Tracking exceptional points above the lasing threshold.

Recent studies on exceptional points (EPs) in non-Hermitian optical systems have revealed unique traits, including unidirectional invisibility, chiral mode switching and laser self-termination. In systems featuring gain/loss components, EPs are commonly accessed below the lasing threshold, i.e.

Spontaneous Symmetry Breaking in a Coherently Driven Nanophotonic Bose-Hubbard Dimer.

We report on the first experimental observation of spontaneous mirror symmetry breaking (SSB) in coherently driven-dissipative coupled optical cavities. SSB is observed as the breaking of the spatial or mirror Z_{2} symmetry between two symmetrically pumped and evanescently coupled photonic crystal nanocavities, and manifests itself as random intensity localization in one of the two cavities. We show that, in a system featuring repulsive boson interactions (U>0), the observation of a pure pitchfork bifurcation requires negative photon hopping energies (J<0), which we have realized in our photonic crystal molecule.

Experimental study of speckle patterns generated by low-coherence semiconductor laser light.

Speckle is a wave interference phenomenon that has been studied in various fields, including optics, hydrodynamics, and acoustics. Speckle patterns contain spectral information of the interfering waves and of the scattering medium that generates the pattern. Here, we study experimentally the speckle patterns generated by the light emitted by two types of semiconductor lasers: conventional laser diodes, where we induce low-coherence emission by optical feedback or by pump current modulation, and coupled nanolasers.

Mesoscopic Limit Cycles in Coupled Nanolasers.

Two coupled nanolasers exhibit a mode switching transition, theoretically described by mode beating limit cycle oscillations. Their decay rate is vanishingly small in the thermodynamic limit, i.e.

Metasurface-based total internal reflection microscopy.

Recent years have seen a tremendous progress in the development of dielectric metasurfaces for visible light applications. Such metasurfaces are ultra-thin optical devices that can manipulate optical wavefronts in an arbitrary manner. Here, we present a newly developed metasurface which allows for coupling light into a microscopy coverslip to achieve total internal reflection (TIR) excitation.

Strong Coupling between Self-Assembled Molecules and Surface Plasmon Polaritons.

We experimentally demonstrate strong coupling between self-assembled PTCDI-C7 organic molecules and the electromagnetic mode generated by surface plasmon polaritons (SPPs). The system consists of a dense self-assembly of ordered molecules evaporated directly on a thin gold film, which stack perpendicularly to the metal surface to form H-aggregates, without a host matrix. Experimental wavevector-resolved reflectance spectra show the formation of hybrid states that display a clear anticrossing, attesting the strong coupling regime with a Rabi splitting energy of Ω ≃ 102 meV at room temperature.

Asymmetric mode scattering in strongly coupled photonic crystal nanolasers.

We investigate the basic mechanism of nonlinear mode competition in two semiconductor-coupled nanocavities operating in the laser regime. For this, we study energy transfer between bonding (in-phase) and anti-bonding (out-of-phase) modes of the system formed by two strongly coupled photonic crystal nanolasers. We experimentally observe mode switching from the blue-detuned to the red-detuned mode as the pump power is increased.

Millisecond Photon Lifetime in a Slow-Light Microcavity.

Optical microcavities with ultralong photon storage times are of central importance for integrated nanophotonics. To date, record quality (Q) factors up to 10^{11} have been measured in millimetric-size single-crystal whispering-gallery-mode (WGM) resonators, and 10^{10} in silica or glass microresonators. We show that, by introducing slow-light effects in an active WGM microresonator, it is possible to enhance the photon lifetime by several orders of magnitude, thus circumventing both fabrication imperfections and residual absorption.

Improving image contrast in fluorescence microscopy with nanostructured substrates.

Metallic and dielectric nanostructures can show sharp contrasted resonances, sensitive to the environment, and high field enhancement in sub-wavelength volumes. For this reason, these structures are commonly used as molecular sensors. Only few works have focused on their application in optical microscopy, in particular in superresolution.

Photonic molecules: tailoring the coupling strength and sign.

We demonstrate a large tuning of the coupling strength in Photonic Crystal molecules without changing the inter-cavity distance. The key element for the design is the "photonic barrier engineering", where the "potential barrier" is formed by the air-holes in between the two cavities. This consists in changing the hole radius of the central row in the barrier.

Coupling light into a slow-light photonic-crystal waveguide from a free-space normally-incident beam.

