Alexandre Arnoult

Precise Frequency Spacing in Photonic Crystal DFB Laser Arrays

We have developed integrated distributed-feedback laser arrays using photonic crystal waveguide on a membrane. They exhibit stable single-mode emission. Using both different lattice constants and a method called affine deformation of the crystal, we obtained extended control over the lasing wavelength. Laser arrays with laser-to-laser wavelength shifts as small as 0.3 nm are achieved.

Vertically Coupled Microdisk Resonators Using AlGaAs/AlOx Technology

In this letter, we report the first experimental demonstration of microdisk resonators that are vertically coupled to their buried access waveguides on III-V semiconductor epitaxial structures using an original fabrication process. The here-proposed and validated three-dimensional integration scheme exploits selective lateral thermal oxidation of aluminium-rich AlGaAs layers. Compared with the previously reported processing techniques, this new scheme is simpler as it does not require any planarization or substrate transfer steps. As a proof-of-principle demonstration of this approach, 250-μm diameter microdisk devices exhibiting quality factor reaching ~8500 have been successfully fabricated.

Structural and magnetic properties of He+ irradiated Co2MnSi Heusler alloys

We have investigated the atomic disorder induced by a 150 keV He+ ion irradiation in a 40 nmthick Co2MnSi Heusler alloy. Disorder parameters on each atomic site are deduced from normal and anomalous X-ray diffraction measurements with Co and CuKasources. While the film grows mainly in the L21 phase with inclusion of B2 grains, we observe an increase of both theMn-Si and Co-Mn exchanges with the ion fluence. HAADF-STEM analysis demonstrates that the increase inMn-Si disorder corresponds to a growing size of the B2 grains while the Co-Mnexchange is accounted for a D03 disorder type in the L21 matrix. These structural modifications are shown to decrease the average magnetization of the alloy, which is due to D03 disorder and local defects induced by irradiation.

TEM EDS analysis of epitaxially-grown self-assembled indium islands

Air Force Office of Scientific Research (AFOSR) [FA9550-13-1-0003, 12RY05COR]; National Science Foundation Atomic, Molecular and Optical Physics [NSF-AMOP 1205031]; Engineering Research Center for Integrated Access Networks (NSF ERC-CIAN) [EEC-0812072]; Arizona Technology and Research Initiative Funding (TRIF); Department of Defense through the National Defense Science and Engineering Graduate (NDSEG) Fellowship Program; Department of Energy (DOE) through the Office of Science Graduate Fellowship (SCGF), [DE-AC05-06OR23100]; French technology network RENATECH

Integration of Electro-Absorption Modulator in a Vertical-Cavity Surface-Emitting Laser

VCSELs became dominant laser sources in many short optical link applications such as datacenter, active cables, etc. Actual standards and commercialized VCSEL are providing 25 Gb/s data rates, but new solutions are expected to settle the next device generation enabling 100 Gb/s. Directly modulated VCSEL have been extensively studied and improved to reach bandwidths in the range of 26-32 GHz [Chalmers, TU Berlin], however at the price of increased applied current and thus reduced device lifetime. Furthermore, the relaxation oscillation limit still subsists with this solution. Thus, splitting the emission and the modulation functions as done with DFB lasers is a very promising alternative [TI-Tech, TU Berlin]. Here, we study the vertical integration of an ElectroAbsorption Modulator (EAM) within a VCSEL, where the output light of the VCSEL is modulated through the EAM section. In our original design, we finely optimized the EAM design to maximize the modulation depth by implementing perturbative Quantum Confined Stark Effect (QCSE) calculations, while designing the vertical integration of the EAM without penalty on the VCSEL static performances. We will present the different fabricated vertical structures, as well as the experimental electrical and optical static measurements for those configurations demonstrating a very good agreement with the reflectivity and absorption simulations obtained for both the VCSEL and the EAM-VCSEL structures. Finally, to reach very high frequency modulation we studied the BCB electrical properties up to 110 GHz and investigated coplanar and microstrip lines access to decrease both the parasitic capacitance and the influence of the substrate.

Coupled-Mode Analysis of Vertically Coupled AlGaAs/AlOx Microdisk Resonators

This paper reports the experimental and theoretical assessments of the optical characteristics of recently introduced vertically coupled microdisk resonators made by the selective oxidation of AlGaAs multilayer structures. Experimental measurements show that the Q-factors are in the 103–104 range for diameters ranging from 75 to

Photonic crystal single-mode DFB laser array with precise frequency spacing

300~mu text{m}

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

. 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 toward 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 multiwaveguide 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.

Contrôle des fronts d'oxydation d'AlGaAs pour l'optique guidée

We have developed integrated DFB laser arrays using photonic crystal waveguide on membrane. They exhibit stable and controlled single-mode emissions with wavelength spacings as small as 0.3 nm.