Impact of the capping layers on lateral confinement in InAs/InP quantum dots for 1.55 um laser applications srudied by magneto-photoluminescence.

We have used magnetophotoluminescence to study the impact of different capping layer material combinations (InP, GaInAsP quaternary alloy, or both InP and quaternary alloy) on lateral confinement in InAs/InP quantum dots (QDs) grown on (311)B orientated substrates. Exciton effective masses, Bohr radii, and binding energies are measured for these samples. Conclusions regarding the strength of the lateral confinement in the different samples are supported by photoluminescence at high excitation power. Contrary to theoretical predictions, InAs QDs in quaternary alloy are found to have better confinement properties than InAs/InP QDs. This is attributed to a lack of lateral intermixing with the quaternary alloy, which is present when InP is used to (partially) cap the dots. The implications of the results for reducing the temperature sensitivity of QD lasers are discussed. ©2005 American Institute of Physic

Finely tunable 1.55 µm emitting VeCSELs for embedded and compact optical and microwave systems

International audienceCompact wavelength-tunable laser sources are important for the development of optical based system units which can be used for numerous applications, ranging from optical communications, optical sensors, and even microwave photonics and high resolution spectroscopy. In most cases, large mode-hop-free wavelength tuning is of high interests to increase system performances and versatilities. In the metrology area, a small but very accurate wavelength tuning is required to fulfill system requirements. Thanks to their long cavity, VeCSELs offer the opportunity to get small laser wavelength linewidth, and shot noise limited behavior (class-A lasers). In this work we summarize the objectives and the preliminary results of the ANR Astrid HYPOCAMP project (HYbrid Polarisation controlled and mOnolithic tunable vertical Cavity surface emitting lAsers, for eMbedded and comPact optical and microwave systems), which is lead by FOTON in partnership with IPR (Rennes), CNRS-LAAS (Toulouse), CNRS-LPN (Marcoussis) and Telecom Bretagne. The project aims to develop a compact, reliable and low cost monolithic and versatile technology for the realization of tunable V(e)CSEL lasers, emitting in the 1.55 µm range (InP-based technology). In Fig.1 the optically-pumped external-cavity version of the device is presented

Si wafer bonded of a-Si/a-SiNx distributed Bragg reflectors for 1.55-µm wavelength vertical cavity surface emitting lasers

International audienceAmorphous silicon (a-Si) and amorphous silicon nitride (a-SiNx) layers deposited by magnetron sputtering have been analyzed in order to determine their optical and surface properties. A large value of ~1.9 of index difference is found between these materials. Distributed Bragg reflectors (DBR) based on these dielectric materials quarter wave layers have been studied by optical measurements and confronted to theoretical calculations based on the transfer matrix method. A good agreement has been obtained between the experimental and expected reflectivity. A maximum reflectivity of 99.5% at 1.55 µm and a large spectral bandwidth of 800 nm are reached with only four and a half periods of a-Si/a-SiNx. No variation of the DBR reflectivity has been observed with the time nor when annealed above 240°C and stored during few months. This result allows to use this DBR in a metallic bonding process to realize a vertical cavity surface emitting laser (VCSEL) with two dielectric a-Si/a-SiNx DBR. This bonding method using AuIn2 as the bonding medium and Si substrate can be performed at a low temperature of 240°C without damaging the optical properties of the microcavity. The active region used for this VCSEL is based on lattice-matched InGaAs/InGaAsP quantum wells and a laser emission has been obtained at room-temperature on an optically pumped device

Liquid crystal micro-cells for tunable VCSELs

International audienceWe recently demonstrated the tunability of a VCSEL with an intra-cavity liquid crystal layer. This demonstration was made on a macroscopic-sized sample with optical pumping. For a further development of this solution, it is necessary to place the liquid crystal on microscopic VCSEL chips. We developed a microtechnology process which makes it possible to fabricate liquid crystal micro-cells in a collective process

Growth of quantum wires for long-wavelength VCSEL with a polarized laser emission

International audienceWe report continuous-wave operation at room temperature for a 1.55-µm VCSEL where the active region is made up of quantum-well. Now, self-organized quantum wires grown on InP substrate is used to obtain polarized laser emission

Design of InGaAs/InP 1.55μm vertical cavity surface emitting lasers

International audienceThe design of an electrically pumped InGaAs quantum well based vertical cavity surface emitting laser (VCSEL) on InP substrate is presented. Such optically pumped VCSELs have already been demonstrated. To design electrically pumped VCSEL, three simulations steps are needed: optical simulation gives access to the electric field repartition, to design the active zone and the Bragg mirrors. Thermal simulation is helpful to design metallic contacts while the energy band diagram is obtained by electrical simulation to design the buried tunnel junction useful for carrier injection. All these simulations are compared to experiment

Design and Fabrication of GaInAsP/InP VCSEL with two a-Si/a-SiNx Bragg reflectors

International audienceWe report on the design and fabrication of a 1.55-μm wavelength Vertical Cavity Surface Emitting Lasers (VCSELs) which consists of two dielectric Bragg mirrors and a InGaAsP-based active region. The dielectric materials are amorphous silicon and amorphous silicon nitride. Layers of such materials have been deposited by magnetron sputtering and analyzed in order to determine their optical properties. A large refractive index difference of 1.9 is found between these materials. Distributed Bragg Reflectors (DBRs) based on these dielectric materials quarter wave layers have been studied by optical measurements and confronted to theoretical calculations based on the transfer matrix method. A maximum reflectivity of 99.5% at 1.55-μm and a large spectral bandwidth of 800nm are reached with only four and a half periods of a-Si/a-SiNx. The VCSEL was fabricated by metallic bonding process. This method allows to bond an InP-based active region as the gain medium on a Si substrate thanks to the formation of a Au–In alloy. This process is performed at a low temperature of 240◦C without damaging the optical properties of the microcavity. This VCSEL has been characterized by an optical pumping experiment with a low and a high-density optical power and a laser emission has been obtained at room-temperature

Design and fabrication of a tunable InP-based VCSEL using a electro-optic index modulator

International audienceWe present the first vertical surface emitting laser (VCSEL) operating at 1.55-μm comprising a electro-optic modulator inside its cavity. This material consists of nematic liquid crystal dispersed in a polymer material (nano-PDLC). This first VCSEL exhibits a 10 nm tuning range and an excellent side-mode suppression ratio higher than 20 dB over the whole spectral range. The device is formed by a conventional InP-based active region with an epitaxial and a dielectric Bragg mirror. The nano-PDLC layer length, close to 6 μm, is in agreement with a tunable laser emission without mode-hopping. Another decisive advantage, compared to mechanical solutions, is the tuning response time which is close to a few 10 μs to scan the full spectral range, making this device appropriate for some access network functions. This first version is optically pumped and requires 170 volts to obtain a 10 nm tunability

Multijunction photovoltaics: integrating III–V semiconductor heterostructures on silicon

International audienceGallium arsenide phosphide nitride shows promise for developing highefficiency tandem solar cells on low-cost silicon substrate

VCSEL à fils quantiques présentant une émission laser de 1647 à 1542 nm

National audienceLes lasers à cavité verticale émettant par la surface (VCSEL) présentent de grands intérêts pour des applications variées (télécommunication, capteurs, ..), d'autant plus si ces derniers s'avèrent stables et accordables en longueur d'onde. Au-delà du procédé technologique utilisé, cette dernière propriété est aussi très limitée par l'extension du gain spectral de la zone active. Nous présentons ici la réalisation d'un VCSEL émettant à 1.55 μm, et présentant une émission laser sur une plage en longueur d'onde de 105 nm