Effective bandwidth for FM noise suppression in an injection-locked semiconductor laser

Noise characteristics of single-mode semiconductor lasers under external light injection

“…4) The master laser, to a large extent, determines the noise characteristics in the locking regime. This result, in some way, is in line with the phase noise analysis presented in [21]. Obviously, the noise of the master laser cannot systematically be ignored in the noise model of the slave laser subject to optical injection.…”

Frequency noise suppression of optical injection-locked quantum cascade lasers

“…This is because the low-frequency phase of the slave laser is strongly locked to that of the master laser without any noise. In case the rate equations take into account the optical noise of the master laser, which has no correlation with that of the slave laser, the low-frequency FN will be the same as that of the master laser [34][35][36]. Therefore, like injection-locked interband lasers, the spectral linewidth of the injection-locked QCL is only governed by the FN of the master laser, and no longer follows the Schawlow-Townes limit of the free-running laser [34].…”

“…However, a more rigorous definition of the FN suppression bandwidth for QCLs is required in future work. For interband lasers, the FN suppression bandwidth is found to be half-width of the stable locking bandwidth at α H = 0 [34,35]. In order to characterize the FN suppression effect, the suppression ratio of the FN peak is defined as the peak amplitude of the freerunning laser divided by that of the injection-locked laser.…”