Modeling of optical amplifier waveguide based on silicon nanostructures and rare earth ions doped silica matrix gain media by a finite-difference time-domain method: comparison of achievable gain with Er3+ or Nd3+ ions dopants

A comparative study of the gain achievement is performed in a waveguide optical amplifier whose active layer is constituted by a silica matrix containing silicon nanograins acting as sensitizer of either neodymium ions (Nd 3+) or erbium ions (Er 3+). Due to the large difference between population levels characteristic times (ms) and finite-difference time step (10 --17 s), the conventional auxiliary differential equation and finite-difference time-domain (ADE-FDTD) method is not appropriate to treat such systems. Consequently, a new two loops algorithm based on ADE-FDTD method is presented in order to model this waveguide optical amplifier. We investigate the steady states regime of both rare earth ions and silicon nanograins levels populations as well as the electromagnetic field for different pumping powers ranging from 1 to 10 4 mW.mm-2. Furthermore, the three dimensional distribution of achievable gain per unit length has been estimated in this pumping range. The Nd 3+ doped waveguide shows a higher gross gain per unit length at 1064 nm (up to 30 dB.cm-1) than the one with Er 3+ doped active layer at 1532 nm (up to 2 dB.cm-1). Considering the experimental background losses found on those waveguides we demonstrate that a significant positive net gain can only be achieved with the Nd 3+ doped waveguide. The developed algorithm is stable and applicable to optical gain materials with emitters having a wide range of characteristic lifetimes.Comment: Photonics West , Feb 2015, San Francisco, United States. S, SPIE Proceedings, 9357 (935709), 2015, Physics and Simulation of Optoelectronic Devices XXIII. arXiv admin note: text overlap with arXiv:1405.533

Theoretical investigation of the more suitable rare earth to achieve high gain in waveguide based on silica containing silicon nanograins doped with either Nd3+ or Er3+ ions

We present a comparative study of the gain achievement in a waveguide whose active layer is constituted by a silica matrix containing silicon nanograins acting as sensitizer of either neodymium ions (Nd3+) or erbium ions (Er3+). By means of an auxiliary differential equation and finite difference time domain (ADE-FDTD) approach that we developed, we investigate the steady states regime of both rare earths ions and silicon nanograins levels populations as well as the electromagnetic field for different pumping powers ranging from 1 to 104 mW/mm2. Moreover, the achievable gain has been estimated in this pumping range. The Nd3+ doped waveguide shows a higher gross gain per unit length at 1064 nm (up to 30 dB/cm) than the one with Er3+ doped active layer at 1532 nm (up to 2 dB/cm). Taking into account the experimental background losses we demonstrate that a significant positive net gain can only be achieved with the Nd3+ doped waveguide

Determination of refractive index, thickness, and the optical losses of thin films from prism-film coupling measurements

International audienceWe present a method of analysis of prism-film coupler spectroscopy based on the use of transfer matrix and genetic algorithm, which allows the simultaneous determination of refractive index, thickness, and optical losses of the measured layer

Synthèse, caractérisation et modélisation de matériaux en couches minces pour l’optique en vue d’applications

Les travaux réalisés ces dernières années m’ont amené à combiner ces trois aspects : synthèse de matériaux, caractérisations et modélisation. A propos de la synthèse de matériau, j’ai utilisé la synthèse par voie chimique pendant ma thèse (film mince de PZT) et mon postdoc (film mince polymère). A Caen, les méthodes de synthèse utilisées sont des méthodes physiques comme la pulvérisation cathodique magnétron. Mes activités directes sont actuellement plus centrées sur la caractérisation et la modélisation des matériaux optiques, réalisés au sein de l’équipe NIMPH ou étudiés par l’intermédiaire de collaborations. Dans la suite du manuscrit, je vais détailler les travaux post-doctoraux expérimentaux et théoriques réalisés en Suède, à Caen et en collaboration avec des laboratoires partenaires. Certains sujets ayant fait l’objet de publications détaillées seront brièvement abordés d’autres sujets ayant fait l’objet de moins de publications seront plus densément développés

Effect of the Nd content on the structural and photoluminescence properties of silicon-rich silicon dioxide thin films

