Nonlinear Polariton Fluids in a Flatband Reveal Discrete Gap Solitons

Phase frustration in periodic lattices is responsible for the formation of dispersionless flat bands. The absence of any kinetic energy scale makes flat band physics critically sensitive to perturbations and interactions. We report here on the experimental investigation of the nonlinear dynamics of cavity polaritons in the gapped flat band of a one-dimensional Lieb lattice. We observe the formation of gap solitons with quantized size and very abrupt edges, signature of the frozen propagation of switching fronts. This type of gap solitons belongs to the class of truncated Bloch waves, and had only been observed in closed systems up to now. Here the driven-dissipative character of the system gives rise to a complex multistability of the nonlinear domains generated in the flat band. These results open up interesting perspective regarding more complex 2D lattices and the generation of correlated photon phases.Comment: 6 pages, 4 figures + supplemental material (6 pages, 6 figures

Verification and application of multi-source focus quantification

International audienceThe concept of the multi-source focus correlation method was presented in 2015 [1, 2]. A more accurate understanding of real on-product focus can be obtained by gathering information from different sectors: design, scanner short loop monitoring, scanner leveling, on-product focus and topography. This work will show that chip topography can be predicted from reticle density and perimeter density data, including experimental proof.Different pixel sizes are used to perform the correlation in-line with the minimum resolution, correlation length of CMP effects and the spot size of the scanner level sensor.Potential applications of the topography determination will be evaluated, includingoptimizing scanner leveling by ignoring non-critical parts of the field, and without the need for time-consuming offline topography measurements

Measuring topological invariants in polaritonic graphene

Topological materials rely on engineering global properties of their bulk energy bands called topological invariants. These invariants, usually defined over the entire Brillouin zone, are related to the existence of protected edge states. However, for an important class of Hamiltonians corresponding to 2D lattices with time-reversal and chiral symmetry (e.g. graphene), the existence of edge states is linked to invariants that are not defined over the full 2D Brillouin zone, but on reduced 1D sub-spaces. Here, we demonstrate a novel scheme based on a combined real- and momentum-space measurement to directly access these 1D topological invariants in lattices of semiconductor microcavities confining exciton-polaritons. We extract these invariants in arrays emulating the physics of regular and critically compressed graphene sucht that Dirac cones have merged. Our scheme provides a direct evidence of the bulk-edge correspondence in these systems, and opens the door to the exploration of more complex topological effects, for example involving disorder and interactions.Comment: Suppl. Mat. added; improved data/error analysi

Reconfigurable photon localization by coherent drive and dissipation in photonic lattices

7 pags., 4 figs.The engineering of localized modes in photonic structures is one of the main targets of modern photonics. An efficient strategy to design these modes is to use the interplay of constructive and destructive interference in periodic photonic lattices. This mechanism is at the origin of the defect modes in photonic bandgaps, bound states in the continuum, and compact localized states in flat bands. Here, we show that in lattices of lossy resonators, the addition of external optical drives with a controlled phase enlarges the possibilities of manipulating interference effects and allows for the design of novel types of localized modes. Using a honeycomb lattice of coupled micropillars resonantly driven with several laser spots at energies within its photonic bands, we demonstrate the localization of light in at-will geometries down to a single site. These localized modes are fully reconfigurable and have the potentiality of enhancing nonlinear effects and of controlling light-matter interactions with single site resolution.Ministerio de Ciencia, Innovación y Universidades (PGC2018-094792-B-100); Consejo Superior de Investigaciones Científicas (PTI-001); Comunidad de Madrid (CAM 2020 Y2020/TCS-6545); Narodowe Centrum Nauki (DEC-2019/32/T/ST3/00332); Agence Nationale de la Recherche (ANR-11-LABX-0007, ANR-16-CE30-0021, ANR-16-IDEX-0004 ULNE, ANR-QUAN-0003-05); European Research Council (820392, 865151, 949730), Région Hauts-de-France

Continuous-Wave Second-Harmonic Generation in Orientation-Patterned Gallium Phosphide Waveguides at Telecom Wavelengths

A new process to produce orientation-patterned gallium phosphide (OP-GaP) on GaAs with almost perfectly parallel domain boundaries is presented. Taking advantage of the chemical selectivity between phosphides and arsenides, OP-GaP is processed into suspended shallow-ridge waveguides. Efficient second-harmonic generation from telecom wavelengths is achieved in both Type-I and Type-II polarisation configurations. The highest observed conversion efficiency is 200% W–1 cm–2, with a bandwidth of 2.67 nm in a 1 mm-long waveguide. The variation of the conversion efficiency with wavelength closely follows a squared cardinal sine function, in excellent agreement with theory, confirming the good uniformity of the poling period over the entire length of the waveguide

Topological gap solitons in a 1D non-Hermitian lattice

Nonlinear topological photonics is an emerging field aiming at extending the fascinating properties of topological states to the realm where interactions between the system constituents cannot be neglected. Interactions can indeed trigger topological phase transitions, induce symmetry protection and robustness properties for the many-body system. Moreover when coupling to the environment via drive and dissipation is also considered, novel collective phenomena are expected to emerge. Here, we report the nonlinear response of a polariton lattice implementing a non-Hermitian version of the Su-Schrieffer-Heeger model. We trigger the formation of solitons in the topological gap of the band structure, and show that these solitons demonstrate robust nonlinear properties with respect to defects, because of the underlying sub-lattice symmetry. Leveraging on the system non-Hermiticity, we engineer the drive phase pattern and unveil bulk solitons that have no counterpart in conservative systems. They are localized on a single sub-lattice with a spatial profile alike a topological edge state. Our results demonstrate a tool to stabilize the nonlinear response of driven dissipative topological systems, which may constitute a powerful resource for nonlinear topological photonics

Fast spectrally encoded Mueller optical scanning microscopy

Mueller microscopes enable imaging of the optical anisotropic properties of biological or non-biological samples, in phase and amplitude, at sub-micrometre scale. However, the development of Mueller microscopes poses an instrumental challenge: the production of polarimetric parameters must be sufficiently quick to ensure fast imaging, so that the evolution of these parameters can be visualised in real-time, allowing the operator to adjust the microscope while constantly monitoring them. In this report, a full Mueller scanning microscope based on spectral encoding of polarization is presented. The spectrum, collected every 10 μs for each position of the optical beam on the specimen, incorporates all the information needed to produce the full Mueller matrix, which allows simultaneous display of all the polarimetric parameters, at the unequalled rate of 1.5 Hz (for an image of 256 × 256 pixels). The design of the optical blocks allows for the real-time display of linear birefringent images which serve as guidance for the operator. In addition, the instrument has the capability to easily switch its functionality from a Mueller to a Second Harmonic Generation (SHG) microscope, providing a pixel-to-pixel matching of the images produced by the two modalities. The device performance is illustrated by imaging various unstained biological specimens

Advanced metrology by offline SEM data processing

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