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

Dispersion monitoring for high-speed WDM networks via two-photon absorption in a semiconductor microcavity

Due to the continued demand for bandwidth, network operators have to increase the data rates at which individual wavelengths operate at. As these data rates will exceed 100 Gbit/s in the next 5-10 years, it will be crucial to be able to monitor and compensate for the amount of chromatic dispersion encountered by individual wavelength channels. This paper will focus on the use of the novel nonlinear optical-to-electrical conversion process of two-photon absorption (TPA) for dispersion monitoring. By incorporating a specially designed semiconductor microcavity, the TPA response becomes wavelength dependent, thus allowing simultaneous channel selection and monitoring without the need for external wavelength filterin

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

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

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

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

Electroswitchable red-NIR luminescence of ionic clustomesogen containing nematic liquid crystalline devices.

International audienceWe describe in this work several polyionic hybrid mol. compds. combining, by electrostatic interactions, liq. cryst. ammonium cations and tailor made molybdenum hexanuclear dianionic cluster units. All hybrids show nematic liq. cryst. behavior below 100 °C, no matter the nature of the metallic cluster apical and inner ligands. They also retain the shiny deep red photoluminescence properties of their parent cluster in the nematic phase. This nematic phase remains however quite viscous for all compds. and mixing them with com. available nematic LCs seems mandatory to integrate them into electroswitchable devices. This particularity conducted us to insert the best candidate in terms of homogeneity and stability of the clustomesogen/com. LC mixt. into a LC cell and study the behavior toward the application of an elec. stimulus. We show that the application of 30 V AC voltage allows observing a reversible modulation of the photoluminescence signal by about 52%. This work presents the first deep red photoluminescent transition metal cluster contg. device directed towards optoelectronic applications

Réalisation d’un laser à faible courant de seuil, avec des boites quantiques InAs/InP organisées et couplées latéralement

Nous présentons ici la réalisation d’un laser à faible courant de seuil avec des boites quantiques (QDs) organisées et couplées InAs/InP sur subsstrat (311)B pour une émission à 1.55 m. En effet, pour des hautes densités de QDs, une organisation périodique apparaît dans le plan. Cette organisation renforce le couplage latéral inter-boites. Des expériences de magnéto-photoluminescence permettent de mettre en évidence ces effets de couplage. Ce couplage améliore l’injection des porteurs. Une émission laser avec des faibles courants de seuil est obtenue avec de telles boites

Long-wavelength Vertical-Cavity Surface-Emitting Laser using an electro-optic index modulator with 10-nm tuning range

International audienceWe demonstrate an original approach to achieving a tunable 1.55-µm vertical-cavity surface-emitting laser. The tunability is based on an electro-optic index modulator using nano-sized droplets of liquid crystal as a phase layer. Such an approach can produce a robust and a low-cost device. A 10-nm tuning range with less than 170V applied voltage has been demonstrated. The device is formed by a conventional InP-based active region with an epitaxial and a dielectric Bragg mirror. This optically pumped device exhibits an excellent side-mode suppression ratio of higher than 20-dB over the whole spectral range

Thermal conductivity of InAs quantum dot stacks using AlAs strain compensating layers on InP substrate

International audienceThe growth and thermal conductivity of InAs quantum dot (QD) stacks embedded in GaInAs matrix with AlAs compensating layers deposited on (1 1 3)B InP substrate are presented. The effect of the strain compensating AlAs layer is demonstrated through Atomic Force Microscopy (AFM) and X-ray diffraction structural analysis. The thermal conductivity (2.7 W/m K at 300 K) measured by the 3ω method reveals to be clearly reduced in comparison with a bulk InGaAs layer (5 W/m K). In addition, the thermal conductivity measurements of S doped InP substrates and the SiN insulating layer used in the 3ω method in the 20-200 °C range are also presented. An empirical law is proposed for the S doped InP substrate, which slightly differs from previously presented results