A monolithic compound semiconductor phototransducer optimized for narrow-band light sources was designed for and has achieved conversion efficiencies exceeding 50%. The III-V heterostructure was grown by MOCVD, based on the vertical stacking of a number of partially absorbing GaAs n/p junctions connected in series with tunnel junctions. The thicknesses of the p-type base layers of the diodes were engineered for optimal absorption and current matching for an optical input with wavelengths centered in the 830 nm to 850 nm range. The device architecture allows for improved open-circuit voltage in the individual base segments due to efficient carrier extraction while simultaneously maintaining a complete absorption of the input photons with no need for complicated fabrication processes or reflecting layers. Progress for device outputs achieving in excess of 12 V is reviewed in this study.
We study the dynamics of the interaction between two weak light beams mediated by a strongly coupled quantum dot-photonic crystal cavity system. We demonstrate switching between two weak pulsed beams (40 ps pulses), observing an increase of the systems transmission when the signal and the control pulses overlap inside the cavity. Our results show that the quantum dot-nanocavity system enables fast, controllable optical switching at the single-photon level.
Cold atoms confined inside a hollow-core photonic-crystal fiber with core diameters of a few photon wavelengths
are a promising medium for studying nonlinear optical interactions at extremely low light levels. The high electric
field intensity per photon and interaction lengths not limited by diffraction are some of the unique features of
this system. Here, we present the results of our first nonlinear optics experiments in this system including a
demonstration of an all-optical switch that is activated at energies corresponding to few hundred optical photons