1.5 µm Quantum Dots Spectral Hole Burning experiments for dual frequency laser engineering

International audienceThe Terahertz (THz) frequency domain is attractive for numerous applications including phonon spectroscopy, radio-astronomy, imaging, sensing and communication. Nevertheless the development of a compact, tunable, electrically driven room-temperature source operating in the THz band frequency [1-5 THz] remains a challenge. An alternative to low-temperature-cooled Quantum Cascade Lasers is the widely investigated photomixing technique which relies on semiconductor antenna fed by two laser fields beating at the targeted THz frequency. When a highly coherent CW emission is mandatory, a single laser cavity sustaining the oscillation of the two required laser fields is a very attractive approach. Indeed, the phase noises of the two optical fields being inherently correlated, the beatnote exhibits a high spectral purity. Following this paradigm, dual-frequency Quantum Wells (QWs) based Vertical External Cavity Surface Emitting Lasers (VECSELs) architectures have been successfully demonstrated [1][2][3]. Nevertheless, because of the inherent homogeneously broadened gain of QWs, the two laser modes suffer from strong coupling making it necessary to lift the spatial degeneracy inside the active medium. Moreover, the frequency detuning remains lower than in Quantum Dots (QDs). Accordingly, we have been exploring over the past years the benefits of using wider and potentially less homogeneously broadened gain medium such as Quantum Dots. To this aim, InAs QDs are grown on InP (311B) substrate, and characterized by photoluminescence and atomic force microscopy. The density (from 10^10 to 10^11 cm-2) and the size of QDs are carefully engineered while keeping a 1550 nm emission wavelength. To evaluate the potential of QDs for dual frequency oscillation, a critical parameter is the homogeneous linewidth. It is measured through Spectral Hole Burning (SHB) experiments using two tunable and continuous-wave lasers. In order to be as close as possible to the laser operation conditions, the SHB experiments are performed at high temperature levels and high carrier densities. In this talk, we will present our preliminary results from Spectral Hole Burning experiments conducted on both InAs/InP QDs and conventional InGaAs/InP QWs. The dedicated homemade measurement apparatus will be presented as well. This work is supported by the IDYLIC ANR project (ANR-15-CE24-0034-01)

Composition profiles in InP/InAsP quantum well structures under the effect of reactives gases during dry etching processes — Luminescence and SIMS

International audienceWe have investigated the effects of reactive gases used during the deep reactive ion etching process of InP-based photonic structures in an inductively-coupled plasma (ICP) reactor. Samples with a specific structure, including 9 InAsP/InP quantum wells (QW) with graded As/P composition, were designed. Different chlorine-based gas chemistries were tested. Characterization was performed using cathodo-Iuminescence (CL) and photo-luminescence (PL) at different temperatures, and secondary ion mass spectrometry (SIMS). The luminescence lines display a blue shift upon exposure to the reactive gases, and a strong spectral sharpening. We discuss the influence of Cl diffusion and thermal processes during etching on these modifications

Direct measurement of the spectral dependence of Lamb coupling constant in a dual frequency quantum well-based VECSEL

Spectral dependence of Lamb coupling constant C is experimentally investigated in an InGaAlAs Quantum Wells active medium. An Optically-Pumped Vertical-External-Cavity Surface-Emitting Laser is designed to sustain the oscillation of two orthogonally polarized modes sharing the same active region while separated in the rest of the cavity. This laser design enables to tune independently the two wavelengths and, at the same time, to apply differential losses in order to extract without any extrapolation the actual coupling constant. C is found to be almost constant and equal to 0.84 +/- 0.02 for frequency differences between the two eigenmodes ranging from 45 GHz up to 1.35 THz. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen