scholarly journals Natural slab photonic crystals in centric diatoms

2019 ◽  
Author(s):  
Johannes W. Goessling ◽  
William P. Wardley ◽  
Martin Lopez Garcia
Keyword(s):  
Photonic Crystal ◽  
Photonic Crystals ◽  
Spectral Range ◽  
Near Infrared ◽  
Light Regulation ◽  
Visible Spectral Range ◽  
Mating Strategies ◽  
Unit Cell ◽  
Critical Parameters ◽  
Centric Diatom

AbstractNatural photonic crystals can serve in mating strategies or as aposematism for animals, but they also exist in some photosynthetic organisms, with potential implications for their light regulation. Some of the most abundant microalgae, named diatoms, evolved a silicate exoskeleton, the frustule, perforated with ordered pores resembling photonic crystals. Here we present the first combined experimental and theoretical characterization of the photonic properties of the diatom girdle, i.e. one of two structures assembling the frustule. We show that the girdle of the centric diatom Coscinodiscus granii is a well-defined slab photonic crystal, causing, under more natural conditions when immersed in water, a pseudogap for modes in the near infrared. The pseudogap disperses towards the visible spectral range when light incides at larger angles. The girdle crystal structure facilitates in-plane propagation for modes in the green spectral range. We demonstrate that the period of the unit cell is one of the most critical factors for causing these properties. The period is shown to be similar within individuals of a long-term cultivated inbred line and between 4 different C. granii cell culture strains. In contrast, the pore diameter had negligible effects upon the photonic properties. We hence propose that critical parameters defining the photonic response of the girdle are highly preserved. Other centric diatom species, i.e. Thalasiosira pseudonana, C. radiatus and C. wailesii, present similar unit cell morphologies with various periods in their girdles. We speculate that evolution has preserved the photonic crystal character of the centric girdle, indicating an important biological functionality for this clade of diatoms.

Near-infrared broadband cavity-enhanced sensor system for methane detection using a wavelet-denoising assisted Fourier-transform spectrometer

The Analyst ◽  
2018 ◽  
Vol 143 (19) ◽  
pp. 4699-4706 ◽  
Author(s):  
Kaiyuan Zheng ◽  
Chuantao Zheng ◽  
Zidi Liu ◽  
Qixin He ◽  
Qiaoling Du ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Spectral Range ◽  
Near Infrared ◽  
Wavelet Denoising ◽  
Visible Spectral Range ◽  
Sensor System ◽  
Trace Gas ◽  
Fourier Transform Spectrometer ◽  
Methane Detection

The majority of broadband cavity-enhanced systems are used to detect trace gas species in the visible spectral range.

scholarly journals Crystallization and visible–near-infrared luminescence of Bi-doped gehlenite glass

2018 ◽  
Vol 5 (12) ◽  
pp. 181667 ◽  
Author(s):  
M. Majerová ◽  
R. Klement ◽  
A. Prnová ◽  
J. Kraxner ◽  
E. Bruneel ◽  
...  
Keyword(s):  
Spectral Range ◽  
Near Infrared ◽  
Broad Band ◽  
Visible Spectral Range ◽  
Peak Temperature ◽  
Minor Amount ◽  
Glass Microspheres ◽  
Scanning Calorimetry ◽  
Crystallization Peak ◽  
High Temperature Xrd

Gehlenite glass microspheres, doped with a different concentration of Bi 3+ ions (0.5, 1, 3 mol%), were prepared by a combination of solid-state reaction followed by flame synthesis. The prepared glass microspheres were characterized from the point of view of surface morphology, phase composition, thermal and photoluminescence (PL) properties by optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and PL spectroscopy. The closer inspection of glass microsphere surface by SEM confirmed a smooth surface. This was further verified by XRD. The basic thermal characteristics of prepared glasses, i.e. T g (glass transition temperature), T x (onset of crystallization peak temperature), T f (temperature of the inflection point of the crystallization peak) and T p (maximum of crystallization peak temperature), were estimated from the DSC records. High-temperature XRD experiments in the temperature interval range 600–1100°C were also performed. The PL emission properties of prepared glasses and their polycrystalline analogues (glass crystallized at 1000°C for 10 h) were studied in the visible and near-infrared (NIR) spectral range. When excited at 300 nm, the glasses, as well as their polycrystalline analogues, exhibit broad emission in the visible spectral range from 350 to 650 nm centred at about 410–450 nm, corresponding to Bi 3+ luminescence centres. The emission intensity of polycrystalline samples was found to be at least 30 times higher than the emission of their glass analogues. In addition, a weak emission band was observed around 775 nm under 300 nm excitation. This band was attributed to the presence of a minor amount of Bi 2+ species in prepared samples. In the NIR spectral range, the broad band emission was observed in the spectral range of 1200–1600 nm with the maxima at 1350 nm. The chemistry of Bi and its oxidation state equilibrium in glasses and polycrystalline matrices is discussed in detail.

