The physics behind nonlinear propagation of picosecond pulses in micro‐ and nano‐wire single mode waveguides either grown by chemical vapor deposition or etched into semiconductor microresonators are reviewed. If operated in the strong coupling regime exciton‐polaritons form in those wires and a highly nonlinear platform is established interfacing optical, condensed matter, quantum, and statistical physics. A theory of the exciton‐polariton pulse compression, pulse breaking, and emission of the backward Cherenkov radiation have been developed. This highly nonlinear dynamics is associated with the relaxation of the exciton‐polariton spectrum down to low momenta, mediated solely by the exciton–exciton scattering. Such nonlinearity‐enhanced thermalization results in a phase transition from propagating exciton‐polariton pulses toward the formation of a non‐equilibrium polariton condensate in the microwire system.

We present a model to describe the spatiotemporal evolution of guided modes in semiconductor nanowires based on a coupled mode formalism. Light-matter interaction is modelled based on semiconductor Bloch equations, including many-particle effects in the screened Hartree-Fock approximation. Appropriate boundary conditions are used to incorporate reflections at waveguide endfacets, thus allowing for the simulation of nanowire lasing. We compute the emission characteristics and temporal dynamics of CdS and ZnO nanowire lasers and compare our results both to Finite-Difference Time-Domain simulations and to experimental data. Finally, we explore the dependence of the lasing emission on the nanowire cavity and on the materials relaxation time.

Coherent light sources confining the light below the vacuum wavelength barrier will drive future concepts of nanosensing, nanospectroscopy, and photonic circuits. Here, we directly image the angular emission of such a light source based on single semiconductor nanowire lasers. It is confirmed that the lasing switches from the fundamental mode in a thin ZnO nanowire to an admixture of several transverse modes in thicker nanowires approximately at the multimode cutoff. The mode competition with higher order modes substantially slows down the laser dynamics. We show that efficient photonic mode filtering in tapered nanowires selects the desired fundamental mode for lasing with improved performance including power, efficiency, and directionality important for an optimal coupling between adjacent nanophotonic waveguides.

We present a high quality two-dimensional cavity structure based on ZnO nanowires coated with concentrical Bragg reflectors. The spatial mode distribution leads to the simultaneous appearance of the weak and strong coupling regime even at room temperature. Photoluminescence (PL) measurements agree with finite difference time domain (FDTD) simulations. Furthermore the ZnO core nanowires allow for the observation of middle polariton branches between the A- and B-exciton ground state resonances. Further, lasing emission up to room temperature is detected in excitation dependent photoluminescence measurements.

We present a time-domain model for the simulation of light-matter interaction in semiconductors in arbitrary geometries and across a wide range of excitation conditions. The electromagnetic field is treated classically using the finite-difference time-domain method. The polarization and occupation numbers of the semiconductor material are described using the semiconductor Bloch equations including many-body effects in the screened Hartree-Fock approximation. Spontaneous emission noise is introduced using stochastic driving terms. As an application of the model, we present simulations of the dynamics of a nanowire laser including optical pumping, seeding by spontaneous emission and the selection of lasing modes.

FIG. 5. (Color online) Spatiotemporal field dynamics inside a nanowire laser (l = 7.5 μm, d = 250 nm). (a) and (d) Electric field intensity in an xz and an xy slice of the simulation volume during pumping. (b) |E|2 averaged across transverse slices and plotted along z and t . (e)–(g) Transverse intensity profiles inside the wire during lasing emission. (c) Intensity profile in an xz slice after the maximum of the lasing emission.

We use finite-difference time-domain modeling to investigate plasma generation induced by multiphoton absorption of intense laser light in dielectrics with tiny inhomogeneities. Plasma generation is found to be strongly amplified around nanometer-sized inhomogeneities as present in glasses. Each inhomogeneity acts as the seed of a plasma structure growing against the direction of light propagation. Plasma structures originating from randomly distributed inhomogeneities are found to interact strongly and to organize in regularly spaced planes oriented perpendicularly to the laser polarization. We discuss similarities between our results and nanogratings in fused silica written by laser beams with spatially homogeneous as well as radial and azimuthal polarizations.

High quality CdS nanowires suspended in air were optically pumped both below and above the lasing threshold. The polarization of the pump laser was varied while emission out of the end facet of the nanowire was monitored in a 'head-on' measurement geometry. Highest pump-efficiency and most efficient absorption of the pump radiation are demonstrated for an incident electric field being polarized parallel to the nanowire axis. This polarization dependence, which was observed both above the lasing threshold and in the regime of amplified spontaneous emission, is caused by an enhanced absorption for parallel polarized optical pumping. Measured Stokes parameters of the nanowire emission reveal that due to the onset of lasing the degree of polarization rapidly increases from approximately 15% to 85%. Both, Stokes parameters and degree of polarization of the nanowire lasing emission are independent of the excitation polarization. The transversal lasing mode is therefore not notably affected by the polarization of the pumping beam, although the supply with optical gain is significantly enhanced for an excitation polarization parallel to the nanowire axis.

Tin-doped cadmium sulfide nanowires reveal donor-acceptor pair transitions at low-temperature photoluminescence and furthermore exhibit ideal resonator morphology appropriate for lasing at continuous wave pumping. The continuous wave lasing mode is proven by the evolution of the emitted power and spectrum with increasing pump intensity. The high temperature stability up to 120 K at given pumping power is determined by the decreasing optical gain necessary for lasing in an electron-hole plasma.