A. Carenco

Ingaasp/ingaasp multiple-quantum-well modulator with improved saturation intensity and bandwidth over 20 ghz

A single-mode modulator was realized from an AP-MOCVD grown structure. The multiple-quantum-well electroabsorptive material is made of shallow InGaAsP wells separated by InGaAsP barriers. It exhibits at 1.54 mu m (TE) a 17 dB extinction ratio for a 3 V drive voltage, a 2.7 dB on-state loss and a small-signal bandwidth over 20 GHz with 1-2 mW of coupled optical power. >

Monolithic integration of an InP based polarization diversity heterodyne photoreceiver with electrooptic adjustability

In this paper we describe the monolithic integration, in the InP/InGaAsP material system, of a polarization diversity optical heterodyne receiver. The study concerns different components which are part of the device: polarization splitters, adjustable 3 dB TE and TM directional couplers, waveguide integration with PIN photodiodes, modal tapers, and JFETs. All these devices are developed in a compatible integration approach, as building blocks of the overall device. Eventfully, two circuit demonstrators-a polarization-diversity optical circuit integrated with two balanced-PIN pairs and a coupler integrated with a balanced-PIN pair and JFET amplifier-are presented. These two circuits show very good characteristics in terms of internal loss, rejection ratio, electrical bandwidth, and input noise, similar to hybrid circuits. This work paves the way for the use of complex integrated photoreceivers for system application. >

Wannier-Stark localization in a 1.55 mu m InGaAs/InAlAs superlattice waveguide modulator structure

The authors present an optical waveguide modulator structure based on Wannier-Stark localization in a InGaAs-InAlAs superlattice. Optical waveguide transmission below the superlattice bandgap displays expected F/sup -1/ oscillatory behavior leading to various modulation schemes. An 11 dB extinction ratio was obtained by applying a 0.7 V drive voltage to a 100 mu m long waveguide device operating at 1.55 mu m under a transverse-electric (TE)-polarization mode. On-state attenuation was 5 dB. Lower open-state attenuation (3 dB) can be obtained simultaneously with a higher extinction ratio (13 dB) but in that case a larger drive voltage (1.6 V) is needed.<<ETX>>

Quasi planar spot-size transformer for efficient coupling between a cleaved fibre and an InP/InGaAsP rib waveguide

A spot-size transformer structure is proposed for InP/InGaAsP double-heterostructure (DH) rib waveguide. Vertical expansion of a factor of 7 is achieved with 3 dB internal loss. Coupling from standard cleaved fibre (11 /spl mu/m diameter mode) to a DH rib waveguide (5.8/spl times/0.8 /spl mu/m large mode), is achieved with 4.5 dB polarisation independent loss. Coupling tolerances are highly relaxed. The fabrication method uses a thin cladding layer which ends up to a quasi-planar structure suitable with further integration process.<<ETX>>

InP-based 10-GHz bandwidth polarization diversity heterodyne photoreceiver with electrooptical adjustability

A polarization diversity optical receiver, integrated with two pairs of balanced photodiodes in the InP/InGaAsP material system, is described. This circuit includes two polarization splitters based on modal birefringence and, for the first time, adjustable 3-dB TE and TM directional couplers (relaxing fabrication tolerances). On-chip losses are below 2.5 dB (TE) and 5.5 dB (TM). Waveguide to PIN coupling efficiency is >95%. Polarization crosstalk is in the 9-10-dB range, 3-dB couplers balance can be recovered, and common mode rejection ratio (CMRR) lower than -30 dB is obtained and remains below -20 dB over 6 GHz. Balanced receiver circuit 3-dB bandwidth is in excess of 10 GHz.<<ETX>>

Polarization-independent filtering in a grating-assisted horizontal directional coupler

We report here on the design and the first realization of a grating-assisted horizontal directional coupler filter exhibiting a highly reduced polarization sensitivity. The filter, which is based on InP-InGaAsP materials, is particularly suitable for integration in a 1.3/spl plusmn/1.3 /spl mu/m duplexer. A polarization dependence below 1 dB has been measured for the separation of two 10 nm wide channels, respectively centered at 1.28 /spl mu/m and 1.32 /spl mu/m, for a rejection ratio of 10 dB.<<ETX>>

Efficient optical waveguide modulation based on Wannier-Stark localization in a InGaAs-InAlAs superlattice

We report the observation of Wannier-Stark localization in a InGaAs-InAlAs superlattice waveguide. Using the oblique transition connecting electrons and holes localized in adjacent wells we achieve efficient intensity modulation at 1 . 57jim incident light wavelength under TE polarization mode. A 16 dB extinction ratio is obtained by applying a 0. 75V drive voltage to a 320 j. tm long waveguide. On-state attenuation is only 3 dB.

Waveguide-fed PIN-HFET receiver at 2.5 Gbit/s integrated on InP

We report the monolithic integration of a building block, a waveguide-fed photoreceiver, comprising a semiconductor waveguide, a PIN photodiode, and a 3 stage low noise preamplifier, based on 0.5 /spl mu/m gate length high performance HFETs. Internal sensitivities better than -27dBm at 2.5Gbit/s and -25dBm at 5Gbit/s have been measured.

Influence des effets de contrainte induits par la température sur la conversion TE-TM dans des guides planaires de YIG substitué

RésuméLa possibilité d’accorder la biréfringence linéaire d’un guide magnétooptique en couche mince en jouant sur la température du guide a été démontrée. A l’aide de cette méthode, l’accord de phase entre les modes te0 et tm0 couplés par effet Faraday, une condition nécessaire à la réalisation d’un isolateur intégré magnétooptique basé sur la conversion de modes, a ete obtenu dans une double couche de grenat d’yttrium et de fer substitué par des atomes de gadolinium et de gallium. L’égalisation de phase a été obtenue pour une température du guide de 85°C. Cette température peut êetre ajustée en modifiant légèerement les substitutions en gadolinium et en gallium comme le prouve l’accord de phase observé dans un guide à température ambiante.AbstractWe have demonstrated the tuning of linear birefringence in magnetooptic planar thin film waveguides by temperature adjustment. Using this method, phase-matching between coupled te0and tm0 modes, a necessary condition for the integrated optical isolator based on mode conversion, has been obtained at λ = 1.52 µm in bilayer gadolinium gallium substituted yig films. The waveguide temperature was 85°C. Moreover, phase-matching temperature can be modified by a slight variation of gadolinium and gallium substitutions as shown by a phase-matching observed in a waveguide at room temperature.

Conversion paramétrique de fréquence infrarouge visible, étude prospective

RésuméAprès un rappel du principe de la conversion paramétrique de fréquence dans les matériaux non linéaires, on en étudie les deux principales formes d’application à la détection infrarouge. On passe d’abord en revue les études concernant la détection ponctuelle d’un faisceau monochromatique support d’informations. On évalue ensuite les perspectives offertes par cinq matériaux non linéaires prometteurs: GaSe, ZnGeP2, AgGaS2, Ag3AsS3 et α-HgS,dans le domaine de l’imagerie infrarouge. Les caractéristiques potentielles des convertisseurs sont comparées à celles des autres principaux détecteurs et imageurs infrarouges.