Home Graduate Center CUNYfirst Bb MyQC Queens College

Colloquia

Sign up to receive notifications about colloquia:
“ That is the essence of science: ask an impertinent question, and you are on the way to a pertinent answer. ”
- Jacob Bronowski
iCal feed feed Help icon
iCalendar (*.ics extension) is a popular file format used to distribute calendar information between different applications over the internet.

Once you click the iCal feed link with the right button, copy the link URL and paste it into any calendar app that takes iCal feeds (Google Calendar, Outlook, etc).

Left click on a single event downloads the *.ics file with selected event, but it will not allow calendar apps to update automatically their calendar with other or upcoming events.

How to use feed with:
Google Calendar
Microsoft Outlook
Mozilla Thunderbird
Physics Conference Room, SB B326
Coffee starts at 12:00 PM and talk starts at 12:15 PM
8
Jan '18
Mitsuteru Inoue  -  Monday, January 8, 2018
PDFDownload PDF locationPhysics Conference Room, SB B326 coffee time2:45 pm talk time3:00 pm
ABSTRACT:
The introduction of artificial magnetic structures into magnetic materials can induce novel electromagnetic and spin-wave behavior. Nano- and submicrometer-scale artificial magnetic lattices (AMLs) can control optical (electromagnetic) waves in magnetophotonic crystals [1], volumetric magnetic holograms [2], and labyrinthian magnetic domain structures [3], and can affect spin waves in magnonic crystals [4].
     In this talk, the fundamental properties of such AMLs, mainly in magnetic garnet films and alloy thin films, are discussed, followed by demonstrations of their applications in optical and spin-wave micro-devices driven by magnetic phase interference: volumetric magneto-optic (MO) hologram memories [2] and three-dimensional MO holographic displays [5] with magnetophotonic crystals; high-speed MO Q-switch micro-chip lasers with iron-garnet films with labyrinthian magnetic domain structures [3]; and highly sensitive magnetic sensors and spinwave logic circuits with magnonic crystals [6].
     Prospective future spin-wave devices with AMLs will be discussed in the context of the new paradigm of magnonics (electron non-transport electronics), where spin waves play an important role as the information carrier.
 
[1] T. Goto et al., “Magnetophotonic crystal comprising electro-optical layer for controlling helicity of light,” J. Appl. Phys., 111, 07A913, 2012.
[2] Y. Nakamura et al., “Error-free reconstruction of magnetic hologram via improvement of recording conditions in collinear optical system,” Optics Exp., 25, 15349-15357, 2017.
[3] R. Morimoto et al., “Magnetic domains driving a Q-switched laser,” Sci. Rep., 6, 38679, 2016.
[4] N. Kanazawa et al., “Metal thickness dependence on spin wave propagation in magnonic .crystal using yttrium iron garnet,” J. Appl. Phys., 117, 17E510, 2015.
[5] K. Nakamura et al., “Improvement of diffraction efficiency of three-dimensional magnetooptic spatial light modulator with magnetophotonic crystal,” Appl. Phys. Lett., 108, 02240, 2016.
[6] N. Kanazawa et al., “Demonstration of a robust magnonic spin wave interferometer,” Sci. Rep., 6. 30268, 2016.
 
NOTES: Professor Inoue is IEEE Magnetics Society Distinguished Lecturer for 2018
29
Jan '18
Mircea Trif  -  Monday, January 29, 2018
ABSTRACT: The field of cavity quantum electrodynamics (cQED) with quantum conductors has become an extremely active field of research. The milestone year was 2004, when superconducting qubits have been integrated within a microwave cavity in order to reach, for the very first time in the condensed matter context, the strong coupling regime between photons and matter [1,2]. Since then, many other systems have been successfully coupled to microwave cavities, such as quantum wires [3], carbon nanotubes [4], quantum dots [5], etc. Such hybrid systems offer platforms for new kinds of physics, as one can engineer and manipulate the electromagnetic environment at will. The versatility of the cQED method relies on the fact that it allows to 1) monitor in a noninvasive fashion the electronic states in quantum conductors, both in equilibrium and non-equilibrium situations, 2) to affect and manipulate the electronic transport, 3) to establish long-range correlations between remote quantum conductors and, finally, 4) it opens the pathway to create non-classical states of light by means of electronic transport.

