Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userRandom-laser dynamics with temporally modulated pump
458
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present an experimental study of the effects of temporal modulation of the pump intensity on a random laser. The nanosecond pump pulses exhibit rapid intensity fluctuations which differ from pulse to pulse. Specific temporal profiles of the pump pulses produce extraordinarily strong emission from the random laser. This process is deterministic and insensitive to the spatial configuration of the scatterers and spontaneous emission noise.
rate research
Read More
High-brightness electron bunches, such as those generated and accelerated in free-electron lasers (FELs), can develop small-scale structure in the longitudinal phase space. This causes variations in the slice energy spread and current profile of the bunch which then undergo amplification, in an effect known as the microbunching instability. By imposing energy spread modulations on the bunch in the low-energy section of an accelerator, using an undulator and a modulated laser pulse in the centre of a dispersive chicane, it is possible tomanipulate the bunch longitudinal phase space. This allows for the control and study of the instability in unprecedented detail. We report measurements and analysis of such modulated electron bunches in the 2Dspectro-temporal domain at the FERMI FEL, for three different bunch compression schemes. We also perform corresponding simulations of these experiments and show that the codes are indeed able to reproduce the measurements across a wide spectral range. This detailed experimental verification of the ability of codes to capture the essential beam dynamics of the microbunching instability will benefit the design and performance of future FELs.
Emerging photonic functionalities are mostly governed by the fundamental principle of Lorentz reciprocity. Lifting the constraints imposed by this principle could circumvent deleterious effects that limit the performance of photonic systems. A variety of approaches have recently been explored to break reciprocity, yet most efforts have been limited to confined photonic systems. Here, we propose and experimentally demonstrate a spatio-temporally modulated metasurface capable of extreme breakdown of Lorentz reciprocity. Through tailoring the momentum and frequency harmonic contents of the scattered waves, we achieve dynamical beam steering, reconfigurable focusing, and giant free-space optical isolation exemplifying the flexibility of our platform. We develop a generalized Bloch-Floquet theory which offers physical insights into the demonstrated extreme nonreciprocity, and its predictions are in excellent agreement with experiments. Our work opens exciting opportunities in applications where free-space nonreciprocal wave propagation is desired, including wireless communications and radiative energy transfer.
We investigate the effects of two dimensional confinement on the lasing properties of a classical random laser system operating in the incoherent feedback (diffusive) regime. A suspension of 250nm rutile (TiO2) particles in a Rhodamine 6G solution was inserted into the hollow core of a photonic crystal fiber (PCF) generating the first random fiber laser and a novel quasi-one-dimensional RL geometry. Comparison with similar systems in bulk format shows that the random fiber laser presents an efficiency that is at least two orders of magnitude higher.
The angular emission pattern of a random laser is typically very irregular and difficult to tune. Here we show by detailed numerical calculations that one can overcome the lack of control over this emission pattern by actively shaping the spatial pump distribution. We demonstrate, in particular, how to obtain customized pump profiles to achieve highly directional emission. Going beyond the regime of strongly scattering media where localized modes with a given directionality can simply be selected by the pump, we present an optimization-based approach which shapes extended lasing modes in the weakly scattering regime according to any predetermined emission pattern.
We cast a theoretical model based on Effective Semiconductor Maxwell-Bloch Equations and study the dynamics of a multi-mode mid-Infrared Quantum Cascade Laser in Fabry Perot with the aim to investigate the spontaneous generation of optical frequency combs. This model encompasses the key features of a semiconductor active medium such as asymmetric,frequency-dependent gain and refractive index as well as the phase-amplitude coupling of the field dynamics provided by the linewidth enhancement factor. Our numerical simulations are in excellent agreement with recent experimental results, showing broad ranges of comb formationin locked regimes, separated by chaotic dynamics when the field modes unlock. In the former case, we identify self-confined structures travelling along the cavity, while the instantaneous frequency is characterized by a linear chirp behaviour. In such regimes we show that OFC are characterized by concomitant and relevant amplitude and frequency modulation.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
