AC Materials Inc.

Tarpon Springs, FL, United States

AC Materials Inc.

Tarpon Springs, FL, United States

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Volpi A.,University of Pisa | Cittadino G.,University of Pisa | Di Lieto A.,University of Pisa | Di Lieto A.,CNR Institute of Neuroscience | And 4 more authors.
Optical Engineering | Year: 2017

Optical cooling of solids, relying on annihilation of lattice phonons via anti-Stokes fluorescence, is an emerging technology that is rapidly advancing. The development of high-quality Yb-doped fluoride single crystals definitely led to cryogenic and sub-100-K operations, and the potential for further improvements has not been exhausted by far. Among fluorides, so far the best results have been achieved with Yb-doped LiYF4 (YLF) single crystals, with a record cooling to 91 K of a stand-alone YLF:10%Yb. We report on preliminary investigation of optical cooling of an LiLuF4 (LLF) single crystal, an isomorph of YLF where yttrium is replaced by lutetium. Different samples of 5% Yb-doped LLF single crystals have been grown and optically characterized. Optical cooling was observed by exciting the Yb transition in single-pass at 1025 nm and the cooling efficiency curve has been measured detecting the heating/cooling temperature change as a function of pumping laser frequency. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).


Favilla E.,CNR Institute of Neuroscience | Cittadino G.,University of Pisa | Veronesi S.,CNR Institute of Neuroscience | Tonelli M.,CNR Institute of Neuroscience | And 4 more authors.
Solar Energy Materials and Solar Cells | Year: 2016

Infrared to visible upconversion (UC) is a promising way to enhance the efficiency of silicon based solar cells. In this paper, the spectral conversion and recovery of sub-band gap photons of the solar spectrum, from NIR-IR to the VIS-NIR wavelength region, is investigated in two fluorides hosts doped with trivalent erbium ions (Er3+). The efficiency gain due to upconversion in silicon solar cells is compared for single crystal samples of BaY2F8:Er3+ and LiYF4:Er3+ in a dedicated upconverter solar cell device (UCSCD) with monochromatic excitation in the 1.5 µm spectral region. The highest external quantum efficiency due to upconversion was found for the UCSCD using the BaY2F8:30 at% Er3+ single crystal, reaching an EQE of 6.8±0.2% for (1.10±0.12)·105 W m−2 spectral irradiance at 1494 nm. We present a comprehensive spectroscopic study of the crystal samples also taking into account the effects of the different crystal symmetry as well as the different phonon energies. Our findings enable us to explain the higher efficiency of the BaY2F8:Er3+ compared to the LiYF4:Er3+ upconverter in terms of both static and dynamic properties. © 2016 Elsevier B.V.


Parisi D.,CNR Institute of Neuroscience | Parisi D.,University of Pisa | Veronesi S.,CNR Institute of Neuroscience | Veronesi S.,University of Pisa | And 6 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

In this work we present an overview of the best 2μm laser results obtained in Tm-doped fluoride hosts LiYF4(YLF), LiLuF4 (LLF) and BaY2F8 (BYF) and we report on the growth, spectroscopy and first laser test emission of a novel mixed material BaYLuF8 (BYLF), interesting as a variant of BYF material with a partial substitution of Y3+ ions by Lu3+. The novel host is interesting mainly because indications are that the mixed crystal would be sturdier than BYF. The addition of Lutetium would improve the thermo-mechanical properties going into the direction of high power applications, as suggest from works on YLF and its isomorph LLF. A detailed description of Czochralski growth of fluoride laser materials is provided, focusing on the growth parameters of the novel BYLF:Tm3+12% material grown. With regard of spectroscopy analysis, we report on the results obtained with BYLF host. Detailed absorption, fluorescence and lifetime measurements have been performed focusing on the 3H4 and 3F4 manifolds, the pumping and upper laser level. Moreover diode pumped CW laser emission at 2 μm has been achieved in BYLF: Tm3+12% sample obtaining a slope efficiency of about 28% with respect to the absorbed power. © 2013 SPIE.


Parisi D.,CNR Institute of Neuroscience | Veronesi S.,CNR Institute of Neuroscience | Volpi A.,University of Pisa | Gemmi M.,Italian Institute of Technology | And 3 more authors.
Journal of Physics D: Applied Physics | Year: 2014

A novel laser material BaYLuF8 (BYLF), doped with 12 at% of Tm3+, has been grown and optically investigated, in order to evaluate its potential performances as a 2 m laser. The BYLF crystal is interesting mainly because indications are that the mixed crystal would be sturdier than BaY2F,8 (BYF). The addition of lutetium would improve the thermo-mechanical properties of the host. Absorption, fluorescence and lifetime measurements have been performed in the temperature range 10-300 K focusing on the 3H4 and 3F4 manifolds, those involved in the laser scheme at 2 m. The Stark sublevels structure of Tm 3+ up to the 1D2 manifold has been figured out. Diode-pumped CW laser emission at 2 m has been achieved obtaining a slope efficiency of about 28% with respect to the absorbed power, by pumping along the Z-axis. A maximum output power of 240 mW was achieved by pumping along the favourable Y-axis, with an incident power of about 800 mW. © 2014 IOP Publishing Ltd.


