July 29, 2014

Meliora - Ever Better

AS&E Graduate Student Association
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July 2014
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UR SPIE Colloquium Summer Series

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July 1, 2014

On Tuesday, July 1st the UR SPIE student chapter will be continuing its Summer Colloquium series. Please bring your lunch and come listen to our next presentation! Snacks and beverages will be provided.

Who: Patrice Tankam
What: Multiple-Wavelength Digital Holography and Applications
Date: 7/1/2014
Time: 11:30 am - 12:30 pm
Where: Sloan Auditorium (Goergen 101)
Abstract: Since its discovery in 1947 by Denis Gabor, Holography was shown to be a powerful tool to perform “real” 3D imaging and optical metrology. The development of high-resolution CCDs and powerful processors during the last decades opened new opportunities to apply digital holography in different domains. Digital holography combines the interferometric recording of the light scattered from the object and the back-propagation computation of the interference pattern to retrieve the 3D information of the object. Most of the recent developments and accomplishments in digital holography were based on a single-wavelength configuration. However, a multiple-wavelength is necessary to obtain the true color of the object or the absolute value of the measurement. This presentation will focus on my contribution in multiple-wavelength digital holography applied in several projects (aerodynamic flow visualization, mechanics, electronics, etc).
 
The SPIE Student Summer Colloquium Series is a weekly event to be held on Tuesdays from June to August. If you are a student willing to give a talk, please send an email to urspie@gmail.com with your talk title, a short abstract, and preferred talk date.
Do you want to know what your peers are doing in their research? Want to network with people from the same field? Would you like to benefit from scholarships and conference discounts? Well, then join SPIE now! Just go to spie.org to register to become a student member of the U of Rochester chapter or send an email to urspie@gmail.com if you have any questions.
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GSS Career Development Seminar

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July 2, 2014

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UR SPIE Summer Colloquium Series

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July 8, 2014

On Tuesday, July 8st the UR SPIE student chapter will be continuing its Summer Colloquium series. Please bring your lunch and come listen to our next presentation! Snacks and beverages will be provided.
Who: Steve Head
What: Arbitrary Spatially-Varying Polarization State Generator for Deep Sub-Wavelength Metrology​
Date: 7/8/2014
Time: 11:30 am – 12:30 pm
Where: Sloan Auditorium (Goergen 101)
Abstract: The lithography industry makes use of a wide array of tools for metrology of their nano-scale structures. Scatterometry is one such method in which the scattered light from a periodic test structure is compared with theoretical results from Rigorous Coupled Wave Analysis in order to back-out structure parameters such as critical dimension, film thicknesses, and sidewall angle. Current scatterometry methods could possibly be improved by using a focused beam to acquire angular scatter information in a single measurement and by tailoring the input polarization to make the output more sensitive to small deviations. This talk will focus on the polarization generator I helped build and how it can be used to maximize the ability of a scatterometry system to back-out structure parameters.
The SPIE Student Summer Colloquium Series is a weekly event to be held on Tuesdays from June to August. If you are a student willing to give a talk, please send an email to urspie@gmail.com with your talk title, a short abstract, and preferred talk date.
Do you want to know what your peers are doing in their research? Want to network with people from the same field? Would you like to benefit from scholarships and conference discounts? Well, then join SPIE now! Just go to spie.org to register to become a student member of the U of Rochester chapter or send an email to urspie@gmail.com if you have any questions.
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Mendon Ponds Hiking Trip

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July 12, 2014

GSA is coordinating a hiking trip to Mendon Ponds Park on Saturday, July 12th. We'll meet up at the park at 1 pm and stay until around 4 pm. All levels of hikers are welcome, and feel free to invite friends! Check out more information here: http://www.rochester.edu/gsa/gsa-mendon-ponds-park-hike/

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UR SPIE Colloquium Summer Series

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July 15, 2014

On Tuesday, July 15th the UR SPIE student chapter will be continuing its Summer Colloquium series. Please bring your lunch and come listen to our next presentation! Snacks and beverages will be provided.

