaneous emission noise suppression even at low injection power. The promising impact of the OIL on side-mode suppression for the intermediate homogeneous broadening regime has also been discussed. Our results guarantee the single-mode and low-noise operation of the OIL-QDL at any homogeneous broadening value.