Anderson localization of light in a colloidal suspension (TiO<sub>2</sub>@silica)

Jiménez‐Villar, Ernesto; Silva, Iran F. da; Mestre, Valdeci; Oliveira, Paulo César de; Faustino, Wagner M.; Sá, Gilberto F. de

doi:10.1039/c5nr07540h

Cited by 27 publications

(39 citation statements)

References 42 publications

(61 reference statements)

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“…Notice that for large depths→, the influence of the input surface (internal reflection) becomes insignificant. For comparison, the propagation experiment was also performed for a sample in the diffusive regime with lower [NPs]=[14x10 10 NPs ml -1 ] [6]. Figure 2a (open square) and 2c reveal, as expected, that both the integrated intensity (I()) and effective width (ωeff), respectively, are insensitive to the incidence angle.…”

Section: Propagation Experimentsmentioning

confidence: 58%

“…Thereby, owing to the inhomogeneity at microscopic scale, localized and extended modes, coming from different regions with klT values lower and higher than unity, respectively, can coexist in a same sample. This picture is what we have called in our previous works as the localization transition regime [6,7,24,43,54]. In this way, the average klT value, extracted from the coherent backscattering experiment, would not provide a definitive criterion for the critical phase of localization transition.…”

Section: Backscattering Experimentsmentioning

confidence: 90%

“…TiO2@Silica NPs with a homogeneous silica shell of 40 nm thickness, synthesized by an improved strobe method [25,26], were dispersed in ethanol solution at [140x10 10 NPs ml -1 ]. For comparison, a sample with lower [NPs] in the diffusive regime [14 x10 10 NPs ml -1 ] [6] was also prepared.…”

Section: Sample Preparationmentioning

confidence: 99%

“…The latter can be understood as that, an increase in the incidence angle provokes an increase in the density of superficial localized states by the increase of the internal reflection [42]. In turn, an increase in the density of superficial localized states leads to an increase of the light-matter interaction [1,6], which would result in an increase of absorption ((lIn0) − ) and refractive index (neff0) near the input border. Of course, lIn0 must be still longer than the microscopic coherence length, Coh ≤ lIn0, for the absorption not to dominate the localization phenomenon.…”

Section: Absorption Experimentsmentioning

confidence: 99%

“…Of course, lIn0 must be still longer than the microscopic coherence length, Coh ≤ lIn0, for the absorption not to dominate the localization phenomenon. For comparison, FAP measurements were also performed for a sample in the diffusive regime with lower [NPs]=[14x10 10 NPs ml -1 ] [6], reveling that the FAP value is insensitive to the incidence angle (supplementary material, figure 3Sg). In the above experiments, we show a decrease of transmitted intensity and infer an increase of localization and absorption near the input border as the incidence angle is increased.…”

Section: Absorption Experimentsmentioning

confidence: 99%

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Anomalous transport of light at the phase transition to localization: strong dependence with incident angle

et al. 2018

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Disordered optical media have seen a growing interest in recent year due to their potential applications in solar collectors, random lasers, light confinement and other advanced photonic functions. This paper studies the transport of light for different incidence angles in a strongly disordered optical medium composed by core-shell TiO2@Silica nanoparticles suspended in ethanol solution. A decrease of optical conductance and an increase of absorption near the input border are reported when the incidence angle increases. The specular reflection, measured for the photons that enter the sample, is lower than the effective internal reflection undergone by the coherently backscattered photons in the exact opposite direction, indicating a non-reciprocal propagation of light. This study represents a novel approach in order to understand the complex physics involved at the phase transition to localization.

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Section: Propagation Experimentsmentioning

confidence: 58%

Section: Backscattering Experimentsmentioning

confidence: 90%

Section: Sample Preparationmentioning

confidence: 99%

Section: Absorption Experimentsmentioning

confidence: 99%

Section: Absorption Experimentsmentioning

confidence: 99%

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Anomalous transport of light at the phase transition to localization: strong dependence with incident angle

et al. 2018

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Longitudinal Optical Fields in Light Scattering from Dielectric Spheres and Anderson Localization of Light

Escalante

Skipetrov

2017

Annalen der Physik

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Recent research has shown that coupling between point scatterers in a disordered medium by longitudinal electromagnetic fields is harmful for Anderson localization of light. However, it has been unclear if this feature is generic or specific for point scatterers. The present work demonstrates that the intensity of longitudinal field outside a spherical dielectric scatterer illuminated by monochromatic light exhibits a complicated, nonmonotonous dependence on the scatterer size. Moreover, the intensity is reduced for a hollow sphere, whereas one can adjust the parameters of a coated sphere to obtain a relatively low longitudinal field together with a strong resonant scattering efficiency. Therefore, random arrangements of structured (hollow or coated) spheres may be promising three-dimensional disordered materials for reaching Anderson localization of light.