                   Who: Robin Sharma
                   What: Two-photon fluorescence imaging of the retina in the living eye using adaptive optics
                   Date: 7/15/2014
                   Time: 11:30 am – 12:30 pm
                   Where: Sloan Auditorium (Goergen 101)
Abstract: Adaptive optics scanning laser ophthalmoscopy (AOSLO) permits diffraction-limited imaging of microscopic structures in the retina in living eyes. Thanks to various advances in system design and image registration software, functional imaging of different cell classes in the retina is within reach. Two-photon fluorescence imaging has a number of advantages for retinal imaging. All cells in the retina fluoresce with appropriate infrared two-photon excitation, offering the possibility of imaging every class of retinal cell, even those that are transparent in visible light. It also allows the study of molecular species whose excitation regime is in the ultraviolet, a region of the spectrum that is inaccessible in reflectance and single photon fluorescence imaging because it lies outside the transmittance spectrum of the ocular media. Additionally, it allows functional as well as structural imaging by monitoring molecular changes that are invisible with conventional imaging methods. A two-photon adaptive optics scanning light ophthalmoscope has been developed for imaging living, anaesthetized primates. An ultrashort pulsed laser (~ 55 fs pulse-width) with a tunable central wavelength was used to excite two-photon fluorescence. Consistent with measurements made in excised retina, fluorescence emission was detected throughout the retina in vivo although the strongest autofluorescence signal originated from near the photoreceptor layer. Two-photon images of individual cells and other recognizable structures were obtained in multiple retinal layers such as the nerve fiber layer, individual rods as well as cones and retinal pigment epithelial cells. Also, the time-course of fluorescence from individual photoreceptor cells provides clues about the molecules that might be responsible for this autofluorescence. This is an important step towards noninvasively monitoring functional activity in individual retinal layers. 
The SPIE Student Summer Colloquium Series is a weekly event to be held on Tuesdays from June to August. If you are a student willing to give a talk, please send an email to urspie@gmail.com with your talk title, a short abstract, and preferred talk date.
Do you want to know what your peers are doing in their research? Want to network with people from the same field? Would you like to benefit from scholarships and conference discounts? Well, then join SPIE now! Just go to spie.org to register to become a student member of the U of Rochester chapter or send an email to urspie@gmail.com if you have any questions.
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GSS Wine Tour

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July 20, 2014

GSS Wine Tour
AS&E students have been invited to join the Graduate Student Society (URMC equivalent of GSA) wine tour! It will be taking place this Sunday, July 20th, from 9 am-4 pm. This event is sponsored and subsidized by GSS. The tour will be $30 per person, which includes admissions to 3 finger lake wineries, lunch, and bus transportation from URMC to the wineries and back to URMC. If you are interested, please sign up at the School of Medicine & Dentistry Office for Graduate Education and Postdoctoral Affairs (G-9556) with Amy Perazzo and feel free to sign up your family and friends. Only 35 tickets will be sold, so act soon!

GSS Wine Tour

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M.S. Defense Seminar - Dept. of Biomedical Engineering

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July 21, 2014

Variation Seen in Walking Patterns of a Healthy Population and the Impact of Data Collection Methods on Uncertainty and Cost of Biomechanical Modeling

 by Molly Zapkin

Co-supervised by:  Prof. Amy Lerner and Prof. Paul Funkenbusch

Monday, July 21, 2014

2:00 pm

River Campus

Hopeman Bldg., Room 224

 Abstract

Biomechanical models are often used in research to simulate complex situations that may be difficult to capture in an in-vivo setting. The two goals of this research were (1) to identify the variability in the walking patterns seen within and between subjects during normal walking and (2) to develop a methodology that can be applied to any type of model that allows the researcher to assess the model uncertainty in relation to the cost of data collection.  Intra-class correlation coefficients and 95% bootstrap confidence intervals were used to assess the intra and inter subject variability, respectively.  The variability analysis provides results that can be used when developing gait data collection protocols to obtain necessary model inputs. The methodology for assessing the uncertainty in the model provides researchers with a way to justify how they utilize their resources in terms of data collection.

