Seminar: "Femtosecond laser filamentation in air: the roles of optical nonlinearity and plasma generation" by Dr. Yu-hsin Chen 3.12.14/11:00am-12:00pm/ CREOL 102

Seminar: "Femtosecond laser filamentation in air: the roles of optical nonlinearity and plasma generation" by Dr. Yu-hsin Chen

Wednesday, March 12, 2014 11:00 AM to 12:00 PM
CREOL Room 102

Dr. Yu-hsin Chen

Abstract:

An intense femtosecond laser pulse propagating in a gas may collapse into one or multiple “filaments” when its peak power exceeds the critical power (5 – 10 GW in air) for nonlinear self-focusing. In atmosphere, the laser intensity is typically ~ 10¹³ W/cm² in the filament, leaving a weakly-ionized plasma channel which can extend meters in length with a diameter of < 100 μm. While it has been generally accepted that laser filamentation is the consequence of self-focusing-induced beam collapse stabilized by plasma generation and de-focusing, neither the field-induced nonlinearity nor the plasma generation had been directly measured. This uncertainty has given rise to recent controversy about whether plasma generation does indeed counteract the positive nonlinearity, as an alternate theory suggests that the stabilization mechanism is contributed by saturation of optical nonlinearity.

For a basic understanding of femtosecond filamentation and for applications, the focusing and defocusing mechanisms – nonlinear self-focusing and ionization – must be understood. By employing a single-shot, time-resolved technique based on spectral interferometry to study the constituents of air, it is found that the rotational responses in O₂ and N₂ are the dominant nonlinear effect in filamentary propagation when the laser pulse duration is longer than ~ 100 fs. Furthermore, we find that the instantaneous nonlinearity scales linearly up to the ionization threshold, suggesting that an ionization-free, negative stabilization of filamentation does not exist. This is confirmed by space-resolved plasma density measurements in meter-long filaments using optical interferometry with a grazing-incidence probe laser pulse.

Biography:

Dr. Yu-hsin Chen received the B.S. degree in electrical engineering and the M.S. in electro-optical engineering in 2000 and 2002, respectively, both from National Taiwan University. He obtained his Ph.D. degree in electrical engineering from University of Maryland, College Park in 2011. Then he worked as a postdoctoral researcher at Lawrence Livermore National Laboratory.

Dr. Chen’s research interests are in ultrafast lasers, nonlinear optics, high-intensity laser-plasma interactions, and laser acceleration of charged particles. He has won 2012 Marshall N. Rosenbluth Outstanding Doctoral Thesis Award in plasma physics, for his work on femtosecond laser filamentation in atmosphere.

For additional information:

Dr. Martin C. Richardson

Pegasus Professor and University Trustee Chair, Northrop Grumman Prof of X-ray Photonics; Prof of Optics; Director Townes Laser Institute

407-823-6819

mcr @ creol . ucf . edu

Seminar: "Current status of clinical breath analysis including laser-based analysis" by Terence H. Risby

Seminar: "Current status of clinical breath analysis including laser-based analysis" by Terence H. Risby

Friday, February 28, 2014 12:00 PM to 1:00 PM
CREOL Room 102

Terence H. Risby

PhD, Department of Environmental Health Sciences, Johns Hopkins University

Abstract:

Although clinical breath analysis is currently in its infancy it offers unique capabilities to the field of medicine.  Breath can be collected multiple times non-invasively from humans without posing any risk to the subject or the person collecting the sample.  Breath can be collected easily in the field and the samples returned to the laboratory for analysis.  Real-time monitors are currently being developed and these devices could be well suited for field and epidemiological studies, particularly for studies in developing countries where collecting blood and urine samples are difficult without refrigeration.  If inexpensive portable real-time monitors can be developed for point-of-care testing then chronically sick patients could monitor their progress in their home and thereby minimizing their exposure to infections during routine visits to clinics.  Breath analysis can be used to detect disease, monitor disease progression, or monitor therapy.  Breath analysis can be used for phase 1 and phase 2 clinical trials to monitor new drug therapy or to detect potential adverse effects.  Since breath analysis is non-invasive and can be performed easily, it allows larger numbers of study subjects to be studied.  Using larger numbers of study subjects, unusual adverse effects are more likely to be identified.  This presentation will discuss the current status of “clinical breath analysis”.

