Abstract
Here we consider coherent mode-locking (CML) regimes in single-section cavity lasers, taking place for pulse durations less than atomic population and phase relaxation times, which arise due to coherent Rabi oscillations of the atomic inversion. Typically, CML is introduced for lasers with two sections, the gain and absorber ones. Here we show that, for certain combination of the cavity length and relaxation parameters, a very stable CML in a laser, containing only gain section, may arise. The mode-locking is unconditionally self-starting and appears due to balance of intra-pulse de-excitation and slow interpulse-scale pump-induced relaxation processes. We also discuss the scaling of the system to shorter pulse durations, showing a possibility of mode-locking for few-cycle pulses.
Highlights
We consider coherent mode-locking (CML) regimes in single-section cavity lasers, taking place for pulse durations less than atomic population and phase relaxation times, which arise due to coherent Rabi oscillations of the atomic inversion
Typical for applications is so called passive mode-locking (PML), achieved by incorporating a nonlinear absorber with suitable properties into the laser cavity. In such two-section cavities, generation of short pulses is achieved due to saturation of the amplifier/absorber section, and the pulse duration τp is larger than the polarization relaxation time T2 in the amplifier and absorber sections
CML can arise if the absorber section works in the coherent regime[19,20,21] whereas the amplifier section is in the saturable regime
Summary
An important quantity describing the pulse dynamics in the coherent regime is the pulse area, defined a s9. Using the area theorem Eq (2) and branches of it’s solution (similar to that plotted in Fig. 1) we are able to follow the evolution of the pulse area during a single round-trip in a ring laser cavity. After the pulse passes the amplifier, it is reflected by a non-ideal mirror and its area is reduced according to Eq (10), what corresponds to the moving of the point on the diagram Fig. 3 along the curve 23 from right to left to the point 3. That after many round-trips a stable self-pulsating regime with pulse having the area in the vicinity of π , sets up
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