Optics and Electronics Seminar

AP483 Optics & Electronics Seminar presents Ultrafast X-ray diffraction imaging with Free Electron Lasers

Topic: 
Ultrafast X-ray diffraction imaging with Free Electron Lasers
Abstract / Description: 

The advent of X-ray Free Electron Lasers (FELs) opens the door for unprecedented studies on non-crystallin nanoparticles with high spatial and temporal resolutions. In the recent past, ultrafast X-ray imaging studies with intense, femtosecond short FEL pulses have elucidated hidden processes in individual fragile specimens, which are inaccessible with conventional imaging techniques. Examples include airborne soot particle formation [1], metastable states in the synthesis of metal nanoparticles [2] and transient vortices in superfluid quantum systems [3] . Theoretically, ultrafast coherent diffraction X-ray imaging (CDI) could achieve atomic resolution in combination with sub-femtosecond temporal precision. Currently, the spatial resolution of ultrafast X-ray CDI is limited to several nanometers due to a combination of several factors such as X-ray photon flux, image imperfections and ultimately, sample damage [4] .

In this talk, I will present several experimental studies, which address these limitations and/or demonstrate the potential of ultrafast CDI. In the first part of the talk, I will report on a novel "in-flight" holographic method which overcomes the phase problem and paves the way for high-resolution X-ray imaging in presence of noise and image imperfections [5]. The second part will focus on potential applications of ultrafast X-ray CDI such as visualization of irreversible light-induced dynamics at the nanoscale with nanometer and sub-femtosecond resolutions [6]. In the third part, I will present world's first diffraction images of heavy atom nanoparticles recorded with isolated soft X-ray attosecond pulses. The study indicates that the combination of the optimal pulse length and X-ray energy can significantly deviate from linear models and control over transient resonances might be an efficient pathway for the improvement of spatial resolution [7] .

In summary, ultrafast CDI is a powerful method for studies of transient non-equilibrium dynamics at the nanoscale. The increasing number of X-ray FEL facilities, and the constant improvement in accelerator and X-ray focusing technology will broaden our capabilities to observe transient states of matter. This development will have a significant impact on research fields such as catalysis, nanophotonics, matter under extreme conditions, light-matter interactions and biological studies.

[1] Loh, N. D. et al. Fractal morphology, imaging and mass spectrometry of single aerosol particles in flight. Nature 486, 513–517 (2012).
[2] Barke, I. et al. The 3D-architecture of individual free silver nanoparticles captured by X-ray scattering. Nat. Commun. 6, (2015):6187.
[3] Gomez, L. F. et al. Shapes and vorticities of superfluid helium nanodroplets. Science 345, 906–909 (2014).
[4] Aquila, Andrew, et al., The linac coherent light source single particle imaging road map., Structur. Dyn. 2.4 (2015): 041701
[5] Gorkhover,T. et al., Femtosecond and nanometre visualization of structural dynamics in superheated nanoparticles. Nat. Phot. 10, (2016):93.
[6] Gorkhover,T.,et al., Femtosecond X-ray Fourier holography imaging of free-flying nanoparticles. Nat. Phot. 12.3, (2018): 150.
[7] Kuschel, S., et al, in prep.

Date and Time: 
Monday, January 14, 2019 - 4:15pm
Venue: 
Spilker 232

John G. Linvill Distinguished Seminar on Electronic Systems Technology

Topic: 
Internet of Things and Internet of Energy for Connecting at Any Time and Any Place
Abstract / Description: 

In this presentation, I would like to discuss with you how to establish a sustainable and smart society through the internet of energy for connecting at any time and any place. I suspect that you have heard the phrase, "Internet of Energy" less often. The meaning of this phrase is simple. Because of a ubiquitous energy transmission system, you do not need to worry about a shortage of electric power. One of the most important items for establishing a sustainable society is [...]


"Inaugural Linvill Distinguished Seminar on Electronic Systems Technology," EE News, July 2018

 

Date and Time: 
Monday, January 14, 2019 - 4:30pm
Venue: 
Hewlett 200

Optics & Electronics Seminar presents New designer materials: Sculpting electromagnetic fields on the atomic scale

Topic: 
New designer materials: Sculpting electromagnetic fields on the atomic scale
Abstract / Description: 

New optical nanomaterials hold the potential for breakthroughs in a wide range of areas from ultrafast optoelectronics such as modulators, light sources and hyperspectral detectors, to efficient upconversion for energy applications, bio-sensing and on-chip components for quantum information science. An exciting opportunity to realize such new nanomaterials lies in controlling the local electromagnetic environment on the atomic- and molecular-scale, (~1-10 nm) which enables extreme local field enhancements. We use creative nanofabrication techniques at the interface between chemistry and physics to realize this new regime, together with advanced, ultrafast optical techniques to probe the emerging phenomena. Here, I will provide an overview of our recent research including high-speed thermal photodetectors, ultrafast spontaneous emission and enhanced biosensors.

