High-contrast 852-nm nanosecond laser pulse generation via injection-locking-assisted interferometric phase switching

We demonstrate a high-contrast 852-nm nanosecond pulse-generation scheme based on injection locking and interferometric phase switching. The system employs a master laser and an injection-locked slave laser whose outputs coherently interfere on a beam splitter (BS). By actively stabilizing the interferometer at the destructive-interference condition, one output port is maintained as a dark port. A nanosecond-scale π -phase shift applied to the injected seed is transferred to the slave-laser output through injection locking, thereby switching the interference condition and generating an intensity pulse at the dark port of the BS. With the aid of polarization-maintaining single-mode fiber filtering, the generated pulses reach a peak power of 100 mW with a measured power extinction ratio of 28.27 dB. After adding an additional spectral filtering module, the measured power extinction ratio is improved to 47.7 dB, corresponding to 62.8 mW in the ON state and 1.07 μ W in the OFF state. Taking into account the strong detuning dependence of resonant atomic scattering for the residual OFF-state spectrum, the effective extinction ratio relevant to resonant excitation exceeds 70 dB. This pulse generation scheme offers a simple pathway toward high-contrast nanosecond pulses, making it well suited for temporally well-defined resonant excitation, with the strong OFF-state suppression minimizing re-excitation and background scattering between pulses.