Refractive index evaluation of porous silicon using Bragg reflectors

Estrada‐Wiese, Denise; Río, J. A. del

doi:10.31349/revmexfis.64.72

Cited by 24 publications

(9 citation statements)

References 28 publications

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“…Generally, the loss in transmittance is caused not only by reflection but also by scattering. 42 The possibility of the scattering in porous thin films involves several factors: the air−AlOOH interface, the volume of the material, and the AlOOH−substrate interface. As a function of HWI temperature, the surface roughness of the film also increased; as observed from AFM analysis, the results were well corroborated with FE-SEM analysis.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Double-Sided, Omnidirectional γ-AlOOH Hierarchical Nanostructures: Imparting Enhanced Antireflective Properties with Self-Cleaning Capacity for Optical Devices

et al. 2021

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Herein, we have successfully developed an integrated strategy to develop antireflective coatings with self-cleaning capabilities based on periodic double-sided photonic γ-AlOOH nanostructures to transmit maximum incident light photons. Interfacial reflections are instinctive and one of the fundamental phenomena occurring at interfaces owing to refractive index mismatch. The eradication of such undesirable light reflection is of significant consideration in many optical devices. A systematic approach was carried out to eradicate surface reflection and enhance optical transmission by tailored γ-AlOOH nanostructures. The γ-AlOOH photonic nanostructures with subwavelength features exhibited a gradient index, which almost eliminated the refractive index mismatch at the interface. Optical transmittance of 97% was achieved in the range of 350–800 nm at normal incidence compared to uncoated glass (89%). A multilayer model approach was adopted to extract the effective refractive index of the coating, which showed a graded index from the top to the bottom surface. Further, to fully comprehend the optics of these nanostructures, the omnidirectional (20–70°) antireflective property has been explored using variable-angle specular reflectance spectroscopy. The hierarchical γ-AlOOH nanostructures exhibited only ∼1.3% reflectance at the lower incident angle in the visible spectra and an average reflectance of ∼7.6% up to an incident angle of 70°. Moreover, the hierarchical nanostructures manifested contact angle (CA) >172° and roll-off angle (RA) <1° with excellent self-cleaning performance. Furthermore, the abrasion resistance of the coating is discussed in detail, which displayed a good resistance against sand erosion. Significantly, the photovoltaic performance of the coated modules exhibited a relative enhancement of ∼17% in efficiency, which is attributed to the efficient coupling of light rays. Thus, the integration of the antireflection (AR) property with self-cleaning ability can provide a cost-effective energy solution for optoelectronic devices, display devices, and thin-film optics.

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Section: ■ Results and Discussionmentioning

confidence: 99%

“…Generally, the loss in transmittance is caused not only by reflection but also by scattering . The possibility of the scattering in porous thin films involves several factors: the air–AlOOH interface, the volume of the material, and the AlOOH–substrate interface.…”

Section: Resultsmentioning

confidence: 99%

Double-Sided, Omnidirectional γ-AlOOH Hierarchical Nanostructures: Imparting Enhanced Antireflective Properties with Self-Cleaning Capacity for Optical Devices

et al. 2021

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“…The reflectance is given by = | | 2 and the transmittance by = | | 2 with = Re 0 ∕Re for TE polarization and = Re ∕Re 0 for TM polarization. The complex refractive index of the porous layers were obtained through the Bruggeman's effective medium theory, which has been reported to adequately reproduce the optical parameters of PS [16,32,33].…”

Section: Theorymentioning

confidence: 99%

Optimization of wide-band quasi-omnidirectional 1-D photonic structures

Castillo-Gallardo,

Puente-Díaz,

Ariza-Flores

et al. 2021

Preprint

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We have designed, optimized, fabricated and characterized highly reflective quasi-omnidirectional (angular range of 0 − 60 • ) multilayered structures with a wide spectral range. Two techniques, chirping (a continuous change in thicknesses) and stacking of Bragg-type sub-structures, have been used to enhance the reflectance with minimum thickness for a given pair of refractive indices. Numerical calculations were carried out employing the transfer matrix method and we optimized the design parameters to obtain maximal reflectance averaged over different spectral ranges for all angles. We fabricated some of the optimized structures with porous silicon dielectric multilayers with low refractive contrast and compared their measured optical properties with the calculations. Two chirped structures with thicknesses 21.6 m and 60.4 m, resulting in quasi omnidirectional mirrors with bandwidths of 360 nm and 1800 nm, centered at 1160 nm and 1925 nm respectively have been shown. In addition, we fabricated a stacked sub-Bragg mirror structure with a quasi omnidirectional bandwidth of 1800 nm (centered at 1850 nm) and a thickness of 41.5 m, which is almost two third (in thickness) of the chirped structure. Thus, our techniques allowed us to obtain relatively thin quasi-omnidirectional mirrors with wide bands over different wavelength ranges. Our analysis techniques can be used for the optimization of the reflectance not only in multilayered PS systems with different refractive index contrasts but also for systems with other types of materials with low refractive index contrast. The present study could also be useful for obtaining omnidirectional dielectric mirrors in large spectral regions using different materials, flat focusing reflectors, thermal regulators, or, if defects are included, as filters or remote chemical/biosensors with a wide angular independent response.

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“…They are formed of multilayers of alternating refractive indices and can be easily fabricated with different materials such as semiconductors (groups II-VI, III-V and IV), oxides, polymers and metal-dielectric structures [5]. Because of the easy manner to change its porosity, by modifying the fabrication conditions [6][7][8], and hence its refractive index values, porous silicon (PS) is an excellent material to fabricate 1D PCs.…”

Section: Introductionmentioning

confidence: 99%

Temperature distribution inside a porous silicon photonic mirror

Estrada‐Wiese¹,

Ortega²,

Río³

2021

J. Phys. D: Appl. Phys.

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Photonic devices require precise and high-cost procedures to evaluate their performance which is related to their temperature increase. The fundamental understanding of thermal phenomena, ergo measurement of temperature, inside radiation controlling devices is of great relevance to study their performance. In this paper, we carry out a comprehensive campaign of experiments to study the temperature profile inside a porous silicon multilayer 1D photonic structure by using a thermographic camera. In particular, we have analyzed broad-range reflective devices and found that the electromagnetic radiation does not travel beyond the photonic structure showing a clear maximum inside of it. We have compared this result with a pure silicon wafer under the interaction with the same radiation. To compare these samples, we used a normalization procedure that can be implemented on many microstructured devices to simplify their performance evaluation.

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Refractive index evaluation of porous silicon using Bragg reflectors

Cited by 24 publications

References 28 publications

Double-Sided, Omnidirectional γ-AlOOH Hierarchical Nanostructures: Imparting Enhanced Antireflective Properties with Self-Cleaning Capacity for Optical Devices

Double-Sided, Omnidirectional γ-AlOOH Hierarchical Nanostructures: Imparting Enhanced Antireflective Properties with Self-Cleaning Capacity for Optical Devices

Optimization of wide-band quasi-omnidirectional 1-D photonic structures

Temperature distribution inside a porous silicon photonic mirror

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