Jeet J.,University of California at Los Angeles | Schneider C.,University of California at Los Angeles | Sullivan S.T.,University of California at Los Angeles | Rellergert W.G.,University of California at Los Angeles | And 5 more authors.
Physical Review Letters | Year: 2015

We report the results of a direct search for the Th229 (Iπ=3/2+←5/2+) nuclear isomeric transition, performed by exposing Th229-doped LiSrAlF6 crystals to tunable vacuum-ultraviolet synchrotron radiation and observing any resulting fluorescence. We also use existing nuclear physics data to establish a range of possible transition strengths for the isomeric transition. We find no evidence for the thorium nuclear transition between 7.3 eV and 8.8 eV with transition lifetime (1-2) s≲τ≲(2000-5600)s. This measurement excludes roughly half of the favored transition search area and can be used to direct future searches. © 2015 American Physical Society.


Turri G.,Rollins College | Turri G.,University of Central Florida | Gorman C.,University of Central Florida | Cassanho A.,AC Materials Inc. | And 2 more authors.
Journal of the Optical Society of America B: Optical Physics | Year: 2011

We grew oriented single crystals of BaYLuF8 and Nd:BaY 2F8 doped with Nd3+. An experimental investigation and comparison of the spectroscopic properties of the two crystals are presented to guide their use as lasing elements in solid-state lasers. The absorption and stimulated emission cross section of the Nd3+ 4F3/2 decay to the 4I9/2, 4I11/2 and 4I13/2 states, for light linearly polarized along the three principal axes, were obtained at room temperature. Nd:BaYLuF8 shows absorption and stimulated emission cross sections that are very similar to those of Nd:BaY2F 8, making it a good candidate for lasers. Because Nd:BaYLuF 8 is easier to grow than Nd:BaY2F8, it is a viable alternative as a laser medium. © 2011 Optical Society of America.


Cho J.-H.,University of Central Florida | Cho J.-H.,BdDisplays LLC | Bass M.,University of Central Florida | Bass M.,BdDisplays LLC | And 6 more authors.
IEEE/OSA Journal of Display Technology | Year: 2011

Up converters combined with GaAs based semiconductor light sources are described as having potential for emissive displays with very large color gamut and very high resolution. To enable such displays the efficiency and temporal response of the up converting materials were studied and are reported. High efficiency is shown to be possible by proper preparation and utilization of the up converters. Up conversion displays can operate with refresh rates as high as 240 Hz. Operation as either a visible or near infrared display is possible. © 2006 IEEE.


Spitzer M.B.,Photonic Glass Corporation | Jenssen H.P.,AC Materials Inc. | Cassanho A.,AC Materials Inc.
Solar Energy Materials and Solar Cells | Year: 2013

We describe an approach to solar downconversion in which a semiconductor is used for absorption, and substitutional rare earth ions are used for emission. The semiconductor would provide broad-band absorption, and the rare earth ions would provide emission of multiple photons by a cross relaxation process in a narrow wavelength band. The emitted photons are then absorbed by a solar cell formed from a low band gap semiconductor such as silicon. Er and Yb are suggested owing to strong emission at 980 nm which are useful when the down-converter is paired with silicon solar cells. The use of InGaN is proposed for the absorbing host semiconductor. © 2012 Elsevier B.V.


Spitzer M.B.,Photonic Glass Corporation | Jenssen H.,AC Materials Inc. | Cassanho A.,AC Materials Inc. | Goldberg B.,Boston University | Kitt A.,Boston University
Conference Record of the IEEE Photovoltaic Specialists Conference | Year: 2011

We describe the growth and characterization of Er-doped BaY 2F 8, KY 3F 10 and NaYF 4 crystals, intended as up and down converters to enhance the efficiency of single junction solar cells. Direct visual observation of upconversion is supported by photoluminescence spectroscopy indicating the presence of both upconversion and downconversion processes. Unlike powders, our samples are polished single crystals and are therefore especially useful for optical characterization and for the development of an understanding of the physics underlying upconversion and downconversion processes. The application of rare earth ion-doped crystals to Si solar cells is discussed, including limitations of rare earth absorption and ways to overcome these limitations. © 2011 IEEE.

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