The Optical Spectra of a-Si:H and a-SiC:H Thin Films Measured by the Absolute Photothermal Deflection Spectroscopy (PDS)

2014 ◽  
Vol 213 ◽  
pp. 19-28 ◽  
Author(s):  
Zdenek Remes ◽  
Ravi Vasudevan ◽  
Karol Jarolimek ◽  
Arno H.M. Smets ◽  
Miro Zeman
Keyword(s):  
Thin Films ◽  
Spectral Range ◽  
Near Infrared ◽  
Energy Gap ◽  
Chemical Vapor ◽  
Visible Spectral Range ◽  
Localized States ◽  
Rf Plasma ◽  
Detection Range ◽  
The Absolute

The new absolute PDS setup allows to measure simultaneously the absolute values of the optical transmittance T, reflectance R and absorptance A spectra in the spectral range 280 2000 nm with the typical spectral resolution 10 nm in ultraviolet and visible spectral range and 20 nm in the near infrared region. The PDS setup provides the dynamic detection range in the optical absorptance up to 4 orders of magnitude using non-toxic liquid perfluorohexane Fluorinert FC72. Here we demonstrate the usability of this setup on a series of intrinsic as well as doped a-Si:H and a-SiC:H thin films deposited on glass substrates by radio frequency (RF) plasma enhanced chemical vapor deposition (CVD) from hydrogen, silane and methane under various conditions. The increase of the Tauc gap with increasing carbon concentration in intrinsic a-SiC:H was observed. The defect-induced localized states in the energy gap were observed in doped a-Si:H as well as undoped a-SiC:H below the Urbach absorption edge.

Enhancing Light-trapping and Efficiency of Solar Cells with Photonic Crystals

2007 ◽  
Vol 989 ◽  
Author(s):  
Rana Biswas ◽  
Dayu Zhou
Keyword(s):  
Solar Cells ◽  
Photonic Crystal ◽  
Photonic Crystals ◽  
Amorphous Silicon ◽  
Near Infrared ◽  
Light Trapping ◽  
Absorber Layer ◽  
Diffract Light ◽  
Major Route ◽  
Optical Wavelengths

AbstractA major route to improving solar cell efficiencies is by improving light trapping in solar absorber layers. Traditional light trapping schemes involve a textured metallic back reflector that also introduces losses at optical wavelengths. Here we develop alternative light trapping schemes with a-Si:H thin film solar cells, that do not use metallic components, thereby avoiding losses. We utilize low loss one-dimensional photonic crystals as distributed Bragg reflectors (DBR) at the backside of the solar cells. The DBR is constructed with alternating layers of crystalline Si and SiO2. Between the DBR and the absorber layer, there is a layer of 2D photonic crystal composed of amorphous silicon and SiO2. The 2D photonic crystal layer will diffract light at oblique angles, so that total internal reflection is formed inside the absorber layer. We have achieved enhanced light-trapping in both crystalline and amorphous silicon solar cells at near-infrared wavelengths where absorption lengths are very large. Very high absorption is achieved throughout optical wavelengths. The optical modeling is performed with a rigorous 3 dimensional scattering matrix approach where Maxwell¡¯s equations are solved in Fourier space.

scholarly journals Efficient near-infrared quantum cutting by cooperative energy transfer in Bi3TeBO9:Nd3+ phosphors

2022 ◽  
Author(s):  
T. Zhezhera ◽  
P. Gluchowski ◽  
M. Nowicki ◽  
M. Chrunik ◽  
A. Majchrowski ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Spectral Range ◽  
Near Infrared ◽  
Emission Spectra ◽  
Luminescent Properties ◽  
Infrared Emission ◽  
Fluorescence Decay ◽  
Visible Spectral Range ◽  
Visible Radiation ◽  
Quantum Cutting

