arXiv subjects
Publications and source records attributed to Hani Kbashi.
We experimentally evaluated the sensing-communication trade-off from the fixed-point precision MIMO equalizer using FPGA. At 7-bit, noise floor drops 100x and angular error 63%, but the communication performance saturates while the hardware complexity rises.
Synchronization is ubiquitous across a wide range of fields. Subharmonic entrainment (SHE) is a nonlinear synchronization phenomenon that results in a locking oscillator at a frequency of an external periodic forcing signal with a fraction of the oscillator frequency. Beyond the fundamentals of nonlinear dynamics, SHE has a range of practical applications from stabilizing ultrafast laser pulses to optimizing control in various engineering and natural systems. However, the vectorial nature of SHE remains elusive. Here, we present the results of a theoretical and experimental study of a vector type of subharmonic entrainment (VSHE) using a passively mode-locked fiber laser as a testbed. We unveil the mechanism of vectorial SHE, in which weak external signals can entrain internal laser dynamics through vectorial coupling. Vectorial SHE presents in the form of synchronization between the subharmonic of mode-locking-driven oscillations and continuous wave (CW) signal through an evolving state of polarization. This CW signal, driven by the internal dynamics of the injected signal, causes VSHE with the frequencies ratios of multiples of ten, resulting in a partially mode-locking regime operation. Our findings offer new control techniques over mode-locking and additional dimension such as polarization states.
Mode-locked lasers play the role of the ideal testbeds for studying self-coherent structures, dissipative solitons, with stable spatiotemporal profiles supported by the balance between dispersion and nonlinearity. However, under some conditions, the profile and energy of the solitons can oscillate (breath) periodically. Unlike the previous studies of different scalar mechanisms of breathers emergence, we demonstrate experimentally and theoretically a new vector mechanism where breathing of the output power is a result of the heteroclinic dynamics. The heteroclinic orbit is a trajectory periodically evolving nearby the neighborhood of one of the orthogonal states of polarization with further switching to and evolving nearby the other state of polarization. The dwelling time for the trajectory near each orthogonal state is determined by the cavity anisotropy adjustable with the help of the polarization controller for the pump wave. The obtained results on tunability of breathing dynamics enables unlocking novel techniques of the flexible control and manipulation of the polarization dynamics of dissipative solitons.
Soliton rain is a bunch of small soliton pulses slowly drifting nearby the main pulse having the period of a round trip. For Er-doped fiber laser mode-locked by carbon nanotubes, for the first time, we demonstrate both experimentally and theoretically a new type of polarization attractors controllable by the vector soliton rain. With adjusting the pump power, vector soliton rain takes the form of pulses with rotating states of polarization which enable transforming slowly evolving trajectories on the Poincaré sphere from the double-scroll spiral to the circle. The obtained results on controlling complex multisoliton dynamics can be of interest in laser physics and engineering with potential applications in spectroscopy, metrology, and biomedical diagnostics.