We present a coupler design allowing normally-incident light coupling from free-space into a monomode photonic crystal waveguide operating in the slow-light regime. Numerical three-dimensional calculations show that extraction efficiencies as high as 80% can be achieved for very large group indices up to 100. We demonstrate experimentally the device feasibility by coupling and extracting light from a photonic crystal waveguide over a large group-index range (from 10 to 60).

Enhancement of a nano cavity lifetime by induced slow light and nonlinear dispersions.

We start from a 2D photonic crystal nanocavity with moderate Q-factor and dynamically increase it by two order of magnitude by the joint action of coherent population oscillations and nonlinear refractive index.

High quality beaming and efficient free-space coupling in L3 photonic crystal active nanocavities.

We report on far-field measurements of L3 photonic crystal (PhC) cavities with high quality beaming. This is achieved by means of the so-called "band folding" technique, in which a modulation of the radius of specific holes surrounding the cavity is introduced. Far-field patterns are measured from photoluminescence of quantum wells embedded in the PhC.

Nanocavity linewidth narrowing and group delay enhancement by slow light propagation and nonlinear effects.

Slow light induced by coherent population oscillations and cavity dispersive nonlinear response are combined achieving 2 orders of magnitude enhancement of the group delay and an equivalent decreasing of the spectral linewidth of a L3 two-dimensional photonic crystal nanocavity.

Small volume excitation and enhancement of dye fluorescence on a 2D photonic crystal surface.

We demonstrate an easy-to-implement scheme for fluorescence enhancement and observation volume reduction using photonic crystals (PhCs) as substrates for microscopy. By normal incidence coupling to slow 2D-PhC guided modes, a 65 fold enhancement in the excitation is achieved in the near field region (100 nm deep and 1 microm wide) of the resonant mode. Such large enhancement together with the high spatial resolution makes this device an excellent substrate for fluorescence microscopies.

Thermo-optical dynamics in an optically pumped Photonic Crystal nano-cavity.

Linear and non-linear thermo-optical dynamical regimes were investigated in a photonic crystal cavity. First, we have measured the thermal relaxation time in an InP-based nano-cavity with quantum dots in the presence of optical pumping. The experimental method presented here allows one to obtain the dynamics of temperature in a nanocavity based on reflectivity measurements of a cw probe beam coupled through an adiabatically tapered fiber.

Dynamics of band-edge photonic crystal lasers.

Band-edge photonic crystal lasers were fabricated and their temporal characteristics were minutely analyzed using a high resolution up-conversion system. The InGaAs/InP photonic crystal laser operates at room temperature at 1.55 microm with turn on time ranging from 17ps to 30ps.

Continuous-wave operation of photonic band-edge laser near 1.55 microm on silicon wafer.

We report on the continuous-wave operation of a band edge laser at room temperature near 1.55 mum in an InGaAs/InP photonic crystal. A flat dispersion band-edge photonic mode is used for surface normal operation.

Fast thermo-optical excitability in a two-dimensional photonic crystal.

We experimentally demonstrate excitability in a semiconductor two-dimensional photonic crystal. Excitability is a nonlinear dynamical mechanism underlying pulselike responses to small perturbations in systems possessing one stable state. We show that a band-edge photonic crystal resonator exhibits class II excitability, resulting from the nonlinear coupling between the high-Q optical mode, the charge-carrier density, and the fast (sub-micros) thermal dynamics.

Nonadiabatic dynamics of the electromagnetic field and charge carriers in high-Q photonic crystal resonators.

We address, both experimentally and theoretically, phase and amplitude dynamics of the electromagnetic field in a two-dimensional photonic crystal when femtosecond pulses are injected. We demonstrate that the usual adiabatic approximation underlying the dynamics of field and carriers in a semiconductor resonator is no longer valid, since in general the photon lifetime cannot be neglected with respect to the carrier recombination lifetime. Parameter regions where adiabaticity is broken are shown, and the ubiquity of the observed dynamical scenario in the new generation of active photonic microresonators is predicted.

Coupled optical excitable cells.

In this work we investigate experimentally the dynamics of two coupled optical excitable cells, namely, two semiconductor lasers with optical feedback. We analyze the dynamics observed in terms of the statistical properties of the time series and in terms of the phase space reconstruction from the data. We build a model based on a simple set of deterministic equations (on a two torus) plus noise in order to capture the essential features of the dynamics observed.