Date and Time: 
Monday, November 26, 2018 - 4:15pm
Venue: 
Spilker 232

Detecting Single Photons with Superconductors

Topic: 
Detecting Single Photons with Superconductors
Abstract / Description: 

From space communications to quantum communications to sensing dark matter, ultrasenstive, ultrafast photodetectors are required. But conventional detector technologies often fall short, exhibiting noise, slow response times, poor sensitivity, or a combination of these issues. In contrast, superconducting detectors based on nanowires provide a unique combination of high speed, excellent efficiency, and low noise. Their underlying physical operating mechanism also provides a rich parameter space for application of physics across the optical, condensed-matter, and microwave domains. For example, we have recently used an ultra-slow plasmonic microwave mode in the nanowires to demonstrate single-photon-sensitive imaging. This rich physical parameter space for engineering has has resulted in improved device performance and extended the impact of these devices even further.

Date and Time: 
Tuesday, November 27, 2018 - 4:15pm
Venue: 
Packard 101

OSA/SPIE Seminar presents Photovoltaic Restoration of Sight in Retinal Degeneration

Topic: 
Photovoltaic Restoration of Sight in Retinal Degeneration
Abstract / Description: 

Retinal degenerative diseases lead to blindness due to loss of the "image capturing" photoreceptors, while neurons in the "image-processing" inner retinal layers are relatively well preserved. Information can be reintroduced into the visual system using electrical stimulation of the surviving inner retinal neurons. Some electronic retinal prosthetic systems have been already approved for clinical use, but they provide low resolution and involve very difficult implantation procedures.

We developed a photovoltaic subretinal prosthesis which converts light into pulsed electric current, stimulating the nearby inner retinal neurons. Visual information is projected onto the retina from video goggles using pulsed nearinfrared (~880nm) light. This design avoids the use of bulky electronics and wiring, thereby greatly reducing the surgical complexity. Optical activation of the photovoltaic pixels allows scaling the implants to thousands of electrodes. In preclinical studies, we found that prosthetic vision with subretinal implants preserves many features of natural vision, including flicker fusion at high frequencies (>20 Hz), adaptation to static images, center-surround organization and non-linear summation of subunits in receptive fields, providing high spatial resolution. Results of the clinical trial with our implants (PRIMA, Pixium Vision) having 100µm pixels, as well as preclinical measurements with 75 and 55µm pixels, confirm that spatial resolution of prosthetic vision can reach the sampling density limit.

For a broad acceptance of this technology by patients who lost central vision due to age-related macular degeneration, visual acuity should exceed 20/100, which requires pixels smaller than 25µm. I will describe the fundamental limitations in electro-neural interfaces and 3-dimensional configurations which should enable such a high spatial resolution. Ease of implantation of these wireless arrays, combined with high resolution opens the door to highly functional restoration of sight.

Date and Time: 
Thursday, November 15, 2018 - 3:45pm
Venue: 
Shriram 262

AP483, Ginzton Lab, & AMO Seminar Series presents Impact of Structural Correlation and Monomer Heterogeneity in the Phase Behavior of Soft Materials and Chromosomal DNA

Topic: 
Impact of Structural Correlation and Monomer Heterogeneity in the Phase Behavior of Soft Materials and Chromosomal DNA
Abstract / Description: 

Polymer self-assembly plays a critical role in a range of soft-material applications and in the organization of chromosomal DNA in living cells. In many cases, the polymer chains are composed of incompatible monomers that are not regularly arranged along the chains. The resulting phase segregation exhibits considerable heterogeneity in the microstructures, and the size scale of these morphologies can be comparable to the statistical correlation that arises from the molecular rigidity of the polymer chains. To establish a predictive understanding of these effects, molecular models must retain sufficient detail to capture molecular elasticity and sequence heterogeneity. This talk highlights efforts to capture these effects using analytical theory and computational modeling. First, we demonstrate the impact of structural rigidity on the phase segregation of copolymer chain in the melt phase, resulting in non-universal phase phenomena due to the interplay of concentration fluctuations and structural correlation. We then demonstrate how these effects impact the phase behavior in statistical random copolymers and in heterogeneous copolymers based on chromosomal DNA properties. With these results, we demonstrate that the spatial segregation of DNA in living cells can be predicted using a heterogeneous copolymer model of microphase segregation.

