1,720,991 research outputs found
Comment on "Optical characterization of quantum dots entrained in microstructured optical fibers" [Physica E 26 (2005) 377-381]
No full textIn a recent paper, K.E. Meissner, C. Holton, W.B. Spillman Jr. [Physica E 26 (2005) 377] presented a study of the optical properties of colloidal CdSe/ZnS core-shell quantum dots entrained in a microstructured optical fiber. In particular, the authors claimed to have observed optical gain in this system through tight evanescent coupling between a probe light in the core of the fiber and photo-excited quantum dots in the cladding. I suggest that there are fundamental reasons, which are well investigated experimentally and documented, why such quantum dots cannot exhibit optical gain phenomena under continuous-wave excitation, as the authors suggest, and that the experimental results and interpretation do not address these issues, nor do they adequately justify the conclusions reached
Addendum to 'Highly efficient blue photoluminescence from colloidal lead-iodide nanoparticles' [Journal of Physics D. 39 (8) 1477, 2006]
No full textIn a recent paper (Finlayson C E and Sazio P J A 2006 J. Phys. D: Appl. Phys. 39 1477–80) we reported on the properties of colloidal lead (II) iodide nanoparticles, synthesized via a route using coordinating solvents. Our samples were characterized as having highly efficient and photostable photoluminescence in the blue region of the visible spectrum. Subsequent experiments show the observed behaviour of these nanoparticles during nucleation and ripening to be more complicated than originally reported and we believe that the observed photoluminescence may be related to extraneous factors, beyond the experimental methods as previously described
Strong exciton-photon coupling in a length tunable optical microcavity
No full textWe report the incorporation of thin films of a cyanine dye J aggregate into a versatile, length tunable, optical microcavity. The dense J-aggregate layers give an optical response that can be modified by embedding them at specific positions within heterostructures of dielectric and metal layers. The microcavities are composed of separate gold mirrors, which can be individually nanopositioned, and give sharp resonant modes in the red/near-infrared region of the spectrum. With the dye layer favorably placed, anticrossing behavior is observed as the cavity modes are successively swept through the absorption resonance. Large Rabi splittings of up to 170 meV are achieved at room temperature, agreeing well with predictions from a transfer-matrix model. These strongly coupled microcavities pave the way for microelectromechanical systems-integrated microdevices with tailored nonlinear optical properties
Highly efficient blue photoluminescence from colloidal lead-iodide nanoparticles
No full textWe report the synthesis of solvent-stabilized lead-iodide nanoparticles, using a convenient route involving coordinating solvents. The resultant colloids show strong absorption features in the ultraviolet region of the optical spectrum, which are consistent with the formation of semiconducting nanocrystals of lead (II) iodide. An effective-mass approximation model of quantum-confined states is in good agreement with the observed transition energies, giving strong indications of the particle morphologies and dimensions. Intense photoluminescence is also observed, with some spectral tuning possible with ripening time, giving a range of emission photon energies approximately spanning from 2.5 to 3.0 eV. We measure photo-stable luminescence quantum efficiencies of around 20% in solution, increasing to up to 30% if the coordinating ligand is exchanged for a Lewis-base capping layer. This demonstrates the potential for the utilization of lead-iodide nanocrystals in visible optoelectronics applications
Separation of photonic crystal modes using femtosecond time-of-flight measurements in a waveguide
No full textWhispering gallery mode emission at telecommunications-window wavelengths using PbSe nanocrystals attached to photonic beads
No full textWe report the selective chemical attachment of infrared emitting PbSe nanocrystal quantum dots onto micron-scale glass photonic beads. Upon optical excitation, photoluminescence from the shell of nanocrystals is seen to couple into the high-Q 'whispering gallery' modes of the bead via the evanescent optical field, resulting in a series of sharp peaks being observed at wavelengths of around 1550 nm. Theoretical modelling gives a close agreement with the data for angular modes corresponding to l ~ 120. This work demonstrates the potential of narrow-bandgap II–VI semiconductor nanocrystals for use in a wide range of telecommunications-window photonics applications
Surface enhanced Raman scattering using metal modified microstructured optical fibre substrates
No full textWe report the fabrication of metallic metamaterials using microstructured optical fibres as templates. The resulting fibres serve as excellent substrates for surface enhanced Raman spectroscopy and represent an exciting platform for in-fibre plasmonic devices
Infrared emitting PbSe nanocrystals for telecommunications window applications
No full textWe demonstrate the synthesis of PbSe nanocrystal quantum-dots using colloidal chemistry techniques [1]. These nanocrystals are found to have highly efficient, infrared luminescence from intrinsic quantum-confined states[2]. Based upon the sharp exciton absorption and photoluminescence (PL) emission spectra, a particle size distribution with a standard deviation of approximately 5% may be inferred. The wavelength of the PL may also be conveniently size-tuned in order to access the 1.3-1.5 microns "telecommunications window"[3]. The characterisation of PbSe nanocrystals in a variety of different optical environments is also reported. In particular, we examine the incorporation of nanocrystals into photonic structures, such as planar waveguides, and also cylindrical microcavities. In solution, these nanocrystals may also have use in infiltrating photonic structures for the purpose of achieving "liquid gain". The possibilities for using PbSe nanocrystals in a wide range of optoelectronic and telecommunications applications are discussed in the context of this work
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