Ullrich Photonics LLC

OH, United States

Ullrich Photonics LLC

OH, United States
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Ullrich B.,National Autonomous University of Mexico | Ullrich B.,Ullrich Photonics LLC | Singh A.K.,National Autonomous University of Mexico | Barik P.,National Autonomous University of Mexico | And 2 more authors.
Optics Letters | Year: 2015

The intrinsic photoluminescence Stokes shift, i.e., the energy difference between optical band gap and emission peak, of 350 μm thick semi-insulating GaAs wafers is found to be 4 meV at room temperature. The result is based on the determination of the optical bulk band gap from the transmission trend via modified Urbach rule whose result is confirmed with the transmission derivative method. The findings reveal the detailed balance of the optically evoked transitions and disclose the intrinsic link between Stokes shift and the Urbach tail slope parameter. © 2015 Optical Society of America.


Ullrich B.,Ullrich Photonics LLC | Ullrich B.,Air Force Research Lab | Brown G.J.,Air Force Research Lab
Review of Scientific Instruments | Year: 2012

Although known for more than twenty years, there is limited information in the literature regarding the experimental parameters of lock-in based phase sensitive emission detection in conjunction with Fourier spectrometers. For this technique - also known as double modulation spectroscopy - we present a guideline for parameter optimization by measuring the photoluminescence of InSb:Te at cryogenic temperatures. © 2012 American Institute of Physics.


Ullrich B.,National Autonomous University of Mexico | Ullrich B.,Ullrich Photonics LLC | Xi H.,Bowling Green State University | Wang J.S.,Air Force Research Lab
Applied Physics Letters | Year: 2016

The exposure of colloidal 2 nm PbS quantum dots to growing continuous wave laser excitation at 532 nm increases the photoluminescence intensity with the square root of the optical stimulus. The results herein in conjunction with previous findings [B. Ullrich and H. Xi, Opt. Lett. 38, 4698 (2013)] advocate the square root trend to be the general limiting function for photo-carrier transport and emission of optically excited nano-sized materials. We further show that the excitation of one electron-hole pair per quantum dot defines the saturation threshold for photoluminescence intensity and dynamic band filling. © 2016 AIP Publishing LLC.


Ullrich B.,National Autonomous University of Mexico | Ullrich B.,Ullrich Photonics LLC | Xi H.,Bowling Green State University | Wang J.S.,Air Force Research Lab
Journal of Applied Physics | Year: 2014

Increase in continuous wave laser excitation (6 W/cm2 to 120 W/cm2) of colloidal PbS quantum dots in the strongly quantized regime (diameters 2.0 nm and 4.7 nm) deposited on semi-insulating GaAs and glass causes a clear blue shift (0.019 eV and 0.080 eV) of the emission spectra. Proof of the applicability of a dynamic three-dimensional band filling model is the significance of the presented results and demonstrates the effective electronic coupling in quantum dot arrays similar to superlattices. The work also reveals the influence of quantum dot sizes on photo-doping effects. © 2014 AIP Publishing LLC.


Shahi P.K.,Banaras Hindu University | Singh A.K.,National Autonomous University of Mexico | Rai S.B.,Banaras Hindu University | Ullrich B.,National Autonomous University of Mexico | Ullrich B.,Ullrich Photonics LLC
Sensors and Actuators, A: Physical | Year: 2014

The Eu(DBM)3Phen complex has been synthesized and dispersed in poly(methyl methacrylate) and polyvinyl alcohol matrices in order to explore its versatile applicability. Excitation spectroscopy monitored at 611 nm show intense ultraviolet-blue spectra (∼250 to 450 nm) pointing to efficient energy transfer from the organic ligands to the central Eu3+ ion. The excellent photoluminescence properties, i.e.; broad-band excitation spectra, sharp and intense emission, and long lifetime open the door for appealing multi-applications such as temperature sensing, ultraviolet light detection, and laser applications. Photoluminescence based temperature sensing with a sensitivity of up to 1.75% per K is demonstrated for the temperature range of 50-318 K, and additionally, ultraviolet radiation detection is demonstrated, whilst impinging ultraviolet intensities as weak as 96 nW/cm2 can be detected. The work further reports several essential device characteristics, such as emission dependence on impinging excitation intensity, sensor stability, and photoluminescence response times. Finally, by increasing the optical excitation, amplification in spontaneous emission and decrease of full width at half maximum take place, pointing to stimulated emission. This feature, in conjunction with the stimulated emission cross-section of 3.24 × 10-20 cm2, which is comparable to the Nd-Glass laser, suggests the suitability of the investigated lanthanide-polymer merger for laser realizations. © 2014 Elsevier B.V.