For additional information:

Konstantin Vodopyanov

407-823-6818

vodopyanov @ creol . ucf . edu

TODAY! Seminar: "Developing photoacoustic imaging technologies and optical coherence tomography for clinical applications and the “BRAIN” initiative" by Bin Rao 2.28.14/10:30am-11:30am/ CREOL 102

Seminar: "Developing photoacoustic imaging technologies and optical coherence tomography for clinical applications and the “BRAIN” initiative" by Bin Rao

Friday, February 28, 2014 10:30 AM to 11:30 AM
CREOL Room 102

Abstract:

Photoacoustic imaging (PAI) technologies are hybrid optical imaging technologies that acoustically detect optical absorption contrasts via the photoacoustic effect. Major PAI technologies include photoacoustic computed tomography (PACT), acoustic-resolution photoacoustic microscopy (AR-PAM) and optical-resolution photoacoustic microscopy (OR-PAM). The major strengths of PAI are the deep imaging capability of PACT and AR-PAM, and the functional, high resolution, optical absorption contrast images of reflection mode OR-PAM. Optical coherence tomography (OCT) forms three-dimensional tissue structure images by probing weak back-scattered photons with coherent gating and coherent amplification. OCT offers high sensitivity, and provides functional, high resolution optical scattering contrast images. Major PAI and OCT imaging systems and applications that I developed at the Beckman Laser Institute & Medical Clinic of University of California, Irvine (BLIMC-UCI), and at Washington University in St. Louis are reviewed. Highlights are the spectral Doppler imaging and quantification of pulsatile retinal blood flow of human patients at BLIMC-UCI, in vivo recording of epilepsy seizure in a small animal model by a dual-modality PAM and OCT imaging system, and the development of miniature OR-PAM imaging probes for imaging port-wine stain (PWS) in children. Finally, I will discuss developing PAI and OCT for both clinical applications and the “BRAIN” initiative(a bold new research effort to revolutionize our understanding of the human mind and uncover new ways to treat, prevent, and cure brain disorders like Alzheimer’s, schizophrenia, autism, epilepsy, and traumatic brain injury).

Biography:

Bin Rao received his Ph.D. on biomedical optics from Beckman Laser Institute & Medical clinic, University of California, Irvine (BLIMC-UCI) in 2008. His post-doctor trainings at Washington University in Saint Louis include photoacoustic microscopy, confocal, and two-photon microscopy. He has built two clinical imaging systems, including the spectral Doppler optical coherence tomography instrument for quantifying pulsatile retinal blood flow, and the photoacoustic microscopy system for imaging port-wine stain in children. Both clinical imaging systems are being used by clinicians in clinical studies at BLIMC-UCI. He was awarded the NIH Pathway to Independence Award in 2012.

For additional information:

Dr. Bahaa E. A. Saleh

Dean & Director, Professor of Optics

407-882-3326

besaleh @ creol . ucf . edu

Physics Colloquium - Friday, February 28, 4:30 pm, PSB 161

Dr. Ileana Rau - IBM Almaden Research Center

Toward Single Atom Magnets

:

Magnetic anisotropy is a fundamental property of magnetic materials that governs the stability and directionality of their magnetization. The ability to control the magnetic anisotropy of nanoscale systems will open novel avenues for spintronics, magnetic memory devices, and quantum computation. At the atomic level, magnetic anisotropy originates from the spin-orbit coupling that connects the spin moment of a magnetic atom to the spatial symmetry of its ligand or crystal field environment. In the case of 3d transition metal atoms, the same crystal field that is necessary for the anisotropy usually quenches the orbital moment and reduces the total magnetic moment of the atom to its spin component. As a result, single molecule magnets and magnetic tunnel junctions show an anisotropy energy per atom that is typically one to two orders of magnitude smaller than the maximal value allowed by the spin-orbit coupling. We have overcome this limitation by carefully designing the coordination geometry of magnetic atoms on a surface to preserve the orbital moment while inducing uniaxial anisotropy. I will present scanning tunneling spectroscopy and x-ray absorption spectroscopy measurements that show that single Cobalt atoms deposited on a thin MgO layer retain most of their free-atom orbital moment L=3. Because Cobalt adsorbs on top of the Oxygen atom, the resulting crystal field is effectively cylindrical and leads to a strikingly large magnetic anisotropy energy, at the theoretical limit. Spin-polarized tunneling measurements reveal a stable magnetic groundstate with a large total moment of ~5.5mB and a long-lived excited state of opposite magnetic moment with a relaxation time of 0.2 ms. These results offer a strategy, based on symmetry arguments and careful tailoring of the interaction with the environment for the rational design of nanoscopic permanent magnets and single atom magnets.

