arXiv subjects

Hamdi Barkaoui

Publications and source records attributed to Hamdi Barkaoui.

3 recordsLinked to original sources

arXiv2026

Bound state in the continuum induced room-temperature superfluorescence

Superfluorescence is a collective emission from several quantum emitters that initially have random phases and are then synchronized through vacuum field interactions. Despite its fascinating prospects in quantum information processing, optical computing and advanced photonic devices, a key challenge in harnessing superfluorescence is alleviating its reliance on cryogenic conditions. Recently, room-temperature superfluorescence has been successfully achieved using upconverted nanoparticles and quasi two-dimensional lead halide perovskites. These approaches, however, are restricted to a few specific material designs and unsuitable for wide promotion. Here, we report a universal strategy to elevate the operating temperature of superfluorescence. We reveal that the symmetry-protected optical bound state in the continuum (BIC) can break the size limitation of superfluorescence (λ^3) and correlate distant but similar emitters without violating the selection rules, significantly accelerating synchronization process and promoting the possibility of room-temperature superfluorescence. This effect has been experimentally verified using a series of BIC metasurfaces made of different lead halide perovskites. Key features such as the quadratic increase in transient peak intensity and the reduction in pulse width and build-up time at the BIC wavelength confirm the realization of room-temperature superfluorescence that is absent in the pristine material. A theoretical model is also built to explain the experimental observations. This research demonstrates that the operating temperatures of coherent macroscopic states can be effectively improved by artificial field, paving a critical step towards constructing building blocks for optical and quantum applications.

physics.optics↗

arXiv2025

Nonlinear chiral light generation from resonant metasurfaces

Chiral nonlinear response has been explored for decades due to its extreme sensitivity to molecular and structural dissymmetry. Conventional approaches often require bulky systems and produce only static nonlinear chirality. Here, we report on a generic mechanism for the generation and control of nonlinear chiral light in resonant optical systems. We reveal that nonlinear resonant generation of circularly polarized light from achiral dielectric metasurfaces is extremely sensitive to the polarization state of the fundamental wave, and a resonant metasurface can produce light with arbitrary degree of nonlinear chirality (DNC). Experimentally, we demonstrate that the chirality of nonlinear radiation from one metasurface can be continuously tuned from DNC = -0.86 to DNC = 0.94 by simply varying the polarization angle of the incident wave. By further exploiting the instantaneous polarization state, nonlinear chirality has been switched in a delay time step of 3.2 fs, which is orders of magnitude more sensitive than the current state-of-the-art polarization modulation. These results promise to enrich our understanding of nonlinear processes in chiral structures and their manipulation with resonant photonic structures.

physics.optics↗

arXiv2022

Giant superchiral field at merged bound states in the continuum

Superchiral field is highly important for ultrasensitive detection of chiral objects and has been intensively explored. Despite the progress, the construction of electromagnetic field in achiral nanostructures with giant chirality (C) is fundamentally restricted. Here, we demonstrate a novel approach to construct superchiral field in achiral dielectric metasurfaces. Due to the quantum spin-hall effect, each symmetry-protected bound state in the continuum (BIC) exhibits the ability to support a superchiral field in vicinity of Γpoint. By merging two BICs with orthogonal polarizations, all the criteria for a superchiral field are satisfied and the dramatic enhancement of chirality becomes more robust. Using typical photonic crystal slabs, we have produced a superchiral field with enhancement factor (C/C_CPL) orders of magnitude higher than state-of-the-art in nanostructures. By further introducing active chiral medium, a chiral mode splitting associated with giant enhancement of circular dichroism (CD) has been formed by the chiral light-matter interaction.

physics.optics↗