 

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GSA Coffee Hour

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July 23, 2014

GSA Coffee Break
We're starting a monthly coffee hour! Take a break from studying/research and join us on Wednesday morning, July 23rd in the Hawkins-Carlson Room in Rush Rhees library. We'll have coffee, tea, juice, and breakfast foods from 9-10:30 am. Stop by for a few minutes or stay the whole time and meet some other grad students! This is also a great time to meet the GSA officers and let us know any ideas you might have!

 

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UR SPIE Colloquium Summer Series

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July 29, 2014

On Tuesday, July 29th the UR SPIE student chapter will be continuing its Summer Colloquium series. Please bring your lunch and come listen to our next presentation! Snacks and beverages will be provided. 

Who: 
Jose Perez

What:
 Design and Characterization of L3 Photonic Crystal Nanocavities with Ultra-High Quality Factors
 
Abstract: Silicon-based photonic crystal nanocavities (PCNs) have potential applications in integrated quantum photonics [1, 2], because of their ability to strongly confine light in mode volumes approaching the diffraction limit and their CMOS-compatible fabrication process [3]. It was previously thought that PCN designs with a footprint small enough for ultra-dense integration, such as L3, H1 and H0 designs, could only achieve moderately high quality factors (Q), with both theoretical and experimental values never exceeding 300,000. Recently, an optimization procedure based on genetic algorithms has completely changed the scenario, showing a dramatic improvement of the Q-values in these PCNs [4]. A joint effort between our research group and a theory group at EPFL has resulted in the successful design and fabrication of a genetically improved L3 PCN with an ultra-high Q (~ 2 million), while maintaining a very small footprint and mode volume [5]. In this talk, I will describe the design process of these so-called super-L3 PCNs, as well as their characterization in the spectral domain using cross-polarization resonant scattering spectroscopy [6] and in the time domain using cavity ring down measurements [7].

When: 7/29/2014  11:30 am – 12:30 pm

Where: Sloan Auditorium (Goergen 101)
The SPIE Student Summer Colloquium Series is a weekly event to be held on Tuesdays from June to August. If you are a student willing to give a talk, please send an email to urspie@gmail.com with your talk title, a short abstract, and preferred talk date.
Do you want to know what your peers are doing in their research? Want to network with people from the same field? Would you like to benefit from scholarships and conference discounts? Well, then join SPIE now! Just go to spie.org to register to become a student member of the U of Rochester chapter or send an email to urspie@gmail.com if you have any questions.


 
References
 
[1]   J. O'Brien, A. Furusawa, and J. Vučković, "Photonic quantum technologies," Nature Photonics 3, 687-695 (2009).
[2]   J. Vuckovic, "Quantum optics and cavity QED with quantum dots in photonic crystals," arXiv:1402.2541 [quant-ph] (2014).
[3]   M. Notomi, "Manipulating light with strongly modulated photonic crystals," Reports on Progress in Physics 73, 096501 (2010).
[4]   M. Minkov and V. Savona, "Automated optimization of photonic crystal slab cavities," Scientific Reports (2014).
[5]   Y. Lai, S. Pirotta, G. Urbinati, D. Gerace, M. Minkov, V. Savona, A. Badolato, and M. Galli, "Genetically designed L3 photonic crystal nanocavities with quality factor exceeding one million," to be published, Applied Physics Letters (June 16, 2014).
[6]   M. Galli, S. L. Portalupi, M. Belotti, L. C. Andreani, L. O'Faolain, and T. F. Krauss, "Light scattering and Fano resonances in high-Q photonic crystal nanocavities," Applied Physics Letters 94, 071101 (2009).
[7]   T. Tanabe, M. Notomi, E. Kuramochi, A. Shinya, and H. Taniyama, "Trapping and delaying photons for one nanosecond in an ultrasmall high-Q photonic-crystal nanocavity," Nature Photonics 1, 49-52 (2007).
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Dept of Chemical Engineering PhD Defense

