Higher-order optical harmonics entered the realm of nanostructured solids being observed recently in optical gratings and metasurfaces with a subwavelength thickness. Structuring materials at the subwavelength scale allows us toresonantly enhance the efficiency of nonlinear processes and reduce the size of high-harmonic sources. We report the observation of up to a seventh harmonic generated from a single subwavelength resonator made of AlGaAs material. This process is enabled by careful engineering of the resonator geometry for supporting an optical mode associated with a quasi-bound state in the continuum in the mid-infrared spectral range at around λ = 3.7 μm pump wavelength. The resonator volume measures ~0.1 λ. The resonant modes are excited with an azimuthally polarized tightly focused beam. We evaluate the contributions of perturbative and nonperturbative nonlinearities to the harmonic generation process. Our work proves the possibility to miniaturize solid-state sources of high harmonics to the subwavelength volumes.
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http://dx.doi.org/10.1126/sciadv.adg2655 | DOI Listing |
Sci Rep
December 2024
Department of Electronics, Carleton University, Ottawa, ON, K1S 5B6, Canada.
In this paper, we propose a novel structure of anisotropic graphene-based hyperbolic metamaterial (AGHMM) sandwiched as a defect between two one-dimensional photonic crystals (PCs) in the terahertz (THz) region. The proposed structure is numerically simulated and analyzed using the transfer matrix method, effective medium theory and three-dimensional finite-difference time-domain. The defect layer of AGHMM consists of graphene sheets separated by subwavelength dielectric spacers.
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December 2024
Physical Research Laboratory, Ahmedabad, Gujarat, 380009, India.
Talbot length, the distance between two consecutive self-image planes along the propagation axis for a periodic diffraction object (grating) illuminated by a plane wave, depends on the period of the object and the wavelength of illumination. This property makes the Talbot effect a straightforward technique for measuring the period of a periodic object (grating) by accurately determining the Talbot length for a given illumination wavelength. However, since the Talbot length scale is proportional to the square of the grating period, traditional Talbot techniques face challenges when dealing with smaller grating periods and minor changes in the grating period.
View Article and Find Full Text PDFAdv Mater
December 2024
School of Nano-Tech and Nano-Bionics, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China.
Monolayer transition metal dichalcogenides (TMDs) with strong exciton effects have enabled diverse light emitting devices, however, their Ångstrom thickness makes it challenging to efficiently manipulate exciton emission by themselves. Although their nanostructured multi-layer counterparts can effectively manipulate optical field at deep subwavelength thickness scale, these indirect band gap multi-layer TMDs are lack of strong luminescence, hindering their applications in light emitting devices. Here, the integration of monolayer TMDs is presented with nanostructured multi-layer TMDs, combining both strong exciton emission and optical manipulation in a single ultra-thin platform.
View Article and Find Full Text PDFInverse design (ID) is a computational method that systematically explores a design space to find optimal device geometries based on specific performance criteria. In silicon photonics, ID often generates design features that degrade significantly due to the fabrication process, limiting the applicability of these devices in scalable fabrication. We demonstrate a solution to this performance degradation through fabrication-aware inverse design (FAID), integrating lithography models for deep-ultraviolet (DUV) lithography and electron-beam lithography (EBL) into the shape optimization approach of ID.
View Article and Find Full Text PDFPhys Rev Lett
December 2024
JILA, NIST, Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
We investigate the driven-dissipative dynamics of multilevel atomic arrays interacting via dipolar interactions at subwavelength spacings. Unlike two-level atoms in the weakly excited regime, multilevel atoms can become strongly entangled. The entanglement manifests as the growth of spin waves in the ground-state manifold and survives after turning off the drive.
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