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18150
01/07/2018

Modelling anisotropic lateral oxidation from circular mesas

S.CALVEZ, G.LAFLEUR, A.ARNOULT, A.MONMAYRANT, H.CAMON, G.ALMUNEAU

PHOTO, TEAM

Revue Scientifique : Optical Materials Express, Vol.8, N°7, pp.1762-1773, Juillet 2018 , N° 18150

Lien : https://hal.archives-ouvertes.fr/hal-01809678

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Abstract

In this paper, an iterative method to model the anisotropic lateral oxidation of circular structures is proposed and validated by confrontation to experimental data. The described model enables the efficient calculation of the temporal bi-dimensional evolution of the oxidation front shape, starting from a circular mesa, and progressing inward as a result of an anisotropic process combining an isotropic diffusion with an anisotropic reaction. The result of the developed model shows that the oxide aperture smoothly deforms from a circle to become more diamond-like, mimicking the experimental situation encountered when fabricating vertical-cavity surface-emitting lasers (VCSELs) on (100) wafers or, more generally, when oxidizing circular mesas of aluminum-containing III-V semiconductor on similarly oriented substrates.

143824
18102
01/06/2018

Coupled-mode analysis of vertically-coupled AlGaAs/AlOx microdisk resonators

C.ARLOTTI, G.LAFLEUR, A.LARRUE, P.F.CALMON, A.ARNOULT, G.ALMUNEAU, O.GAUTHIER-LAFAYE, S.CALVEZ

PHOTO, TEAM

Revue Scientifique : IEEE Journal of Quantum Electronics, Vol.54, N°3, Juin 2018 , N° 18102

Lien : https://hal.laas.fr/hal-01741465

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This article reports the experimental and theoretical assessments of the optical characteristics of recently-introduced vertically-coupled microdisk resonators made by selective oxidation of AlGaAs multilayer structures. Experimental measurements show that the Q-factors are in the 10 3 to 10 4 range for diameters ranging from 75 to 300 µm. To establish the origins of this limited performance a coupled-mode-theory-based model of the single-access-waveguide-coupled resonator system was developed. It includes features which are specific to oxide-based vertically-coupled resonators, namely losses towards the slab waveguide lying under the resonator and a coupling region with an asymmetric and multilayer structure. Setting this simulation tool required the proposal and validation of a general criterion to select an appropriate set of decomposition permittivity profiles to be able to accurately model the characteristics of these more complex couplers using the coupled-mode-theory approach. This theoretical development is generic and can be now deployed to simulate any device which includes multi-waveguide couplers with arbitrary piece-wise-constant profile of the dielectric permittivity. Exploiting this particular development and experimental measurements of the disk sidewall roughness and of the coupling lengths, the calculated and experimental Q-factors are found to be in good agreement and allow establishing that the current performance is limited by the scattering losses and the slab-leakage losses for small-and large-diameter devices respectively.

143354
18115
07/05/2018

High-Performance Compact 3-D Solenoids for RF Applications

A.CAYRON, C.VIALLON, O.BUSHUEVA, A.GHANNAM, T.PARRA

MOST, 3DiS Technologies

Rapport LAAS N°18115, doi 10.1109/LMWC.2018.2831438, Mai 2018, 3p.

Lien : https://hal.archives-ouvertes.fr/hal-01778992

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A cost-effective technology is proposed for the integration of very compact and high-performance 3-D solenoid inductors. Based on a two metal level process, it involves a 3-D copper electroplating step for simultaneous integration of vertical and upper sections of coils. Several solenoids fabricated on a glass substrate and ranging from 2.3 nH to 9.5 nH are presented. The best performance is experimentally achieved by a 3-turn 3 nH inductor showing a maximum Q-factor of 58 at 5.6 GHz and a self-resonant frequency of 19 GHz. The best inductance density of 63 nH/mm 2 is reached by an 8-turn 9.5 nH solenoid.

