Optics and Electronics Seminar

OSA/SPIE, SPRC and Ginzton Lab present "Recent Advances in Submarine Fiber Optical Systems"

Topic: 
Recent Advances in Submarine Fiber Optical Systems
Abstract / Description: 

Undersea fiber optical systems have shown tremendous advances over the past one or two decades. Capacities have increased by 20x while the cost per bit of submarine transmission has decreased by 250 times. These advances have been primarily a result of coherent transmission and I will highlight all of the main points regarding these advances. This has led to the recent deployment of 16-QAM transmission on a trans-Atlantic link! Future directions in submarine fiber optic transmission systems, such as SDM, will also be discussed.

Date and Time: 
Thursday, May 23, 2019 - 4:15pm
Venue: 
Spilker 232

OSA/SPIE, SPRC and Ginzton Lab present "Hot Topics in Optics and Photonics"

Topic: 
Hot Topics in Optics and Photonics
Abstract / Description: 

Optics and photonics is a diverse field, spanning dynamic commercial successes to slowly-moving niche markets to speculative research and fundamental science. But most people only work in small spaces of the field at a given time, whether they are working in industry or academia. It can be difficult to visualize the entire field and understand it. How do you forecast where the technology is going? What is the Next Big Thing? How do you know what is a hot topic and what is a buzzword? This talk will provide ways of looking at current hot topics in photonics, in both the research funding and commercial markets. It will also give some perspectives on selected topics and where they are going. The talk will give "market perspectives," which is to say that it's about the overall environment and near- to mid-term future, rather than recent scientific results.

Date and Time: 
Thursday, May 16, 2019 - 4:15pm
Venue: 
Spilker 232

OSA/SPIE present "Measuring Everything You've Always Wanted to Know About a Light Pulse"

Topic: 
Measuring Everything You've Always Wanted to Know About a Light Pulse
Abstract / Description: 

The vast majority of the greatest scientific discoveries of all time have resulted directly from more powerful techniques for measuring light. Indeed, our most important source of information about our universe is light, and our ability to extract information from it is limited only by our ability to measure it.


Interestingly, most of the light in our universe remains immeasurable, involving long pulses of relatively broadband light, necessarily involving ultrafast and extremely complex temporal variations in their intensity and phase. As a result, it is important to develop techniques for measuring, ever more completely, light with ever more complex submicron detail in space and ever more complex ultrafast variations in time. The problem is severely complicated by the fact that the timescales involved correspond to the shortest events ever created, and measuring an event in time seems to require a shorter one, which, by definition, doesn't exist!
Nevertheless, we have developed simple, elegant techniques for completely measuring such light, using the light to measure itself and yielding a light pulse's intensity and phase vs. time and space. One technique involves making an optical spectrogram of the pulse using a nonlinear optical medium and whose mathematics is equivalent to the two-dimensional phase-retrieval problem—a problem that's solvable only because the Fundamental Theorem of Algebra fails for polynomials of two variables. In addition, we have recently developed simple methods for measuring the complete spatio-temporal electric field [E(x,y,z,t)] of an arbitrary, potentially complex light pulse without the need to average over multiple pulses.

Date and Time: 
Friday, May 10, 2019 - 4:15pm
Venue: 
Packard 101

OSA/SPIE, SPRC and Ginzton Lab present "Effective medium approach towards topological photonics"

Topic: 
Effective medium approach towards topological photonics
Abstract / Description: 

Metamaterials have attracted tremendous attention due to their exotic optical properties and functionalities that are not attainable from naturally occurring materials. In particular, metamaterials can be designed to introduce strong spin-orbit coupling for light and consequently nontrivial topological properties. In this talk, I will start with a brief introduction to the concepts of Berry curvature, Chern number and topological photonics. I will show that combination of chirality and hyperbolicity – an extreme form of anisotropy, can result in nontrivial topological orders in metamaterials and consequently topologically protected photonic surface states that are immune from scattering by defects and sharp edges. The Weyl points in such systems result from the crossing between the bulk longitudinal plasmon mode and the transverse circularly polarized propagating modes. The photonic 'Fermi arcs' were directly observed in the microwave regime, which showed Riemann-surface like helicoid configuration in the energy-momentum space. I will further show that by designing the Weyl metamaterials with inhomogeneous unit cells, artificial magnetic field can be introduced which leads to the first observation of chiral zero Landau mode in photonic systems.

Date and Time: 
Monday, May 6, 2019 - 4:30pm
Venue: 
Y2E2 299

AP483 & AMO Seminar welcomes Tomas Cizmar, "Harnessing Multimode Propagation for Deep-tissue Imaging"

Topic: 
Harnessing Multimode Propagation for Deep-tissue Imaging
Abstract / Description: 

The turbid nature of refractive index distribution within living tissues introduces severe aberrations to light propagation thereby severely compromising image reconstruction using currently available non-invasive techniques. Numerous approaches of endoscopy, based mainly on fibre bundles or GRIN-lenses, allow imaging within extended depths of turbid tissues, however their footprint causes profound mechanical damage to all overlying regions and their imaging performance is limited.

Progress in the domain of complex photonics enabled a new generation of minimally invasive, high-resolution endoscopes by substitution of the Fourier-based image relays with a holographic control of light propagating through apparently randomizing multimode optical waveguides. This form of endo-microscopy became recently a very attractive way to provide minimally invasive insight into hard-to-access locations within living objects.

Professor Čižmár will review our fundamental and technological progression in this domain and introduce several applications of this concept in bio-medically relevant environments.


