Excited state absorption in the Si nanocluster-Er material system

Loh, W.H.; Kenyon, Anthony J.

doi:10.1109/lpt.2005.861266

Cited by 10 publications

(10 citation statements)

References 17 publications

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“…However, when ESA is present, such an increase will not be seen, as excited Er ions can still continue to accept energy from the nanoclusters. 31 We note that our results in this work also show that the nanocluster PL does not increase abruptly when the erbium PL saturates, implying ESA, which will decrease the overall quantum efficiency of the erbium luminescence.…”

Section: ͑15͒supporting

confidence: 52%

Generalized rate-equation analysis of excitation exchange between silicon nanoclusters and erbium ions

et al. 2008

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We discuss the use of rate equations to analyze the sensitization of erbium luminescence by silicon nanoclusters. In applying the general form of second-order coupled rate-equations to the Si nanocluster-erbium system, we find that the photoluminescence dynamics cannot be described using a simple rate equation model. Both rise and fall times exhibit a stretched exponential behavior, which we propose arises from a combination of a strongly distance-dependent nanocluster-erbium interaction, along with the finite size distribution and indirect band gap of the silicon nanoclusters. Furthermore, the low fraction of erbium ions that can be excited nonresonantly is a result of the small number of ions coupled to nanoclusters.

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Section: ͑15͒supporting

confidence: 52%

Generalized rate-equation analysis of excitation exchange between silicon nanoclusters and erbium ions

et al. 2008

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“…6 Various methods have been used to enhance the optical performance of Er 3+ -doped SiO 2 waveguide regardless of the low solubility limit. Some of these methods include utilization of sensitizers such as silicon nanoclusters, [7][8][9][10][11] incorporation of Er in Si x N y , 12 co-implantation of silver in silica glass, 13 preparation of multilayers of Er-doped SiO 2 with silicon rich silicon dioxide ͑SRSO͒, [14][15][16] and synthesis of Er-doped oxide nanostructures. 17,18 Much research effort has also been directed in determining the absorption cross sections for these material systems.…”

Section: Introductionmentioning

confidence: 99%

Optical properties of Y2O3 thin films doped with spatially controlled Er3+ by atomic layer deposition

Hoang¹,

Van²,

Sawkar-Mathur³

et al. 2007

Journal of Applied Physics

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Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. We report in this work the optical properties of Er 3+ -doped Y 2 O 3 , deposited by radical enhanced atomic layer deposition. Specifically, the 1.53 m absorption cross section of Er 3+ in Y 2 O 3 was measured by cavity ring-down spectroscopy to be ͑1.9± 0.5͒ ϫ 10 −20 cm 2 , about two times that for Er 3+ in SiO 2 . This is consistent with the larger Er 3+ effective absorption cross section at 488 nm, determined based on the 1.53 m photoluminescence yield as a function of the pump power. X-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy were used to determine the film composition, which in turn was used to analyze the extended x-ray absorption fine structure data, showing that Er was locally coordinated to only O in the first shell and its second shell was a mixture of Y and Er. These results demonstrated that the optical properties of Er 3+ -doped Y 2 O 3 are enhanced, likely due to the fully oxygen coordinated, spatially controlled, and uniformly distributed Er 3+ dopants in the host. These findings are likely universal in rare-earth doped oxide materials, making it possible to design materials with improved optical properties for their use in optoelectronic devices.

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“…4 In a recent paper, we pointed out the existence of Er excited state absorption ͑ESA͒ occurring in this material system. 8 We propose here that ESA is the primary cause for the low fraction of Er ions excited by the Si-nc.…”

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confidence: 95%

“…Back-transfer and Auger processes from the Er to the Si-nc were neglected, as it has been experimentally shown that they are unlikely to occur for this material. 11 For simplicity, and in keeping with results from our previous analysis of ESA in this system, 8 the ESA coupling coefficient is taken to be comparable ͑equal͒ to the Si-nc-Er ground state coupling coefficient. We performed the calculations with ESA present, and without ESA for comparison.…”

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confidence: 99%

Er 3 + excited state absorption and the low fraction of nanocluster-excitable Er3+ in SiOx

Otón

Loh

Kenyon

2006

Applied Physics Letters

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Despite the observation by a number of groups of a strong luminescence sensitization effect of erbium ions by excitation exchange from silicon nanoclusters, there is considerable experimental evidence that the fraction of Er ions excited by Si-nc is actually very low for much of the material reported. In this work, we examine the evidence and point out that Er excited state absorption is the likely cause. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2227637͔In recent years, silicon nanocluster-sensitized Er-doped materials have generated great interest, as it has been demonstrated that silicon nanoclusters ͑Si-nc͒ can transfer their energy very effectively to the Er ions surrounding them. The attraction of this indirect excitation is twofold: ͑i͒ the excitation cross section of the Si-nc is at least four orders of magnitude greater than that of rare earths in silica and ͑ii͒ the broadband absorption spectrum of the Si-nc allows pumping with sources such as light-emitting diodes ͑LEDs͒. The latter would dramatically lower the cost of Er-doped amplifiers, and allow pumping geometries such as top-down nonguided pumping, which would enable easy integration of amplifiers in planar optical circuits. However, no lasing action has been achieved to date. Indeed, there is cumulating evidence that, for much of the material that has been reported, the fraction of Er ions that can be excited by Si-nc is actually very low-of the order of a few percent or less. Clearly, this issue will need to be understood and resolved in order for viable lasers and amplifiers to be realized from this material system.There is now documented evidence from multiple groups, although it may not always have been explicitly recognized, that the fraction of Er ions that are excitable by Si-ncs is often quite low. 1,2 For example, for the data presented by Fujii et al., 1 the Er photoluminescence ͑PL͒ for two samples with the same Er concentration, one of which contained Si-nc ͓silicon-rich oxide ͑SRO͔͒ and the other without ͑SiO 2 ͒, was reported to differ by a factor of 30 under the same pumping conditions ͑see Fig. 1͒. It is straightforward to show by rate equation analysis that the Er excited state populations are given bywhere is the Er pump absorption cross section, the Er luminescence lifetime, P the pump flux, N Er the Er ion concentration, k the Si-nc to Er excitation transfer coefficient, and n b is the Si-nc excited state population. At the maximum pump power reported ͑1.5 W / cm 2 ͒, the SRO sample is in the saturation regime while the SiO 2 sample is still in the linear regime; therefore the ratio of the number of excited Er ions in the two samples can be simply estimated asTaking 488 nm ϳ 10 −20 cm 2 , = 10 ms, and P =4 ϫ 10 18 cm 2 s −1 ͑corresponding to 1.5 W / cm 2 ͒, this yields an Er concentration ratio of 2000. As the experimentally observed PL ratio is only 30, this indicates that just 1.5% of the available Er ions in the SRO sample have been excited. This conclusion seems surprising considering that, for the volume frac...

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Excited state absorption in the Si nanocluster-Er material system

Cited by 10 publications

References 17 publications

Generalized rate-equation analysis of excitation exchange between silicon nanoclusters and erbium ions

Generalized rate-equation analysis of excitation exchange between silicon nanoclusters and erbium ions

Optical properties of Y2O3 thin films doped with spatially controlled Er3+ by atomic layer deposition

Er 3 + excited state absorption and the low fraction of nanocluster-excitable Er3+ in SiOx

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