In this talk, I will discuss some of these aspects for various types of quantum conductors out of equilibrium. I will focus on tunnel junctions [5], magnetic tunnel junctions [6], quantum dots [5] and Josephson junctions [7,8], respectively. I will show that one can reveal properties that are invisible in electronic transport (via the conductance), in particular in out-of-equilibrium situations pertaining to a large voltage bias applied over the quantum conductor [8]. For the case of voltage biased Josephson junction, I will show that the emitted radiation is non-classical in the sense that the photonic correlators violate some Cauchy-Schwarz inequalities [9]. I will confront the theory with some recent experimental studies where such violations have been measured [10].

References:
[1] A. Wallraf, D. I. Schuster, A. Blais et al., Nature 431, 162 (2004).
[2] A. Blais et al., Phys. Rev. A 69, 062320 (2004).
[3] K. D. Petersson et al., Nature 490, 380 (2012). [4] J. Viennot et al., Science 349, 6246 (2015).
[4] T. Frey et al., Phys. Rev. Lett. 108, 046807 (2010).
[5] Olesia Dmytruk, Mircea Trif, Christophe Mora, and Pascal Simon, Phys. Rev. B 93, 075425 (2016).
[6] Mircea Trif and Pascal Simon, Phys. Rev. B 90, 174431 (2014).
[7] Mircea Trif and Pascal Simon, Phys. Rev. B 92, 014503 (2015).
[8] O. Parlavecchio et al, Phys. Rev. Lett. 119, 137001 (2017).  
5
Feb '18
Sateesh Mane  -  Monday, February 5, 2018
Relativistic Spin Polarized Beams in Accelerators
Computer Science, Queens College
ABSTRACT: This talk will present an overview of the subject of relativistic spin polarized beams in particle accelerators. The focus will mainly be high energy accelerators (such as RHIC at Brookhaven National Lab), but lower energy machines for nuclear physics will also be discussed. Highlights such as the precision measurement of the mass of the Z0 boson at CERN will be treated.

http://iopscience.iop.org/article/10.1088/0034-4885/68/9/R01/pdf
26
Feb '18
Aditi Mitra  -  Monday, February 26, 2018
ABSTRACT: Recent advances in ultra-fast measurement in cold atoms, as well as pump-probe spectroscopy of K3C60 films, have opened the possibility of rapidly quenching systems of interacting fermions to, and across, a finite temperature superfluid transition. However determining that a transient state has approached a second-order critical point is difficult, as standard equilibrium techniques are inapplicable. We show that the approach to the superfluid critical point in a transient state may be detected via time-resolved transport measurements, such as the optical conductivity. We leverage the fact that quenching to the vicinity of the critical point produces a highly time dependent density of superfluid fluctuations, which affect the conductivity in two ways. Firstly by inelastic scattering between the fermions and the fluctuations, and secondly by direct conduction through the fluctuations. The competition between these two effects leads to non-monotonic behavior in the time-resolved optical conductivity, providing a signature of the critical transient state
5
Mar '18
Donald Weingarten  -  Monday, March 5, 2018
Quantum Mechanics and the Macroscopic World
Indiana University, IBM Research, Finance
19
Mar '18
James Wynne  -  Monday, March 19, 2018
Illuminating My Career: From Flash Gordon to Laser Surgery
IBM Research Laboratory, Yorktown Heights
ABSTRACT:
The ruby laser first "lased" in May, 1960. It was used for retinal surgery in late 1961. Over the next two decades, many laser surgical procedures were developed to remove undesirable tissue or seal bleeding ulcerated tissue, but they all left "therapeutic" scar tissue. 
 
In Nov-Dec, 1981, my IBM colleagues and I discovered that the short pulses of energetic ultraviolet light from an ArF excimer laser, emitting at 193nm (6.4 eV), could produces ultra-clean incisions in animal tissue, in vitro. We conceived that this laser could incise living tissue, which might heal without scarring, because there would be minimal damage to the tissue underlying and adjacent to the incision. Collaboration with ophthalmologists led to the laser refractive surgical procedures known as LASIK and PRK, which have improved the vision of more the 40 million people.
 
In 1983, my colleagues and I discovered that blood absorbed the 6.4 eV light from the ArF excimer laser via a non-thermal process. We thought this meant that we could not use the laser to treat deep skin lesions. 26 years later, in 2009, my dermatologist colleague and I conceived of using the laser as a "smart scalpel" to debride necrotic lesions of the skin, such as burn eschar, leaving the underlying and adjacent viable skin undamaged, resulting in faster healing, less pain, and minimizing scar tissue formation, when compared to "cold steel" debridement. I will report on the latest results of my collaboration with dermatologists at Stony Brook University, where we burn live pigs, debride the necrotic tissue with the ArF excimer laser, and see enhanced healing. Our first peer-reviewed paper, "ArF excimer laser debrides burns without destruction of viable tissue: A pilot study," is In Press, available online, and will be published In Print in the next issue of BURNS.
 