Seminar: "Developing photoacoustic imaging technologies and optical coherence tomography for clinical applications and the “BRAIN” initiative" by Bin Rao 2.28.14/10:30am-11:30am/CREOL 102

Seminar: "Developing photoacoustic imaging technologies and optical coherence tomography for clinical applications and the “BRAIN” initiative" by Bin Rao

Friday, February 28, 2014 10:30 AM to 11:30 AM
CREOL Room 102

Abstract:

Photoacoustic imaging (PAI) technologies are hybrid optical imaging technologies that acoustically detect optical absorption contrasts via the photoacoustic effect. Major PAI technologies include photoacoustic computed tomography (PACT), acoustic-resolution photoacoustic microscopy (AR-PAM) and optical-resolution photoacoustic microscopy (OR-PAM). The major strengths of PAI are the deep imaging capability of PACT and AR-PAM, and the functional, high resolution, optical absorption contrast images of reflection mode OR-PAM. Optical coherence tomography (OCT) forms three-dimensional tissue structure images by probing weak back-scattered photons with coherent gating and coherent amplification. OCT offers high sensitivity, and provides functional, high resolution optical scattering contrast images. Major PAI and OCT imaging systems and applications that I developed at the Beckman Laser Institute & Medical Clinic of University of California, Irvine (BLIMC-UCI), and at Washington University in St. Louis are reviewed. Highlights are the spectral Doppler imaging and quantification of pulsatile retinal blood flow of human patients at BLIMC-UCI, in vivo recording of epilepsy seizure in a small animal model by a dual-modality PAM and OCT imaging system, and the development of miniature OR-PAM imaging probes for imaging port-wine stain (PWS) in children. Finally, I will discuss developing PAI and OCT for both clinical applications and the “BRAIN” initiative(a bold new research effort to revolutionize our understanding of the human mind and uncover new ways to treat, prevent, and cure brain disorders like Alzheimer’s, schizophrenia, autism, epilepsy, and traumatic brain injury).

Biography:

Bin Rao received his Ph.D. on biomedical optics from Beckman Laser Institute & Medical clinic, University of California, Irvine (BLIMC-UCI) in 2008. His post-doctor trainings at Washington University in Saint Louis include photoacoustic microscopy, confocal, and two-photon microscopy. He has built two clinical imaging systems, including the spectral Doppler optical coherence tomography instrument for quantifying pulsatile retinal blood flow, and the photoacoustic microscopy system for imaging port-wine stain in children. Both clinical imaging systems are being used by clinicians in clinical studies at BLIMC-UCI. He was awarded the NIH Pathway to Independence Award in 2012.

For additional information:

Dr. Bahaa E. A. Saleh

Dean & Director, Professor of Optics

407-882-3326

besaleh AT creol . ucf . edu

Seminar: "Label-free cellular imaging and tissue turbidity suppression" by Dr. Zahid Yaqoob 2.24.14/11:00am-12:00pm/ CREOL Room 102

Seminar: "Label-free cellular imaging and tissue turbidity suppression" by Dr. Zahid Yaqoob

Monday, February 24, 2014 11:00 AM to 12:00 PM
CREOL Room 102

Dr. Zahid Yaqoob

Laser Biomedical Research Center

Massachusetts Institute of Technology

Abstract:

Optical imaging and spectroscopy of biological cells and tissue can provide tremendous information that may be utilized for both diagnostic and therapeutic applications. A major challenge in optical imaging, however, is to elicit relevant information in a label-free fashion. While cells are generally transparent that leads to diminished image contrast, biological tissue is highly scattering that limits the working depth range of current optical imaging and spectroscopy modalities. Remarkably, quantitative analysis of amplitude and phase characteristics of the transmitted or backscattered light can lead to label-free structural and functional imaging in live cells. I will discuss the development of two- and three-dimensional quantitative phase microscopy and its applications including dry mass (non-aqueous content) measurements to study cell growth and division. Accurate optical field-based measurements can also be utilized to quantify and control multiple light scattering in turbid media. This topic has attracted significant interest in recent years, leading to different approaches for overcoming tissue turbidity. I will present active wavefront control via optical phase conjugation and demonstrate its efficacy in permitting high-fidelity wide-field imaging through turbid media.