143436
18127
22/04/2018

Design of an Electro-absorption modulator for integration onto a VCSEL

L.MARIGO-LOMBART, S.CALVEZ, A.ARNOULT, A.RUMEAU, C.VIALLON, H.THIENPONT, G.ALMUNEAU, K.PANAJOTOV

PHOTO, TEAM, I2C, MOST, Bruxelles

Manifestation avec acte : SPIE Photonics Europe. Semiconductor Lasers and Laser Dynamics VII ( SPIE photonics ) 2018 du 22 avril au 26 avril 2018, Strasbourg (France), Avril 2018, 2p. , N° 18127

Lien : https://hal.laas.fr/hal-01780281

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In this work, we have realized a complete optimization cycle from structure design, fabrication to devices characterization, and finally analysis b ased on our model of Asymmetric - Fabry - Perot vertica l electro - absorption modulator. In order to achieve enhanced dynamic absorption effect with a minimized number of MQW, we used a perturbative quantum - confined Stark - effect based on a simple absorption mode l and transfer matrix calculations and optimize the modulation figures of merit as a function of different design parameters under varying applied electrical fields. The epitaxial growth by MBE of different EAM and EAM - VCSEL structures has been done, supp orted by intermediate optical measurements enabling to identify the EAM cavity and VCSEL cavity respective positions. Finally, first static characterizations are done and demonstrate the expected modulation properties of the device. A very good agreement of theoretical predictions for both the effect of the applied field and the temperature on the excitonic peak position and the Fabry - Perot shift experimentally measured on different fabricated EAM structures has been achieved. Thanks to th is, we are now able to design an optim al VCSEL structure with integrated electro - absorption modulator . To aim for very high frequency efficient electrical injection we focused also on the BCB characterization up to 110 Ghz and the injection scheme de sign specific to this triple electrode device. These measurements are of high interest for the optimum design of the access while considering the parasitic effects. We then compare coplanar and micro strip lines access, with a taper or not, to decrease the pad capacitance and so increase the cut - off frequency.

143573
18027
02/03/2018

Comprehensive modeling of multimode fiber sensors for refractive index measurement and experimental validation

H.APRIYANTO, G.RAVET, O.BERNAL, M.CATTOEN, HC.SEAT, V.CHAVAGNAC, F.SURRE, J.H.SHARP

OSE, GET- UMR 5563, City University, Glasgow

Rapport LAAS N°18027, Mars 2018, 11p.

Non diffusable

142554
17479
02/03/2018

Soft mold NanoImprint Lithography: A versatile tool for sub-wavelength grating applications

S.PELLOQUIN, S.AUGÉ, K.SHARSHAVINA, J.B.DOUCET, A.HELIOT, H.CAMON, O.GAUTHIER-LAFAYE

PHOTO, TEAM

Revue Scientifique : Microsystem Technologies, 5p., Mars 2018 , N° 17479

Lien : https://hal.laas.fr/hal-01706924

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Due to its independency to the substrate used, Soft mold NanoImprint Lithography (S-NIL) is a technique of great interest in particular for the fabrication of optical devices. We demonstrate a mature pathway for the realization of optical filters from the conception to the optical characterization. Those filters can be realized on large surfaces (up to 6" diameter wafers) with high conformity on various substrates. Quality of the transfer will be discussed throughout the process and optical performances compared to those obtained with classical techniques. In this paper we fabricated tunable spectral filters with a grating periodicity down to 260 nm and imprint surfaces up to 6". Physical conformity of the gratings will be discussed in terms of long-range stitching obtained on 6" Si hard mold, dimensional shrinkage during thermal NanoImprint on Zeonor® soft mold and conformity towards patterned hard mold throughout the process.

142589
18100
01/03/2018

Vertical electro-absorption modulator design and its integration in a VCSEL

L.MARIGO-LOMBART, S.CALVEZ, A.ARNOULT, H.THIENPONT, G.ALMUNEAU, K.PANAJOTOV

PHOTO, TEAM, Bruxelles

Revue Scientifique : Journal of physics. D, Applied physics, Vol.51, N°14, 145101p., Mars 2018 , N° 18100

Lien : https://hal.laas.fr/hal-01780259

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Abstract

Electro-absorption modulators, either embedded in CMOS technology or integrated with a semiconductor laser, are of high interest for many applications such as optical communications, signal processing and 3D imaging. Recently, the integration of a surface-normal electro-absorption modulator into a vertical-cavity surface-emitting laser has been considered. In this paper we implement a simple quantum well electro-absorption model and design and optimize an asymmetric Fabry–Pérot semiconductor modulator while considering all physical properties within figures of merit. We also extend this model to account for the impact of temperature on the different parameters involved in the calculation of the absorption, such as refractive indices and exciton transition broadening. Two types of vertical modulator structures have been fabricated and experimentally characterized by reflectivity and photocurrent measurements demonstrating a very good agreement with our model. Finally, preliminary results of an electro-absorption modulator vertically integrated with a vertical-cavity surface-emitting laser device are presented, showing good modulation performances required for high speed communications.

