The Lorenz model for single-mode homogeneously broadened laser: analytical determination of the unpredictible zone

We have applied harmonic expansion to derive an analytical solution for the Lorenz-Haken equations. This method is used to describe the regular and periodic self-pulsing regime of the single mode homogeneously broadened laser. These periodic solutions emerge when the ratio of the population decay rates is smaller than 0.11. We have also demonstrated the tendency of the Lorenz-Haken dissipative system to behave periodic for a characteristic pumping rate "2CP" [4], close to the second laser threshold "2C2th" (threshold of instability). When the pumping parameter "2C" increases, the laser undergoes a period-doubling sequence. This cascade of period doubling leads towards chaos. We study this type of solutions and indicate the zone of the control parameters for which the system undergoes irregular pulsing solutions. We had previously applied this analytical procedure to derive the amplitude of the first, third and the fifth order harmonics for the laser-field expansion [4, 14]. In this work, we extend this method in the aim of obtaining the higher harmonics. We show that this iterative method is indeed limited to the fifth order, and that above, the obtained analytical solution diverges from the numerical direct resolution of the equations.Comment: 20 pages, 4 figures, 1 anne

Kindling molecules: a new way to ‘break’ the Abbe limit

International audienceFluorescence microscopy is a key tool for biological investigations. However, compared to other techniques like electron microscopy, the achievable resolution is still limited. Tremendous efforts have been devoted to improve the resolution of far-field optical microscopy. Several techniques do exist; however their adoption by biologists has been slowed by several technical limitations. We propose a new method based on a recently discovered family of optically switchable fluorescent molecules. Kindling proteins open the way to very high resolution in far-field fluorescence 3-D microscopy with relatively simple techniques

Multi-kernel deconvolution applied to confocal fluorescence microscopy with engineered point spread function

Fluorescence microscopy is a powerful technique in biology, because of the immense variety of markers now available. Compared to other methods, its resolution is however limited. In wide-field microscopy, the technique of structured illumination permits to improve the lateral resolution by a factor of two, even surpassing confocal microscopy, which permits a theoretical gain of about 40%. We propose an alternate technique, combining laterally interfering focused beams, which should permit the same gain of resolution in a confocal microscope. Furthermore, this technique, combined with multiple acquisition and multikernel deconvolution, permits a better object reconstruction than classical monokernel deconvolution using a regular excitation point spread function

Polarized confocal theta microscopy

International audienceWe propose a comprehensive treatment of theta microscopy based on dipole emission, which better describes fluorescence emission than the isotropic emission model, as fluorescence emission is often polarized. Formulas describing the point spread function for polarized confocal fluorescence theta microscopy are given. Examples are given and some advantages of polarized theta fluorescence microscopy are presented

Photonic Gap Antennas Based on High Index-Contrast Slot-Waveguides

Optical antennas made of low-loss dielectrics have several advantages over plasmonic antennas, including high radiative quantum efficiency, negligible heating and excellent photostability. However, due to weak spatial confinement, conventional dielectric antennas fail to offer light-matter interaction strengths on par with those of plasmonic antennas. We propose here an all-dielectric antenna configuration that can support strongly confined modes ($V\sim10^{-4}\lambda_{0}^3$) while maintaining unity antenna quantum efficiency. This configuration consists of a high-index pillar structure with a transverse gap that is filled with a low-index material, where the contrast of indices induces a strong enhancement of the electric field perpendicular to the gap. We provide a detailed explanation of the operation principle of such Photonic Gap Antennas (PGAs) based on the dispersion relation of symmetric and asymmetric horizontal slot-waveguides. To discuss the properties of PGAs, we consider silicon pillars with air or CYTOP as the gap-material. We show by full-wave simulations that PGAs with an emitter embedded in the gap can enhance the spontaneous emission rate by a factor of $\sim$1000 for air gaps and $\sim$400 for CYTOP gaps over a spectral bandwidth of $\Delta\lambda\approx300$ nm at $\lambda=1.25$ \textmu m. Furthermore, the PGAs can be designed to provide unidirectional out-of-plane radiation across a substantial portion of their spectral bandwidth. This is achieved by setting the position of the gap at an optimized off-centered position of the pillar so as to properly break the vertical symmetry of the structure. We also demonstrate that, when acting as receivers, PGAs can lead to a near-field intensity enhancement by a factor of $\sim$3000 for air gaps and $\sim$1200 for CYTOP gaps

Hybrid Epsilon-Near-Zero Modes of Photonic Gap Antennas

We demonstrate that in photonic gap antennas composed of an epsilon-near-zero (ENZ) layer embedded within a high-index dielectric, hybrid modes emerge from the strong coupling between the ENZ thin film and the photonic modes of the dielectric antenna. These hybrid modes show giant electric field enhancements, large enhancements of the far-field spontaneous emission rate and a unidirectional radiation response. We analyze both parent and hybrid modes using quasinormal mode theory and find that the hybridization can be well understood using a coupled oscillator model. Under plane wave illumination, hybrid ENZ antennas can concentrate light with an electric field amplitude $\sim$100 times higher than that of the incident wave, which places them on par with the best plasmonic antennas. In addition, the far-field spontaneous emission rate of a dipole embedded at the antenna hotspot reaches up to $\sim$2300 that in free space, with nearly perfect unidirectional emission.Comment: 5 figures, 6 page

Halide perovskites enable polaritonic \u3ci\u3eXY\u3c/i\u3e spin Hamiltonian at room temperature

Exciton polaritons, the part-light and part-matter quasiparticles in semiconductor optical cavities, are promising for exploring Bose–Einstein condensation, non-equilibrium many-body physics and analogue simulation at elevated temperatures. However, a room-temperature polaritonic platform on par with the GaAs quantum wells grown by molecular beam epitaxy at low temperatures remains elusive. The operation of such a platform calls for long-lifetime, strongly interacting excitons in a stringent material system with large yet nanoscale-thin geometry and homogeneous properties. Here, we address this challenge by adopting a method based on the solution synthesis of excitonic halide perovskites grown under nanoconfinement. Such nanoconfinement growth facilitates the synthesis of smooth and homogeneous single-crystalline large crystals enabling the demonstration of XY Hamiltonian lattices with sizes up to 10 × 10. With this demonstration, we further establish perovskites as a promising platform for room temperature polaritonic physics and pave the way for the realization of robust mode-disorder-free polaritonic devices at room temperature

Isotropic-Resolution Tomographic Diffractive Microscopy

International audienceMicroscopy techniques based on recording of the optical field diffracted by the specimen, in amplitude and phase, like Digital Holographic Microscopy (DHM) have been a growing research topic in recent years. Tomographic acquisitions are possible if one is able to record information, while controlling variations of the specimen illumination. Classical approaches consider either illumination variation, simple to implement, but suffering fro the classical "missing cone" problem, or sample rotation, delivering images with quasi-isotropic, but lower resolution. We have developed an original-, combined tomographic diffractive microscope setup, making use of specimen rotation as well as illumination rotation, which is able to deliver images with an almost isotropic resolution better than 200 nm