Transient and sustained mode-locking of cavity solitons in a VCSEL with frequency-selective feedback

Self-confinement of light and the control of light by light are both major thrusts of modern photonics. Recently, optically controllable microlasers were realized within the aperture of a broad-area vertical-cavity surface-emitting laser (VCSEL) with frequency selective feedback and interpreted as cavity solitons (CS), i.e. as spatially self-localized nonlinear states. Like any free-running laser, a lasing CS has the freedom to choose polarization, phase and frequency, which gives exciting new opportunities for fundamental studies and applications. In particular this implies that the microlasers might operate on multiple longitudinal cavity modes leading to self-pulsing, if the modes are locked in phase. This is interesting in its own right but the intriguing long-term vision is that mode-locked spatial laser solitons might lead to full three-dimensional confinement or spatio-temporal light bullets where the pulse length and duration are smaller that the cavity length and round-trip time, respectively.