Si nanoclusters coupled to Er3+ ions in a SiO2 matrix for optical amplifiers (original) (raw)
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Optically active Er3+ ions in SiO2 codoped with Si nanoclusters
Journal of Applied Physics, 2009
Optical properties of directly excited erbium ͑Er 3+ ͒ ions have been studied in silicon rich silicon oxide materials codoped with Er 3+. The spectral dependence of the direct excitation cross section ͑ dir ͒ of the Er 3+ atomic 4 I 15/2 → 4 I 11/2 transition ͑around 0.98 m͒ has been measured by time resolved-photoluminescence measurements. We have determined that dir is 9.0Ϯ 1.5 ϫ 10 −21 cm 2 at 983 nm, at least twice larger than the value determined on a stoichiometric SiO 2 matrix. This result, in combination with a measurement of the population of excited Er 3+ as a function of the pumping flux, has allowed quantifying accurately the amount of optically active Er 3+. This concentration is, in the best of the cases, 26% of the total Er population measured by secondary ion mass spectrometry, which means that only this percentage could provide optical gain in an eventual optical amplifier based on this material.
Er-Coupled Si Nanocluster Waveguide
IEEE Journal of Selected Topics in Quantum Electronics, 2006
Rib-loaded waveguides containing Er 3+ -coupled Si nanoclusters (Si-nc) have been produced to observe optical gain at 1535 nm. The presence of Si-nc strongly improves the efficiency of Er 3+ excitation but may introduce optical loss mechanisms, such as Mie scattering and confined carrier absorption. Losses strongly affect the possibility of obtaining positive optical gain. Si-nc-related losses have been minimized to 1 dB/cm by lowering the annealing time of the Er 3+ -doped silicon-rich oxide deposited by reactive magnetron cosputtering. Photoluminescence (PL) and lifetime measurements show that all Er 3+ ions are optically active while those that can be excited at high pump rates via Si-nc are only a small percentage. Er 3+ absorption cross section is found comparable to that of Er 3+ in SiO 2 . However, dependence on the effective refractive index has been found. In pump-probe measurements, it is shown how the detrimental role of confined carrier absorption can be attenuated by reducing the annealing time. A maximum signal enhancement of about 1.34 at 1535 nm was measured.
Maximum fraction of Er3+ ions optically pumped through Si nanoclusters
Journal of Luminescence, 2006
By quantifying the amount of excited Er ions and considering the interaction distance between Si nanoclusters (Si-ncs) and the nearby Er ions, we were able to determine the maximum excitable Er concentration, when indirectly pumped through the Si-ncs. Our study was carried out on silica layers codoped with Si clusters and Er ions, grown by reactive magnetron sputtering. Si-rich silica layers were formed with different amounts of Si excess and doped to a wide range of Er concentrations. Thermal treatments were performed at 900 1C for different durations to maximize the Er emission at 1540 nm. The saturation limit of Er ions optically excitable through the Si-ncs was found about 3% of the total concentration. Simulations were carried out in order to explain this low value. The modelization takes into account the spatial distribution of the Er population, the measured size and density of Si clusters and the short-range character of the interaction between Er and Si-ncs. The small excitable fraction thus obtained appears as the ultimate intrinsic limitation to attain very high optical efficiency in such structures. r
Silicon Photonics and Photonic Integrated Circuits, 2008
The use of broadband efficient sensitizers for Er 3+ ions relaxes the expensive conditions needed for the pump source and raises the performances of the optical amplifier. Within this context Si nanoclusters (Si-nc) in silica matrices have revealed as optimum sensitizers and open the route towards electrically pumped optical amplifiers. Up to date two have been the main limiting issues for achieving absolute optical gain, the first one is the low quantity of erbium efficiently coupled to the Si-nc while the second is the carrier absorption mechanism (CA) within the Si-nc, which generates additional losses instead of providing amplification.
On optical activity of Er[sup 3+] ions in Si-rich SiO[sub 2] waveguides
Applied Physics Letters, 2006
Photoluminescence spectroscopy was used to explore the optical activity of Er 3+ ions in Si-rich SiO 2 waveguides prepared by ion implantation. Measurements were performed for a series of materials characterized by different Si excess levels, Er concentrations, and annealing temperatures. The highest fraction of optically active Er 3+ ions which can be efficiently activated by nonresonant pumping was found to be 2.6%. This was realized in a waveguide with an Er concentration of ͓Er͔ =10 18 cm −3 and Si excess of 20%, annealed at 900°C. This optical activity level is insufficient to realize optical gain. It is therefore clear that further material improvement is needed before optical amplification in SiO 2 : Er matrices sensitized by Si nanocrystals/nanoclusters can be achieved.
