Ultrafast holography using charge-transfer polymers

Maniloff, Eric S.; Vacar, D.; McBranch, D.; Wang, Hsing‐Lin; Mattes, Benjamin R.; Gao, Jun; Heeger, Alan J.

doi:10.1016/s0030-4018(97)00241-1

Cited by 28 publications

(20 citation statements)

References 15 publications

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“…[18] The maximum diffraction efficiency is 1 % (~3 lm film thickness), which is comparable to our previously reported results for close-packed, self-assembled NQD films, [18] as well as to the highest diffraction efficiencies measured for thin films of conjugated polymers. [19] However, our new nanocomposites have significantly improved photostability and show consistent performance for several hours of illumination under ambient conditions and at room temperature. The fabricated nanocomposites also show strong optical gain performance.…”

mentioning

confidence: 88%

High‐Performance, Quantum Dot Nanocomposites for Nonlinear Optical and Optical Gain Applications

Petruska

Malko

Voyles³

et al. 2003

Advanced Materials

126

120

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Colloidal syntheses allow the fabrication of nearly monodisperse, semiconductor, nanocrystal quantum dots (NQDs) with sub-10 nm sizes.[1±4] Size-controlled spectral tunability, resulting from quantum confinement, and the ease of manipulating NQDs into complex assemblies make colloidal dots ideally suited to be building blocks for the bottom±up assembly of device structures. A significant challenge for optical applications of NQDs is the incorporation of nanoparticles into transparent host matrices while preserving NQD size monodispersity and high photoluminescence (PL) quantum yields (QYs). Additional challenges are associated with achieving high NQD filling factors, which are essential for enhancing optical nonlinearities and obtaining large gain magnitudes. Recently, Sundar, Eisler, and Bawendi described the fabrication of NQD±ti-tania composites with semiconductor volume fractions (f) of up to 12 %, [5] which were sufficient to realize the regimes of both amplified spontaneous emission (ASE) [5] and lasing. [6] In this report, we develop a generalized approach for the preparation of comparable materials designed in such a way as to improve the volume loading (up to 20 %) and to preserve the size monodispersity (< 7 %) and the high PL QYs (> 10 % at room temperature) of the NQDs in the matrices. Our studies of the nonlinear optical and light-amplification performances of these new materials indicate large magnitudes for both third-order nonlinear susceptibilities and optical gain. Furthermore, we demonstrate micro-ring lasing and efficient dynamic holographic gratings using these nanocomposites. Early approaches to solid-state NQD sol±gel nanocomposites were based on the direct growth of semiconductor particles in glass matrices.[7±10] This strategy resulted in large polydispersities, poorly controlled surface properties, and low filling factors. Subsequent trials focused on decoupling the NQD synthesis and sol±gel fabrication. [5,11,12] However, despite improvements in the NQD PL QYs, ASE and lasing were only recently realized in such matrix materials using surface-exchanged CdSe and CdSe(ZnS) core±shell NQDs prepared using trioctylphosphine oxide and trioctylphosphine as the surfactants. [5,6] We have recently modified this procedure to improve the loading of NQDs in the titania matrix as well as to demonstrate the applicability of this method to NQDs passivated with ligands other than phosphines. As an example, it has been shown that amines promote high PL efficiencies and produce QYs as large as 85 % in growth solutions without the need for inorganic overcoating.[4] The use of dots without an inorganic shell (ªbareº dots) can, in principle, allow higher filling factors than the use of core±shell NQDs. For example, if one attempts to compact ªbareº NQDs of a 2.5 nm radius (R) and core±shell dots of the same core size with only a twomonolayer-thick ZnS shell into the same volume, the volume fraction of CdSe is higher for ªbareº NQDs by a factor of 1.6. In this paper, we concentrate on nanocomposites based on ...