In this article, the microstructure and photoluminescence (PL) properties of Nd-doped silicon-rich silicon oxide (SRSO) are reported as a function of the annealing temperature and the Nd concentration. The thin films, which were grown on Si substrates by reactive magnetron co-sputtering, contain the same Si excess as determined by Rutherford backscattering spectrometry. Fourier transform infrared (FTIR) spectra show that a phase separation occurs during the annealing because of the condensation of the Si excess resulting in the formation of silicon nanoparticles (Si-np) as detected by high-resolution transmission electron microscopy and X-ray diffraction (XRD) measurements. Under non-resonant excitation at 488 nm, our Nd-doped SRSO films simultaneously exhibited PL from Si-np and Nd3+ demonstrating the efficient energy transfer between Si-np and Nd3+ and the sensitizing effect of Si-np. Upon increasing the Nd concentration from 0.08 to 4.9 at.%, our samples revealed a progressive quenching of the Nd3+ PL which can be correlated with the concomitant increase of disorder within the host matrix as shown by FTIR experiments. Moreover, the presence of Nd-oxide nanocrystals in the highest Nd-doped sample was established by XRD. It is, therefore, suggested that the Nd clustering, as well as disorder, are responsible for the concentration quenching of the PL of Nd3+

Impact of the annealing temperature on the optical performances of Er-doped Si-rich silica systems Impact of the annealing temperature on the optical performances of Er-doped Si-rich Silica systems

International audienceSeries of Er-doped Si-rich silicon oxide (SRSO:Er) layers were grown by magnetron sputtering at different temperatures from ambient to 500°C and then annealed between 600°C and 1100°C. They were characterized by spectroscopic and time-resolved photoluminescence (PL) measurements. Significant PL was detected at 1533 nm from the as-grown samples at T≥300°C excited by a non-resonant wavelength (476 nm), hence indicating the formation of Si-based sensitizers during the growth process. The PL intensity and the decay lifetime of Er 3+ ions were both greatly increased with the annealing temperature. An optimum temperature of annealing is obtained at 800°C, which is expected to favor the formation of very dense and small sensitizers. The fraction of Er coupled to sensitizers was found nearly 6-7 times higher than that reported so far in the literature. 1. Introduction The effective excitation cross section of Er 3+ ions in SiO 2 is increased by 10 3-10 4 with the insertion of Si-based sensitizers in the matrix. It was shown that an indirect excitation of Er 3+ ions occurs through Si nanoclusters (Si-nc) [1,2]. Such an energy transfer allows one to benefit from the broadband high absorbance of Si-nc for optical excitation and from the improved transport of carriers injected by electrical excitation. This paves the way to the achievement of Er 3+ population inversion by either optical or electrical pumping for integrated photonics, such as planar amplifier, laser, etc. Recent studies reported that, in conventional SRSO:Er materials, only a small fraction (<2%) of Er 3+ ions are effectively benefiting from the Si-nc-mediated excitation [3]. Such a low value is far from ensuring an inversion population of Er 3+ , but requires, on the contrary, more efforts and studies to enhance significantly the proportion of coupled Er in SRSO:Er samples. These latter are usually submitted to annealing processes to form Si nanoclusters (Si-nc) as sensitizers, to remove non-radiative defects and to activate (optically) the Er 3+ ions. Such a treatment may change, however, the structure of either the Si-based sensitizers or the Er 3+ ions. This work aims at investigating the influence of growth and annealing temperature on the optical properties of the SRSO:Er layers and to correlate it to the proportion of Er coupled to sensitizers

New Si-based multilayers for solar cell applications

In this article, we have fabricated and studied a new multilayer structure Si-SiO2/SiNx by reactive magnetron sputtering. The comparison between SiO2 and SiNx host matrices in the optical properties of the multilayers is detailed. Structural analysis was made on the multilayer structures using Fourier transform infrared spectroscopy. The effect of specific annealing treatments on the optical properties is studied and we report a higher visible luminescence with a control over the thermal budget when SiO2 is replaced by the SiNx matrix. The latter seems to be a potential candidate to replace the most sought SiO2 host matrix

SiNx:Tb3+--Yb3+, an efficient down-conversion layer compatible with a silicon solar cell process

SiN x : Tb 3+-Yb 3+, an efficient down-conversion layer compatible with silicon solar cell process Abstract Tb 3+-Yb 3+ co-doped SiN x down-conversion layers compatible with silicon Photovoltaic Technology were prepared by reactive magnetron co-sputtering. Efficient sensitization of Tb 3+ ions through a SiN x host matrix and cooperative energy transfer between Tb 3+ and Yb 3+ ions were evidenced as driving mechanisms of the down-conversion process. In this paper, the film composition and microstructure are investigated alongside their optical properties, with the aim of maximizing the rare earth ions incorporation and emission efficiency. An optimized layer achieving the highest Yb 3+ emission intensity was obtained by reactive magnetron co-sputtering in a nitride rich atmosphere for 1.2 W/cm${}^2$ and 0.15 W/cm${}^2$ power density applied on the Tb and Yb targets, respectively. It was determined that depositing at 200 {\textdegree}C and annealing at 850 {\textdegree}C leads to comparable Yb 3+ emission intensity than depositing at 500 {\textdegree}C and annealing at 600 {\textdegree}C, which is promising for applications toward silicon solar cells.Comment: Solar Energy Materials and Solar Cells, Elsevier, 201