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Polydispersed Powders (Nd³⁺:YVO₄) for Ultra Efficient Random Lasers

Wetter

Giehl

Butzbach

et al. 2017

Part & Part Syst Charact

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inherent cost advantages become attractive for the large majority of applications.In order to overcome the problems of random lasers associated to nondirectional output and lack of efficiency, the main approach has been to choose lowdimensional random lasers. 1D fiber random lasers are well suited for this purpose and have achieved up to several watts of continuous output. [10] 2D distributed feedback (DFB) lasers have demonstrated highly efficient and directional output in the microjoule range. [11] These low-dimensional random lasers are generally quite large (like in the case of random fiber lasers) and require sophisticated production methods that are in stark contrast to the simplicity and practicality of the 3D random laser production.Noginov and co-workers have studied the dependence of random laser emission in neodymium doped powders (Nd 0.5 La 0.5 Al 3 (BO 3 ) 4 ) on the particle size, the powder volume density, and the pump spot size. [12,13] Best reported efficiency was below half a percent. An impediment for increasing the efficiency is the surface reflectivity of the compacted powders. The bulk reflection coefficient of Nd 0.5 La 0.5 Al 3 (BO 3 ) 4 at λ = 532 nm for medium to high powder density is ≈0.7. [13] Using a fiber-coupled random laser, where the pump fiber terminates deep inside the scattering medium in order to deliver the pump energy directly into the gain volume without reflection loss at the surface, Noginov et al. achieved a higher efficiency of ≈0.7%. [14] Azkargorta et al. achieved 20% and 42% slope efficiencies with respect to pump power using Nd: yttrium aluminium garnet (YAG) and Nd 3 Ga 5 O 12 crystal powders. [15,16] The stimulated random laser (RL) emission of these rare earth doped powder pellets comes in the form of a Lambertian emission with a linewidth that decreases around laser threshold and becomes much smaller than typical amplified spontaneous emission (ASE). [17] Output power also shows a typical laser threshold and slope efficiency. As we have shown for yttrium vanadate doped with neodymium (Nd:YVO 4 ), the emission decay after a pump pulse follows two different exponentials corresponding to a fast laser emission decay of a few microseconds and a slower fluorescence emission decay which is shorter than the intrinsic decay time, which should amount to 73 µs for 1.33 mol% neodymium doping concentration, because of upconversion. [18] We therefore expected some decrease in laser efficiency due to energy transfer upconversion.Random lasers hold the potential for cheap, coherent light sources that can be miniaturized and molded into any shape with several other added benefits such as speckle-free imaging; however, they require improvements specifically in terms of efficiency. This paper details for the first time a strategy for increasing the efficiency of a random laser that consists in using smaller particles, trapped between large particles to serve as absorption and gain centers whereas the large particles control mainly the light diffusion into the sample. Measurements...

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Anderson localization of light in a colloidal suspension (TiO₂@silica)

Cited by 27 publications

References 42 publications

Anomalous transport of light at the phase transition to localization: strong dependence with incident angle

Anomalous transport of light at the phase transition to localization: strong dependence with incident angle

Longitudinal Optical Fields in Light Scattering from Dielectric Spheres and Anderson Localization of Light

Polydispersed Powders (Nd³⁺:YVO₄) for Ultra Efficient Random Lasers

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Anderson localization of light in a colloidal suspension (TiO2@silica)

Cited by 27 publications

References 42 publications

Anomalous transport of light at the phase transition to localization: strong dependence with incident angle

Anomalous transport of light at the phase transition to localization: strong dependence with incident angle

Longitudinal Optical Fields in Light Scattering from Dielectric Spheres and Anderson Localization of Light

Polydispersed Powders (Nd3+:YVO4) for Ultra Efficient Random Lasers

Contact Info

Product

Resources

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Anderson localization of light in a colloidal suspension (TiO₂@silica)

Polydispersed Powders (Nd³⁺:YVO₄) for Ultra Efficient Random Lasers