Biography:

Dr. Yaqoob obtained his MS and PhD in Optics from The College of Optics and Photonics/CREOL, University of Central Florida. He received his postdoctoral training in biomedical optics at CalTech and MIT. He is currently a Research Scientist at the MIT Laser Biomedical Research Center, where his research is focused on developing innovative photonic solutions for complex problems in biological research and medical diagnosis. He is particularly interested in applying these tools to understand highly regulated physiological and pathological processes at single cell level. His research also focuses on developing strategies to harness multiple light scattering in biological tissue with the aim to improve the working depth range of current optical imaging and spectroscopy tools. He has published in more than 85 peer-reviewed journals and conference proceedings.

For additional information:

Dr. M. G. "Jim" Moharam                                                                     

Professor of Optics

407-823-6833

moharam AT creol . ucf . edu

TODAY! Distinguished Seminar Series: "Diffractive optics for short wavelengths and short pulses" by Jürgen Jahns 2.17.14/11:00am-12:00pm/ CREOL 102

Distinguished Seminar Series: "Diffractive optics for short wavelengths and short pulses" by Jürgen Jahns

Monday, February 17, 2014 11:00 AM to 12:00 PM
CREOL Room 102

 Jürgen Jahns

FernUniversitat in Hagen, Germany

Abstract:

Over the past 20 years, diffractive optics has developed from an area of active research to a mature field with numerous commerical applications. And yet, there exists still a potential for novel applications and thus interesting research topics. Here, I will discuss two topics: the first is imaging at EUV and X-ray wavelengths using diffractive lenses, the second is the spatio-temporal filtering of ultrashort pulses using diffractive optics.

Focusing and imaging of EUV and x-ray radiation (i.e., at wavelengths from approximately 0.1 - 100 nm) has many applications, for example, in astronomy and the life sciences. However, at these wavelengths, the use of conventional refractive lenses is not practical, since all materials are strongly absorbing and the values of the refractive index are very close to one. As an alternative to using refraction, a one may consider a diffractive implementation. Special diffractive lenses, such as the “photon sieve” and “azimuthally modulated Fresnel zone plate” have been demonstrated in recent years. Here, the concepts behind these elements will be described and a diffraction-theoretical analysis will be presented.

 The second topic to be addressed is the use of microoptical elements for the shaping and filtering of ultrashort optical pulses. Shaping in the spatial domain includes, for example, the generation of vortex beams. A diffractive implementation of a vortex beam is achieved by a so-called spiral axicon. Using diffraction, however, leads to strong chromatic dispersion which is a problem for ultrashort pulses. Here, a refractive-diffractive dispersion compensation is presented.

 Finally, we show the fabrication of a highly precise micro-retroreflector array by the LIGA technology and discuss the possibility of using it as a time-domain filter for femtosecond pulses.

Biography:

Jurgen Jahns got his diploma and doctorate in physics from the University of Erlangen-Nuremberg, Germany, in 1978 and 1982, respectively. He worked at Siemens, Munich, Germany, and at AT&T Bell Laboratories, Holmdel, New Jersey, before becoming full professor and chair of optical information technology at the FernUniversitat in Hagen, Germany, in 1994. He has co-authored more than 95 journal articles and several books on microoptics and photonics. Jahns is a Fellow of OSA and SPIE and a member of DGaO (German Society of Applied Optics), EOS, and IEEE.

For additional information:

Dr. Bahaa E. A. Saleh

Dean & Director, Professor of Optics

407-882-3326

besaleh AT creol . ucf . edu

SI seminar Cancelled

Dr. Alberto Fairen’s talk on “Water on Early Mars” has been cancelled. Was scheduled February 20 from 3:30 – 4:30 in room 209.

