Amplification of nonlinear polariton pulses in waveguides.

Using a sub-millimeter exciton-polariton waveguide suitable for integrated photonics, we experimentally demonstrate nonlinear modulation of pico-Joule pulses at the same time as amplification sufficient to compensate the system losses. By comparison with a numerical model we explain the observed interplay of gain and nonlinearity as amplification of the interacting polariton field by stimulated scattering from an incoherent continuous-wave reservoir that is depleted by the pulses. This combination of gain and giant ultrafast nonlinearity operating on picosecond pulses has the potential to open up new directions in low-power all-optical information processing and nonlinear photonic simulation of conservative and driven-dissipative systems.

Spatiotemporal continuum generation in polariton waveguides.

We demonstrate the generation of a spatiotemporal optical continuum in a highly nonlinear exciton-polariton waveguide using extremely low excitation powers (2-ps, 100-W peak power pulses) and a submillimeter device suitable for integrated optics applications. We observe contributions from several mechanisms over a range of powers and demonstrate that the strong light-matter coupling significantly modifies the physics involved in all of them. The experimental data are well understood in combination with theoretical modeling.

Linearly polarized emission from an embedded quantum dot using nanowire morphology control.

GaAs nanowires with elongated cross sections are formed using a catalyst-free growth technique. This is achieved by patterning elongated nanoscale openings within a silicon dioxide growth mask on a (111)B GaAs substrate. It is observed that MOVPE-grown vertical nanowires with cross section elongated in the [21̅1̅] and [1̅12] directions remain faithful to the geometry of the openings.

Waveguide coupled resonance fluorescence from on-chip quantum emitter.

Resonantly driven quantum emitters offer a very promising route to obtain highly coherent sources of single photons required for applications in quantum information processing (QIP). Realizing this for on-chip scalable devices would be important for scientific advances and practical applications in the field of integrated quantum optics. Here we report on-chip quantum dot (QD) resonance fluorescence (RF) efficiently coupled into a single-mode waveguide, a key component of a photonic integrated circuit, with a negligible resonant laser background and show that the QD coherence is enhanced by more than a factor of 4 compared to off-resonant excitation.

Experimental investigation and numerical modelling of photocurrent oscillations in lattice matched Ga1-xInxNyAs1-y/GaAs quantum well p-i-n photodiodes.

Photocurrent oscillations, observed at low temperatures in lattice-matched Ga1-xInxNyAs1-y/GaAs multiple quantum well (MQW) p-i-n samples, are investigated as a function of applied bias and excitation wavelength and are modelled with the aid of semiconductor simulation software. The oscillations appear only at low temperatures and have the highest amplitude when the optical excitation energy is in resonance with the GaInNAs bandgap. They are explained in terms of electron accumulation and the formation of high-field domains in the GaInNAs QWs as a result of the disparity between the photoexcited electron and hole escape rates from the QWs.

Photoconductivity and photoluminescence under bias in GaInNAs/GaAs MQW p-i-n structures.

The low temperature photoluminescence under bias (PLb) and the photoconductivity (PC) of a p-i-n GaInNAs/GaAs multiple quantum well sample have been investigated. Under optical excitation with photons of energy greater than the GaAs bandgap, PC and PLb results show a number of step-like increases when the sample is reverse biased. The nature of these steps, which depends upon the temperature, exciting wavelength and intensity and the number of quantum wells (QWs) in the device, is explained in terms of thermionic emission and negative charge accumulation due to the low confinement of holes in GaInNAs QWs.