143337
18110
01/03/2018

Effect of low and staggered gap quantum wells inserted in GaAs tunnel junctions

K.LOUARN, Y.CLAVEAU, L.MARIGO-LOMBART, C.FONTAINE, A.ARNOULT, F.PIQUEMAL, A.BOUNOUH, N.CAVASSILAS, G.ALMUNEAU

PHOTO, IM2NP, TEAM, LNE, CEA LIST

Revue Scientifique : Journal of physics. D, Applied physics, Vol.51, N°14, 145107p., Mars 2018 , N° 18110

Lien : https://hal.archives-ouvertes.fr/hal-01761772

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In this article, we investigate the impact of the insertion of either a type I InGaAs or a type II InGaAs/GaAsSb quantum well on the performances of MBE-grown GaAs tunnel junctions (TJs). The devices are designed and simulated using a quantum transport model based on the non-equilibrium Green's function formalism and a 6-band k.p Hamiltonian. We experimentally observe significant improvements of the peak tunneling current density on both heterostructures with a 460-fold increase for a moderately doped GaAs TJ when the InGaAs QW is inserted at the junction interface, and a 3-fold improvement on a highly doped GaAs TJ integrating a type II InGaAs/GaAsSb QW. Thus, the simple insertion of staggered band lineup heterostructures enables us to reach a tunneling current well above the kA cm−2 range, equivalent to the best achieved results for Si-doped GaAs TJs, implying very interesting potential for TJ-based components, such as multi-junction solar cells, vertical cavity surface emitting lasers and tunnel-field effect transistors.

143394
17586
01/03/2018

Technique for wireless reading of passive microfluidic sensors

D.HENRY, H.AUBERT, P.PONS, J.LORENZO, A.LAZARO, D.GIRBAU

MINC, Rovira, UPC

Revue Scientifique : Electronics Letters, Vol.54, N°3, pp.150-151, Mars 2018 , N° 17586

Lien : https://hal.laas.fr/hal-01710134

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The remote reading of high-resolution microfluidic and passive (i.e. batteryless and chipless) temperature sensors is focused. These sensors are remotely interrogated from a 24 GHz frequency-modulated continuous-wave radar performing a mechanical beam scanning for locating the sensors and measuring the variation of sensors electromagnetic echo level due to temperature fluctuation. From radar measurement data, an estimator is proposed here for determining the meniscus position of the fluid inside the sensors microchannel and for deriving the temperature at the sensors location. It is shown that the estimator presents a convenient linear dependence with the meniscus position at the sensor location. The smallest measurable variation of the meniscus position is of 40 μm.

142741
18016
08/02/2018

Optical feedback flowmetry: Impact of particle concentration on the signal processing method

R.ATASHKHOOEI, E.E.RAMIREZ MIQUET, R.DA COSTA MOREIRA, A.QUOTB, S.ROYO, J.PERCHOUX

UPC, MPQ, OSE

Revue Scientifique : IEEE Sensors Journal, Vol.18, N°4, pp.1457-1463, Février 2018 , N° 18016

Lien : https://hal.archives-ouvertes.fr/hal-01685176

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Optical feedback interferometry (OFI) based flowmetry enables simple, robust, self-aligned and low cost systems to measure the fluid flow velocity with reasonable accuracy. The particle concentration in the fluid causes significant changes in the signal of OFI sensors. While the spectral analysis of the particle induced Doppler shift remains as the most usual approach to determine the flow properties, different processing algorithms have been proposed in order to evaluate the average flow velocity within the measurement volume. In this paper, the validity of the commonly used methods with regards to particle concentrations and flow rates is verified.

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