Carol Cox

FSI Senior Clerk

407-823-6187

FSI Seminar 2/5

Florida Space Institute Seminar Announcement

Speaker: Tracy Becker and Zoe Landsman

Affiliation: UCF Physics

Day and Date: Wednesday, February 5, 2014

Time: 11:00 – 12:00

Location: Research Park

12354 Research Parkway

Partnership 1 Bldg. Suite 209

Orlando, FL 32826

Florida Space Grant Consortium (FSGC) Fellowship Prize Talk:

Doctoral Candidate

UCF- Planetary Sciences Group

Tracy’s Abstract:

The particles that constitute Saturn’s rings range from micron-sized dust to small boulders. The presence of small particles is a signature of more energetic collisions between ring particles, while the absence of dust indicates that the particles are aggregating into larger clumps. Characterizing the size distribution of particles throughout the rings therefore provides insight into the dynamical environment of the ring particles. We examine stellar and solar occultation data from the Cassini spacecraft to measure detections of forward-scattered light by the smallest particles. We present results from computer models that reproduce the signature of the forward-scattered light and thereby constrain the size distribution of particles throughout Saturn’s rings.

Presenter Zoe Landsman

Graduate Research Fellow

UCF- Planetary Sciences Group

Zoe’s Abstract:

The M-type asteroids have traditionally been interpreted as the disrupted iron cores of differentiated bodies by spectral analogy with the nickel-iron meteorites. More detailed studies have revealed the presence of hydrated minerals on M-type asteroids (e.g., Jones et al. 1990, Rivkin et al. 1995, 2000, Fornasier et al. 2010, Ockert-Bell et al. 2010), challenging the notion that these bodies are highly thermally evolved. We seek to characterize the 2 - 4 micron spectra of M-type asteroids, as this wavelength range is diagnostic of hydrated minerals (Rivkin et al. 2002, Takir and Emery 2012). With this work, we hope to shed new light on the origin of hydration on M-type asteroids and its context within the mineralogy and thermal evolution of these bodies.

For further information please click below:

http://fsi.ucf.edu/seminars/ 

                         

 

  

Seminar-"Current status of clinical breath analysis"-Terence H. Risby/ 2.28.14/ 12:00pm-1:00pm/ CREOL 102

Seminar-"Current status of clinical breath analysis"-Terence H. Risby/ 2.28.14/ 12:00pm-1:00pm/ CREOL 102

Prof. Terence H. Risby, Department of Environmental Health Sciences,
Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD
 

Abstract:
Although clinical breath analysis is currently in its infancy it offers unique capabilities to the field of medicine.  Breath can be collected multiple times non-invasively from humans without posing any risk to the subject or the person collecting the sample.  Breath can be collected easily in the field and the samples returned to the laboratory for analysis.  Real-time monitors are currently being developed and these devices could be well suited for field and epidemiological studies, particularly for studies in developing countries where collecting blood and urine samples are difficult without refrigeration.  If inexpensive portable real-time monitors can be developed for point-of-care testing then chronically sick patients could monitor their progress in their home and thereby minimizing their exposure to infections during routine visits to clinics.  Breath analysis can be used to detect disease, monitor disease progression, or monitor therapy.  Breath analysis can be used for phase 1 and phase 2 clinical trials to monitor new drug therapy or to detect potential adverse effects.  Since breath analysis is non-invasive and can be performed easily, it allows larger numbers of study subjects to be studied.  Using larger numbers of study subjects, unusual adverse effects are more likely to be identified.  This presentation will discuss the current status of “clinical breath analysis”, including the analysis that uses methods of laser spectroscopy. 

 

Biography:

One of the areas of Dr. Risby's research has focused on the development of novel, highly sensitive analytical chemical approaches for the assessment of biomarkers of tissue injury and disease in the breath. His laboratory has developed breath markers of cholesterol biosynthesis, liver dysfunction, nutritional status, and the effects of exposure to environmental toxicants. Over decades of investigation in volatile biomarkers, he has refined methods of breath collection and analysis to make breath sampling reproducible, accurate, and rapid.  He has trained more than thirty graduate students, residents, and post doctoral fellows. 

For additional information:

Dr. Konstantin L. Vodopyanov

Professor of Optics

407-823-6818

vodopyanov @ creol. ucf . edu