Abstract An efficient near-infrared quantum cutting process by cooperative down-conversion of active Bi3+ and Nd3+ ions was demonstrated in Bi3TeBO9:Nd3+ phosphors. In particular, the near-infrared emission of Nd3+ ions enhanced by Bi3+ ions of a series of novel Bi3TeBO9:Nd3+ microcrystalline powders doped with Nd3+ ions in various concentrations was investigated. In order to investigate the luminescent properties of BTBO:Nd3+ powders, the excitation and emission spectra and the fluorescence decay time were measured and analyzed. In particular, the emission of Bi3TeBO9:Nd3+ at 890 and 1064 nm was excited at 327 nm (via energy transfer from Bi3+ ions) and at 586.4 nm (directly by Nd3+ ions). The highest intensity emission bands in near-infrared were detected in the spectra of Bi3TeBO9:Nd3+ doped with 5.0 and 0.5 at.% of Nd3+ ions upon excitation in ultraviolet and visible spectral range, respectively. The fluorescence decay lifetime monitored at 1064 nm for Bi3TeBO9:Nd3+ powders shows the single- or double-exponential character depending on the concentrations of Nd3+ ions. The possible mechanisms of energy relaxation after excitation Bi3TeBO9:Nd3+ powders in ultraviolet or visible spectral range were discussed. The investigated Bi3TeBO9:Nd3+ phosphors efficiently concentrate the ultraviolet/visible radiation in the near-infrared spectral range and can be potentially used as effective spectral converters. Graphical abstract

Enhanced Absorption in Amorphous Silicon Solar Cells Using Plasmonic and Photonic Crystals – Measurement and Simulation

2010 ◽  
Vol 1248 ◽  
Author(s):  
Benjamin Curtin ◽  
Rana Biswas ◽  
Vikram Dalal
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Photonic Crystal ◽  
Photonic Crystals ◽  
Amorphous Silicon ◽  
Near Infrared ◽  
Silicon Solar Cells ◽  
Back Reflectors ◽  
Back Reflector ◽  
Hole Arrays

AbstractWe develop experimentally and theoretically plasmonic and photonic crystals for enhancing thin film silicon solar cells. Thin film amorphous silicon (a-Si:H) solar cells suffer from decreased absorption of red and near-infrared photons, where the photon absorption length is large. Simulations predict maximal light absorption for a pitch of 700-800 nm for photonic crystal hole arrays in silver or ZnO/Ag back reflectors, with absorption increases of ~12%. The photonic crystal improves over the ideal randomly roughened back reflector (or the ‘4n2limit’) at wavelengths near the band edge. We fabricated metallic photonic crystal back-reflectors using photolithography and reactive-ion etching. We conformally deposited a-Si:H solar cells on triangular lattice hole arrays of pitch 760 nm on silver back-reflectors. Electron microscopy demonstrates excellent long range periodicity and conformal a-Si:H growth. The measured quantum efficiency increases by 7-8 %, relative to a flat reflector reference device, with enhancement factors exceeding 6 at near-infrared wavelengths. The photonic crystal back reflector strongly diffracts light and increases optical path lengths of solar photons.

scholarly journals Thermo-optical response of photonic crystal cavities operating in the visible spectral range

2013 ◽  
Vol 24 (31) ◽  
pp. 315204 ◽  
Author(s):  
Janik Wolters ◽  
Niko Nikolay ◽  
Max Schoengen ◽  
Andreas W Schell ◽  
Jürgen Probst ◽  
...  
Keyword(s):  
Photonic Crystal ◽  
Spectral Range ◽  
Optical Response ◽  
Visible Spectral Range ◽  
Photonic Crystal Cavities

Thermal Radiation From a Photonic Crystal of Silica-Particles

2011 ◽  
Author(s):  
Nozomi Ikemachi ◽  
Ryota Nakano ◽  
Shohei Kurogi ◽  
Koji Miyazaki
Keyword(s):  
Photonic Crystal ◽  
Photonic Crystals ◽  
Thermal Radiation ◽  
Diffuse Reflectance ◽  
Near Infrared ◽  
Three Dimensional ◽  
Mie Scattering ◽  
Silica Particles ◽  
Experimental Results ◽  
Ft Ir

Thermal radiation properties, such as reflectivity and emissivity, have been well modified by using a photonic crystal in this decade. In this paper we fabricated three-dimensional photonic crystals by self-assembled silica particles with 3 μm diameter. The close-packed hexagonal photonic crystal with defects is observed by SEM. The measured specular reflectance explained by modified Bragg’s law is measured with a diffuse reflectance by FT-IR. The near normally incident diffuse reflectance is measured by using paraboloidal mirrors to understand the diffuse reflection. We experimentally confirmed the strong diffuse reflectance in the near infrared regions. We numerically calculated reflectance of the three-dimensional photonic crystals by RCWA. The diffuse reflectance in near infrared is calculated only in the photonic crystal with defects. The numerically calculated diffuse reflectance is roughly explained by Mie scattering theory. The directional emissivity of the photonic crystal is measured by FT-IR with collimator. The normal emittance is suppressed in the photonic gap, but the directional emittance is enhanced in 30 degrees. The absorptance is numerically calculated to understand the experimental results. The numerical results show that the directional absorptance is increased in narrow direction. The directional sharp peak in 30 degrees is calculated although the monocrystalline photonic crystal is assumed in the numerical model. The effects of the defects in the photonic crystal on the emittance should be considered to explain the experimental results.

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