Excitable Er fraction and quenching phenomena in Er-doped SiO2 layers containing Si nanoclusters
Physical Review B, 2007
This paper investigates the interaction between Si nanoclusters ͑Si-nc͒ and Er in SiO 2 , reports on the optical characterization and modeling of this system, and attempts to clarify its effectiveness as a gain material for optical waveguide amplifiers at 1.54 m. Silicon-rich silicon oxide layers with an Er content of 4 -6 ϫ 10 20 at./ cm 3 were deposited by reactive magnetron sputtering. The films with Si excess of 6 -7 at. %, and postannealed at 900°C showed the best Er 3+ photoluminescence ͑PL͒ intensity and lifetime, and were used for the study. The annealing duration was varied up to 60 min to engineer the size and density of Si-nc and optimize Si-nc and Er coupling. PL investigations under resonant ͑488 nm͒ and nonresonant ͑476 nm͒ pumping show that an Er effective excitation cross section is similar to that of Si-nc ͑ϳ10 −17 -10 −16 cm 2 ͒ at low pumping flux ͑ϳ10 16 -10 17 cm −2 s −1 ͒, while it drops at high flux ͑Ͼ10 18 cm −2 s −1 ͒. We found a maximum fraction of excited Er of about 2% of the total Er content. This is far from the 50% needed for optical transparency and achievement of population inversion and gain. Detrimental phenomena that cause depletion of Er inversion, such as cooperative up conversion, excited-stated absorption, and Auger deexcitations are modeled, and their impact in lowering the amount of excitable Er is found to be relatively small. Instead, Auger-type short-range energy transfer from Si-nc to Er is found, with a characteristic interaction length of 0.4 nm. Based on such results, numerical and analytical ͑Er as a quasi-two-level system͒ coupled rate equations have been developed to determine the optimum conditions for Er inversion. The modeling predicts that interaction is quenched for high photon flux and that only a small fraction of Er ͑0.2-2 %͒ is excitable through Si-nc. Hence, the low density of sensitizers ͑Si-nc͒ and the short range of the interaction are the explanation of the low fraction of Er coupled. Efficient ways to improve Er-doped Si-nc thin films for the realization of practical optical amplifiers are also discussed.
Towards an enhanced coupling between the Er ions and Si nanoclusters
Physica E: Low-dimensional Systems and Nanostructures, 2009
The reactive magnetron co-sputtering of two confocal SiO 2 and Er 2 O 3 cathodes in argon-hydrogen plasma was used to deposit Er-doped Si-rich-SiO 2 layers. The effects of deposition conditions (such as hydrogen rate and substrate temperature) and annealing treatment (temperature and time) on the structural, compositional and photoluminescence (PL) properties of the layers were examined. An enhancement was observed of both Er 3+ PL emission and Er 3+ lifetime at 1.54 mm in comparison with their counterparts for the best samples reported so far. It was shown that a lifetime as high as 9 ms can be reached, with comparable PL intensities for resonant and non-resonant excitation lines. The effective cross-section and the fraction of Er ions coupled to Si clusters are analyzed.
Applied Physics Letters, 2006
Absorption coefficient ͑␣ abs ͒ of Er 3+ ions coupled to Si nanoclusters ͑Si-nc͒ in SiO 2 has been determined by optical transmission measurements in rib-loaded waveguides characterized by different refractive indices, thus gauging an Er 3+ absorption cross section ͑ abs ͒ of 0.4-1.2 ϫ 10 −20 cm 2 at 1534 nm. Although no significant enhancement due to the presence of Si-nc was observed, a clear dependence on the refractive index has been found. Measurements of the decay lifetime permit one to model the behavior as due to both local and mean field variations caused by the composite nature of the core waveguide layer.
Optically active Er[sup 3+] ions in SiO[sub 2] codoped with Si nanoclusters
Journal of Applied Physics, 2009
Excitonic luminescence in two-dimensionally confined layered sulfide oxides Appl. Phys. Lett. 101, 191901 (2012) Effect of Li+ ions on enhancement of near-infrared upconversion emission in Y2O3:Tm3+/Yb3+ nanocrystals J. Appl. Phys. 112, 094701 (2012) Time-resolved photoluminescence spectroscopy of excitons in layered semiconductor PbI2 nanoclusters J. Appl. Phys. 112, 093708 Photoluminescence under high-electric field of PbS quantum dots AIP Advances 2, 042132 Additional information on J. Appl. Phys.
Journal of Luminescence, 2009
Reactive magnetron co-sputtering of two confocal SiO 2 and Er 2 O 3 cathodes in argon-hydrogen plasma was used to deposit Er-doped Si-rich SiO 2 layers. The effects of the deposition conditions (such as RF power applied on each cathode and total plasma pressure) and annealing treatment (temperature and duration) on structural, compositional and photoluminescence (PL) properties of the layers were examined. It was found that a significant enhancement of both Er 3+ PL intensity and emission lifetime up to 9 ms have been reached through monitoring of the conditions of both deposition process and annealing treatment. The effective absorption cross section and the fraction of Er ions coupled to Si clusters were analyzed. It was shown an increase of the fraction of Er 3+ ions coupled to Si up to 11%.