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We present a series of microdisk lasers realized within the same GaN-on-Si photonic platform scheme, and operating at room temperature under pulsed optical pumping over a broad spectral range extending over λ=275 nm-470 nm. The III-nitride microdisks embed either binary GaN/AlN multiple quantum wells (MQWs) for UV operation, or ternary InGaN/GaN MQWs for violet and blue operation. This demonstrates the versatility of this nitride-on-silicon platform, and the realization on this platform of efficient active layers for lasing action over a 200 nm broad UV to visible spectral range. We probe the lasing threshold carrier density over the whole spectral range and found that it is similar whatever the emission wavelength for these Q>1000 microdisk resonators with a constant material quality until quantum confined Stark effect takes over. The threshold is also found independent of microdisk diameters from 3 to 12 lm, with a β factor intermediate between the one of vertical cavity lasers and the one of small modal volume "thresholdless" lasers. [ABSTRACT FROM AUTHOR]

n-doped germanium can be used as an active material for the realization of an optical source under electrical pumping. We propose to use Schottky contacts for germanium electroluminescent devices, and we show that carrier injection and electroluminescence in these Schottky devices can be optimized by depositing a thin Al2O3 interfacial layer on top of n-doped germanium. In the latter case, hole injection is optimized due to the drastic decrease of interface trap densities and room-temperature electroluminescence can be observed at small current injection with a higher differential efficiency as compared to the standard Schottky sample. [ABSTRACT FROM AUTHOR]

Lasing of triangular and square lattice photonic crystal, waveguides on InP substrate is investigated around the 1.5-μm wavelength by optical pumping. The lattice period of the fabricated structures is varied over a very large scale, thereby allowing a detailed exploration of the laser behaviors in the cases of micrometer width waveguides. A genuine distributed feedback (DFB) laser emission is observed in the gap for W2-3 waveguides in the ΓM direction of a triangular lattice. A different behavior is obtained for W3 waveguides in the ΓK direction of the same lattice as well as for W1 and W3 waveguides in the ΓX direction of a square lattice. The laser emission is found to occur at the Γ point of the Brillouin zone (wavevector k=0) when the emission frequency is outside the gap. The DFB-like laser emission is intrinsically single mode in this case. Plane wave calculations show that the field distributions of the two DFB components are radically different. The emitting mode is well localized in the guide core while the non-lasing mode spreads over the whole crystal. [ABSTRACT FROM PUBLISHER]

We show that quantum dot intersublevel transitions can be coupled to midinfrared photonic crystal modes. The coupling is observed under optical pumping with S-P intersublevel transitions of InGaAs self-assembled quantum dots resonant around 20 μm wavelength. An enhancement in the intersublevel absorption and a spectral tuning are evidenced when the optical modes of two-dimensional photonic crystals enter in resonance with the photoinduced intersublevel absorption. This effect is illustrated in the case of GaAs two-dimensional photonic crystal membranes with lattice periodicities of 10.5, 9.5, and 8.5 μm containing multilayers of self-assembled quantum dots. [ABSTRACT FROM AUTHOR]