 

 

AP 483 & AMO Seminar Series
Time:
4:15 pm, every Monday (Refreshments begin at 4 pm)

Location:
Spilker Building Room 232

Date and Time: 
Monday, May 20, 2019 - 4:15pm
Venue: 
Spilker 232

AP483 & AMO Seminar presents "Computational Microscopy in Multiple-Scattering Samples"

Topic: 
Computational Microscopy in Multiple-Scattering Samples
Abstract / Description: 

Computational imaging involves the joint design of imaging system hardware and software, optimizing across the entire pipeline from acquisition to reconstruction. Computers can replace bulky and expensive optics by solving computational inverse problems. This talk will describe new microscopes that use computational imaging to enable 3D fluorescence and phase imaging in samples that incur multiple scattering. Our reconstruction algorithms are based on large-scale nonlinear non-convex optimization. Applications span optical bioimaging, X-ray and electron microscopy.


 

AP 483 & AMO Seminar Series

Time:
4:15 pm, every Monday (Refreshments begin at 4 pm)

Location:
Spilker Building Room 232

Date and Time: 
Monday, May 13, 2019 - 4:15pm
Venue: 
Spilker 232

#StanfordToo: A Conversation about Sexual Harassment in Our Academic Spaces

Topic: 
#StanfordToo: A Conversation about Sexual Harassment in Our Academic Spaces
Abstract / Description: 

Individuals of all genders invited to be a part of:
#StanfordToo: A Conversation about Sexual Harassment in Our Academic Spaces, where we will feature real stories of harassment at Stanford academic STEM in a conversation with Provost Drell, Dean Minor (SoM), and Dean Graham (SE3). We will have plenty of time for audience discussion on how we can take concrete action to dismantle this culture and actively work towards a more inclusive Stanford for everyone. While our emphasis is on STEM fields, we welcome and encourage participation from students, postdocs, staff, and faculty of all academic disciplines and backgrounds.

Date and Time: 
Friday, April 19, 2019 - 3:30pm
Venue: 
STLC 111

OSA/SPIE, SPRC and Ginzton Lab present "Frequency comb-based nonlinear spectroscopy"

Topic: 
Frequency comb-based nonlinear spectroscopy
Abstract / Description: 

Rapid and precise measurements are and always have been of interest in science and technology partly because of their numerous practical applications. Since their development, frequency comb-based methods have revolutionized optical measurements. They simultaneously provide high resolution, high sensitivity, and rapid acquisition times. These methods are being developed for use in many fields, from atomic and molecular spectroscopy, to precision metrology, to spectral LIDAR and even atmospheric monitoring. However they cannot address the issues of inhomogeneously broadened transitions or sample heterogeneity. This is especially important for remote chemical sensing applications.

In this talk I will discuss a novel optical method, that I recently developed, which overcomes these limitations. I will demonstrate its capabilities for probing extremely weak fundamental processes as well as its applications for rapid and high resolution chemical sensing.

 

References:

B. Lomsadze, B. Smith and S. T. Cundiff. "Tri-comb spectroscopy". Nature Photonics 12, 676, 2018.
B. Lomsadze and S. T. Cundiff. "Frequency-comb based double-quantum two-dimensional spectrum identifies collective hyperfine resonances in atomic vapor induced by dipole-dipole interactions." Physical Review Letters 120, 233401, 2018.
B. Lomsadze and S. T. Cundiff. "Frequency combs enable rapid and high-resolution multidimensional coherent spectroscopy". Science 357, 1389, 2017
B. Lomsadze and S. T. Cundiff. "Frequency comb-based four-wave-mixing spectroscopy". Optics letters 42, 2346, 2017

Date and Time: 
Wednesday, June 12, 2019 - 4:15pm
Venue: 
Allen 101X

RESCHEDULED: OSA/SPIE, SPRC and Ginzton Lab present "Frequency comb-based nonlinear spectroscopy"

Topic: 
RESCHEDULED: Frequency comb-based nonlinear spectroscopy: Bridging the gap between fundamental science and cutting-edge technology
Abstract / Description: 

RESCHEDULED for June 12

Rapid and precise measurements are and always have been of interest in science and technology partly because of their numerous practical applications. Since their development, frequency comb-based methods have revolutionized optical measurements. They simultaneously provide high resolution, high sensitivity, and rapid acquisition times. These methods are being developed for use in many fields, from atomic and molecular spectroscopy, to precision metrology, to spectral LIDAR and even atmospheric monitoring. However they cannot address the issues of inhomogeneously broadened transitions or sample heterogeneity. This is especially important for remote chemical sensing applications.

In this talk I will discuss a novel optical method, that I recently developed, which overcomes these limitations. I will demonstrate its capabilities for probing extremely weak fundamental processes as well as its applications for rapid and high resolution chemical sensing.

 

References:

B. Lomsadze, B. Smith and S. T. Cundiff. "Tri-comb spectroscopy". Nature Photonics 12, 676, 2018.
B. Lomsadze and S. T. Cundiff. "Frequency-comb based double-quantum two-dimensional spectrum identifies collective hyperfine resonances in atomic vapor induced by dipole-dipole interactions." Physical Review Letters 120, 233401, 2018.
B. Lomsadze and S. T. Cundiff. "Frequency combs enable rapid and high-resolution multidimensional coherent spectroscopy". Science 357, 1389, 2017
B. Lomsadze and S. T. Cundiff. "Frequency comb-based four-wave-mixing spectroscopy". Optics letters 42, 2346, 2017

Date and Time: 
Wednesday, March 20, 2019 - 4:15pm
Venue: 
Allen 101X

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

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