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mentioning

confidence: 88%

High‐Performance, Quantum Dot Nanocomposites for Nonlinear Optical and Optical Gain Applications

Petruska

Malko

Voyles³

et al. 2003

Advanced Materials

126

120

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“…In the case of ''photodoping,'' the redistribution of oscillator strength associated with subgap infrared absorption and the corresponding bleaching of the interband ( -*) transition provide a route to nonlinear optical (NLO) response. Real occupation of lowenergy excited states (Heeger et al, 1988;Maniloff et al, 1997) and virtual occupation of higher-energy excited states (in the context of perturbation theory; Chiang et al, 1992) lead to, respectively, resonant and nonresonant NLO response.…”

Section: E Charge Injection At a Metal-semiconducting Polymer (Ms) Imentioning

confidence: 99%

Nobel Lecture: Semiconducting and metallic polymers: The fourth generation of polymeric materials

2001

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“…21 This resonant nonlinearity can be measured directly by pulsed laser experiments such as four-wave mixing, as demonstrated in recent ultrafast holography experiments using blends of MEH-PPV and C 60 . 5 The results show that the early-time diffraction efficiency in the near-IR is dominated by a combination of phase ͑from ⌬n͒ and amplitude ͑from ⌬ ͒ gratings which arise from the complex inc (3) , which, in turn, originates from the excited-state absorption. For such pulsed experiments where the pulsewidth is much shorter than the lifetime of the excited species, the change in the optical constants scales linearly with pulse energy, and ⌬n can be expressed as follows: 20…”

Section: Nonlinear Responsementioning

confidence: 92%

“…Because of the nearly instantaneous response of the system to illumination and because of the tunability of the decay dynamics by fullerene concentration, 5 conjugated polymer/ fullerene blends are promising candidates for nonlinear optical ͑NLO͒ applications. Because the NLO response arises from excitation from the metastable charge-transferred excited state, total fluence within the decay time for back charge transfer is the relevant parameter.…”

Section: Introductionmentioning

confidence: 99%

“…Because the NLO response arises from excitation from the metastable charge-transferred excited state, total fluence within the decay time for back charge transfer is the relevant parameter. Pulsed laser experiments have already shown 5 that these blends can be used for ultrafast holography with good diffraction efficiency, indicative of an incoherent third-order NLO susceptibility of the order 10 Ϫ8 esu. Larger values are anticipated from longer pump pulses and from probing at wavelengths where ⌬n is largest.…”

Section: Introductionmentioning

confidence: 99%

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Photo-induced changes in the complex index of refraction in conjugated polymer/fullerene blends

Miller

Lee

Hasharoni

et al. 1998

The Journal of Chemical Physics

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Photo-induced changes in the complex index of refraction in conjugated polymer/fullerene blends Miller, E. K.; Lee, K.; Hasharoni, K.; Hummelen, J. C.; Wudl, F.; Heeger, A. J. Take-down policy If 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.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. We report steady-state photo-induced absorption ͑PIA͒ and photo-induced reflectance ͑PIR͒ in films of poly͓2-methoxy-5-͑2Ј-ethyl-hexyloxy͒-p-phenylene vinylene͔ ͑MEH-PPV͒ and poly͓2,5-bis cholestanoxy-1,4 phenylene vinylene͔ ͑BCHA-PPV͒ blended with fullerenes. Absorption from the metastable charge-transferred state is probed by PIA; the modulated absorption spectrum causes changes in the real part of the index of refraction, ⌬n, which can be measured directly by PIR. The charge transfer gives rise to pronounced features in ⌬n, including vibrational structure in the mid-infrared, and broad spectral windows with negative ⌬n in the mid-and near-infrared. Our measurements over a wide spectral range ͑0.05 eV-1.9 eV͒ allow quantitative comparison of ⌬n obtained from PIR with that obtained from Kramers-Kronig transformation of the PIA data. We find good agreement throughout the infrared, indicating that our method for measuring ⌬n is useful as an analytical tool for optical characterization and for prediction of optical spectral ranges for nonlinear optical response.

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Ultrafast holography using charge-transfer polymers

Cited by 28 publications

References 15 publications

High‐Performance, Quantum Dot Nanocomposites for Nonlinear Optical and Optical Gain Applications

High‐Performance, Quantum Dot Nanocomposites for Nonlinear Optical and Optical Gain Applications

Nobel Lecture: Semiconducting and metallic polymers: The fourth generation of polymeric materials

Photo-induced changes in the complex index of refraction in conjugated polymer/fullerene blends

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