Barik P.,National Autonomous University of Mexico | Singh A.K.,National Autonomous University of Mexico | Ullrich B.,National Autonomous University of Mexico | Ullrich B.,Ullrich Photonics LLC
Physica Scripta | Year: 2015

Reflectance and absorbance of colloidal 2.5 nm PbS quantum dots were coincidentally measured under the presence of moderate magnetic fields below one Tesla. The work provides further insight to the optical and magneto-optical properties of quantum dots by revealing disconnect of band gap data collected in different experimental geometries and by the demonstration of reflective magneto-optical devices addressable with weak magnetic fields. © 2015 The Royal Swedish Academy of Sciences.


Singh A.K.,National Autonomous University of Mexico | Shahi P.K.,Banaras Hindu University | Rai S.B.,Banaras Hindu University | Ullrich B.,National Autonomous University of Mexico | Ullrich B.,Ullrich Photonics LLC
RSC Advances | Year: 2015

By synthesizing Y(1.9-2x)Yb0.1Er2xO3, Y(0.95-x)Yb0.05ErxVO4 and Y(0.95-x)Yb0.05ErxPO4 phosphors, with phonon frequency maxima at 560, 826 and 1050 cm-1, respectively, we present the impact of phonon energy and crystal structure of the host matrix on upconversion and temperature sensing behavior. The spectral upconversion characteristics of all three phosphors reveal noticeable differences. The temperature sensing studies reveal that the phosphors have maximum sensitivity at ∼490 K, which is found to be highest (0.0105 K-1) in Y0.947Yb0.05Er0.003VO4 followed by Y1.894Yb0.1Er0.006O3 and Y0.947Yb0.05Er0.003PO4 phosphors. We found that the temperature sensitivity basically depends on the intensity ratio of two thermally coupled emission bands, 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2, of Er3+. Further, the intensity ratio depends on phonon energy of the host lattice, crystal structure, surface quenching centers and the temperature dependence of non-radiative decay rate. This journal is © The Royal Society of Chemistry 2015.


Shahi P.K.,Banaras Hindu University | Singh A.K.,National Autonomous University of Mexico | Singh S.K.,Banaras Hindu University | Rai S.B.,Banaras Hindu University | And 2 more authors.
ACS Applied Materials and Interfaces | Year: 2015

We synthesized the Eu(TTA)3Phen complex and present herein a detailed study of its photophysics. The investigations encompass samples dispersed in poly(vinyl alcohol) and in ethanol in order to explore the versatile applicability of these lanthanide-based materials. Details upon the interaction between Eu, TTA, and the Phen ligands are revealed by Fourier transform infrared and UV-visible absorption, complemented by steady state and temporally resolved emission studies, which provide evidence of an efficient energy transfer from the organic ligands to the central Eu3+ ion. The material produces efficient emission even under sunlight exposure, a feature pointing toward suitability for luminescent solar concentrators and UV light sensing, which is demonstrated for intensities as low as 200 nW/cm2. The paper further promotes the complex's capability to be used as luminescence-based temperature sensor demonstrated by the considerable emission intensity changes of ∼4.0% per K in the temperature range of 50-305 K and ∼7% per K in the temeperature range 305-340 K. Finally, increasing the optical excitation causes both spontaneous emission amplification and emission peak narrowing in the Eu(TTA)3Phen complex dispersed in poly(vinyl alcohol) - features indicative of stimulated emission. These findings in conjunction with the fairly large stimulated emission cross-section of 4.29 × 10-20 cm2 demonstrate that the Eu(TTA)3Phen complex dispersed in poly(vinyl alcohol) could be a very promising material choice for lanthanide-polymer based laser architectures. (Graph Presented). © 2015 American Chemical Society.


Singh A.K.,National Autonomous University of Mexico | Barik P.,National Autonomous University of Mexico | Ullrich B.,National Autonomous University of Mexico | Ullrich B.,Ullrich Photonics LLC
Applied Physics Letters | Year: 2014

We observed changes of the transmitted monochromatic light passing through a colloidal PbS quantum dot film on glass owing to an applied moderate (smaller than 1 T) magnetic field under ambient conditions. The observed alterations show a square dependence on the magnetic field increase that cannot be achieved with bulk semiconductors. The findings point to so far not recognized application potentials of quantum dots. © 2014 AIP Publishing LLC.


Ullrich B.,National Autonomous University of Mexico | Ullrich B.,Ullrich Photonics LLC | Barik P.,National Autonomous University of Mexico | Singh A.K.,National Autonomous University of Mexico | And 2 more authors.
Optical Materials Express | Year: 2015

We report photo-dynamically provoked photoluminescence blue shifts up to ~8 meV of oleic acid capped 2.5 nm PbS quantum dots in toluene at room temperature. Exposing the solution to pulsed laser (26 ps, 10 Hz) emissions at 532 nm and 1064 nm, the photo-induced band gap increase is evoked by single and two-photon transitions, respectively. The emission peak blue shifts, recorded in reflection and transmission geometries, show a 2/3 power dependence on the optical stimulus gain, rendering the Burstein-Moss shift to be the underlying inherent n-type doping effect in the quantized colloid. © 2015 Optical Society of America.

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