In this work, we report InGaAs based photodiodes integrating liquid crystal (LC) microcells resonant microcavity on their surface. The LC microcavities monolithically integrated on the photodiodes act as a wavelength selective filter for the device. Photodetection measurements performed with a tunable laser operating in the telecom S and C bands demonstrated a wavelength sweep for the photodiode from 1480 nm to 1560 nm limited by the tuning range of the laser. This spectral window is covered with a LC driving voltage of 7V only, corresponding to extremely low power consumption. The average sensitivity over the whole spectral range is 0.4 A/W, slightly lower than 0.6 A/W for similar photodiodes that do not integrate such a LC tunable filter. The quality of the filter integrated onto the surfaces of the photodiodes is constant over a large tuning range (70 nm), showing a FWHM of 1.5 nm.
InAs nanostructures formed on InP substrates allow the realization of devices working in telecommunication wavelength range between 1.4 and 1.65 μm. However due to the low lattice mismatch existing between InAs and InP, the self assembling process in InP is more complex than on GaAs substrates. First high density quantum wires obtained on InP(001) have been integrated in laser. Lasers emitting at room
temperature have been achieved. For an infinite length cavity, a threshold current density per QD plane as low as 45 A/cm<sup>2</sup> is deduced. This result compares favourably with those obtained on quantum wells lasers. However, the stability of the threshold current with temperature, predicted for quantum dots laser is not
observed. Thus, growth on non standard substrates such as miscut substrates or high index substrates have been investigated in order to achieve QDs on InP. On (113) B substrates, quantum dots in high density and with size comparable with those achieved on GaAs(001) have been obtained. Lasers with record threshold current have been obtained. However the modulation properties of the laser are not as good as predicted for ideal quantum dots lasers. Finally we present the attempts to extend the QD emission wavelength in the 2-3
We report on light scattering experiments (Raman-Brillouin) in semiconductor quantum wells and quantum dots nanostructures. All measurements were performed under resonant excitation of the optical transitions involving confined electronic states. The scattered light was detected in the very low-frequency range around the Rayleigh line. We observe strong oscillations of the scattered intensity. Their period and relative amplitudes depend on the sample characteristics (size, density and spatial distribution of nano-objects). We show that such signal originates from interference effects due to the interaction between sound waves and the excited electronic density. By comparing simulated and measured spectra, we are able to extract, from the experiments, sample characteristics such as average size and size distribution of quantum dots. This optical sensing technique, namely Raman interferometry, is similar to the well-known X-ray diffraction technique, in the sense that it allows imaging of electronic states in the reciprocal space. Moreover, we show that Raman interferometry is a surface sensitive technique. By using quantum dots and quantum wells as Thz acoustic-detectors we are able to measure the reflection of sound waves at the sample surface. The surface characteristics (nano-scale roughness and oxidation) can be addressed using this method.