Date and Time: 
Monday, November 5, 2018 - 4:15pm
Venue: 
Spilker 232

OSA/SPIE Seminar: Entanglement across disciplines

Topic: 
Entanglement across disciplines
Abstract / Description: 

As physicists or engineers we may be aware that philosophers and historians have long been interested in quantum theory and its potential ontological implications. Over the past few decades, diverse new branches of the humanities and social sciences have begun to grapple with aspects of quantum physics and to offer radical interpretive approaches. In this talk I'll briefly introduce some of these developments and then invite the audience to participate in an open discussion. The presentation will be non-technical in nature but I'll assume that everyone is familiar with the structure and application of quantum theory.

Date and Time: 
Wednesday, October 31, 2018 - 4:00pm
Venue: 
Spilker 232

AP483, Ginzton Lab, & AMO Seminar Series presents "Quantum Electrodynamics of Superconducting Circuits"

Topic: 
Quantum Electrodynamics of Superconducting Circuits
Abstract / Description: 

The demand for rapid and high-fidelity execution of initialization, gate and read-out operations casts tight constraints on the accuracy of quantum electrodynamic modeling of superconducting integrated circuits. Attaining the required accuracies requires reconsidering our basic approach to the quantization of the electromagnetic field in a light-confining medium and the notion of normal modes. I will discuss a computational framework based on the Heisenberg-Langevin approach to address these fundamental questions. This framework allows the accurate determination of the quantum dynamics of a superconducting qubit in an arbitrarily complex electromagnetic environment, free of divergences that have plagued earlier approaches. I will also discuss the effectiveness of this computational approach in meeting the demands of present-day quantum computing research.


Academic year 2018-2019, please join us at Spilker room 232 every Monday afternoon from 4 pm for the AP 483 & Ginzton Lab, and AMO Seminar Series.

Refreshments begin at 4 pm, seminar at 4:15 pm.

Date and Time: 
Monday, December 3, 2018 - 4:15pm
Venue: 
Spilker 232

AP483, Ginzton Lab, & AMO Seminar Series

Topic: 
When quantum-information scrambling met quasiprobabilities
Abstract / Description: 

We do physics partially out of a drive to understand essences. One topic whose essence merits understanding is the out-of-time-ordered correlator (OTOC). The OTOC reflects quantum manybody thermalization, chaos, and scrambling (the spread of quantum information through manybody entanglement). The OTOC, I will show, equals an average over a quasiprobability distribution. A quasiprobability resembles a probability but can become negative and nonreal. Such nonclassical values can signal nonclassical physics. The OTOC quasiprobability has several applications: Experimentally, the quasiprobability points to a scheme for measuring the OTOC (via weak measurements, which refrain from disturbing the measured system much). The quasiprobability also signals false positives in attempts to measure scrambling of open systems. Theoretically, the quasiprobability links the OTOC to uncertainty relations, to nonequilibrium statistical mechanics, and more strongly to chaos. As coarse-graining the quasiprobability yields the OTOC, the quasiprobability forms the OTOC's essence.

References
• NYH, Phys. Rev. A 95, 012120 (2017). https://journals.aps.org/pra/abstract/10.1103/PhysRevA.95.012120
• NYH, Swingle, and Dressel, Phys. Rev. A 97, 042105 (2018). https://journals.aps.org/pra/abstract/10.1103/PhysRevA.97.042105
• NYH, Bartolotta, and Pollack, arXiv:1806.04147 (2018). https://arxiv.org/abs/1806.04147
• Gonzàlez Alonso, NYH, and Dressel, arXiv:1806.09637 (2018). https://arxiv.org/abs/1806.09637
• Swingle and NYH, Phys. Rev. A 97, 062113 (2018). https://journals.aps.org/pra/abstract/10.1103/PhysRevA.97.062113
• Dressel, Gonzàlez Alonso, Waegell, and NYH, Phys. Rev. A 98, 012132 (2018). https://journals.aps.org/pra/abstract/10.1103/PhysRevA.98.012132


Academic year 2018-2019, please join us at Spilker room 232 every Monday afternoon from 4 pm for the AP 483 & Ginzton Lab, and AMO Seminar Series.

Refreshments begin at 4 pm, seminar at 4:15 pm.

Date and Time: 
Monday, November 12, 2018 - 4:15pm
Venue: 
Spilker 232

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