Frequency locking by master lasers with intrinsic linewidth ranging from millihertz to megahertz

Our study focuses on the transfer of coherence through the optical injection of semiconductor distributed feedback (DFB) lasers. We use master lasers with linewidths ranging from millihertz to megahertz. The significant disparity in linewidth between the master and slave lasers allows us to examine the effect of coherence on frequency locking. Our experimental results demonstrate that frequency locking depends on the properties of frequency noise. For instance, the minimum optical power required to achieve frequency locking also depends on these noise properties. This study sheds new light on coherence-transfer dynamics in systems with an extreme linewidth mismatch. It also paves the way for the development of compact, low-noise, frequency-stable semiconductor laser sources for advanced photonic applications.