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July 30, 2014

Kevin Klubek
Professor Ching Tang, Chemical Engineering, Advisor
 
Investigation of Blue Phosphorescent Organic Light-Emitting Diode Instability
Phosphorescent emitters have played a critical role in the advance of organic light-emitting diode (OLED) technology. Among the phosphorescent emitters, the cyclometalated complexes with iridium (III) as the central atom are the most well developed and successfully commercialized. They are also among the most efficient. With chelating ligands specifically designed for color tuning, RGB (red, green and blue) emitters with nearly 100% (internal) quantum efficiency, defined as photons generated per injected electron, have been demonstrated. The operating lifetime of the phosphorescent OLED devices, however, remains an issue, particularly for the blue devices.
                    This thesis focuses on two phosphorescent blue dopants based on iridium; bis(4,6-difluorophenyl-pyridinato-N,C2) picolinate iridium (III) (FIrpic), and tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole] iridium (III) (Ir(iprpmi)3). FIrpic is perhaps the most well-known blue phosphorescent dopant that has demonstrated high quantum efficiency, but it has been found to produce short operational lifetimes. Ir(iprpmi)3 was chosen for this study because there were claims in patent literature that it provides excellent stability in OLED devices.
                    Using FIrpic as the blue dopant in the emitter layer, we have investigated the dependence of OLED performance, including device lifetime, on the compositions of the emitter layer (host-dopant) and the adjacent electron/hole transport layers. Regardless of the choice of the host materials in the emitter layer, or the materials in the transport layers, it is shown that the stability of OLED devices is poor (<12 hours) for devices using FIrpic as the blue phosphorescent dopant. Recombination that occurs on the host or transport materials is also found to be detrimental to device lifetime.
                    By tracking voltage and efficiency during operation for model devices with well known tris(8-hydroxyquinolinato) aluminum (Alq) as the emitter, it is shown that in addition to its instability in charge recombination processes, FIrpic is also unstable with respect to hole-transport processes. This indicates that the FIrpic radical cation itself is unstable. It is also found that the host 3,3'-bis(N-carbazolyl)biphenyl (mCBP) is unstable to electron-hole recombination processes.
                    The photophysical properties of Ir(iprpmi)3 were studied. This material has a low ionization potential of 4.8 eV, which is indicative of a material possessing strong electron donor characteristics. Electron donating materials are typically associated with hole injecting or hole transporting materials. By adjusting the concentration of Ir(iprpmi)3 within the host mCBP, we show that Ir(iprpmi)3 is capable of trapping (at low concentration) and transporting (at high concentration) holes. In this way, the location of the recombination zone (RZ) is modulated. At low concentrations the RZ is confined near the hole-transport layer whereas at high concentration the RZ is shifted towards the electron-transport layer. The external quantum efficiency, EQE, defined as photons exiting the device per injected electron, can reach >20% as long as the RZ is adjacent a charge transport material that has a higher triplet energy than Ir(iprpmi)3. Due to molecular structural differences, device lifetime using Ir(iprpmi)3 as the emitting dopant is significantly improved compared to FIrpic. However, the lifetime is also highly dependent on the choice of material for the host and charge transport layers.
 
Wednesday July 30, 2014:  Schlegel Hall 207:  10 AM
 
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Upcoming Events

 
  • UR SPIE Colloquium Summer Series
    July 29, 2014 — 11:30 am
  • Dept of Chemical Engineering PhD Defense
    July 30, 2014 — 10:00 am

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