26
Mar '18
Yuhang Ren  -  Monday, March 26, 2018
ABSTRACT: Recently, BaZr0.2Ti0.8O3 (BZT) based ferroelectric films have exhibited high energy storage densities (up to 166 joules per cubic centimeter) and recycling efficiencies (up to 96 percent). Here, I will introduce you our new investigation of heterophase polydomain structures in BZT films by optical second harmonic generation (SHG) and photo-induced acoustic waves. We analyzed the spatial distribution of SHG intensities and GHz acoustic phonon oscillations. A rhombohedral symmetry is revealed to grow with increasing film thickness as tetragonal domains relax away from the film-substrate interface. The presence of phase segregated tetragonal and rhombohedral structures is further confirmed through TEM and XRD measurements. The high energy performance of the films is explained by ultra-adaptive nanodomains which can effectively accommodate the competing elastic and electrical stress fields during charge-discharge cycles.
 
9
Apr '18
Dimitrios Sounas  -  Monday, April 9, 2018
Nonreciprocal photonics without magnetic biasing
The University of Texas at Austin
ABSTRACT: Reciprocity is a fundamental principle in optics, requiring that the response of a structure is symmetric when source and observation points are interchanged. It is of major significance for the analysis, design and operation of optical systems, but at the same time it poses fundamental limitations on the ways we handle and process optical signals. Nonreciprocal devices, which break this symmetry, have become fundamental in photonic systems for protection of lasers, the separation of signals propagating in opposite directions and the design of photonic topological insulators. Yet, to date they require magnetic materials, making them bulky, costly and unsuitable for integration. This is in stark contrast with most photonic devices, including sources, modulators, switches, waveguides, interconnects and antennas, which may be realized at the nanoscale. In this talk I will show how it is possible to address this problem and design magnetless nonreciprocal devices by using time modulation and nonlinear effects. I will discuss how time modulation allows to impart an effective momentum to a structure and break reciprocity. I will show how this approach can be implemented at different frequency bands, spanning from microwaves to optics. Then, I will present how we can completely remove the requirement of an external bias and realize all-passive nonreciprocal devices by introducing nonlinearities in asymmetric structures. I will discuss fundamental limitations of these devices, stemming from time-reversal symmetry, and show how they can be overcome. I will conclude my talk by providing an outlook for future opportunities of this rapidly advancing research field.
16
Apr '18
Viktoriia Babicheva  -  Monday, April 16, 2018
ABSTRACT: Optical metamaterials are three-dimensional structures with rationally designed building blocks that enable devices with distinct optical responses not attainable with naturally available materials. Comprising a class of metamaterials with a reduced dimensionality, optical metasurfaces allow the miniaturization of conventional refractive optics into planar structures, and a novel planar technology is expected to provide enhanced functionality for photonic devices being distinctly different from those observed in the three-dimensional case. In this talk, I will show that nanostructures made of high-index materials, such as silicon, transition metal dichalcogenides, or hexagonal boron nitride, support optically induced both electric and magnetic resonances in the visible and infrared spectral ranges. I will present the results on antireflective properties of metasurfaces based on high-index nanoparticle arrays and explain how zero backward scattering from the highly reflective substrate can be achieved [1]. Scattering-type scanning near-field optical microscope (s-SNOM) provides optical, chemical, and structural information of metasurfaces and enables their imaging with nanoscale resolution. I will show an approach to analyze layered of materials with different permittivities and demonstrate a technique to identify material type based on near fields at sample edges [2]. The recent discovery of high-index materials that offer low loss and tunability in their optical properties as well as complementary metal-oxide-semiconductor (CMOS) compatibility can enable a breakthrough in the field of nanophotonics, optical metamaterials, and their applications.

[1] V.E. Babicheva and A.B. Evlyukhin, "Resonant Lattice Kerker Effect in Metasurfaces with Electric and Magnetic Optical Responses," Laser & Photonics Reviews 11, 1700132 (2017).
[2] Y. Abate, S. Gamage, L. Zhen, S.B. Cronin, H. Wang, V. Babicheva, M.H. Javani, M.I. Stockman, “Nanoscopy reveals surface-metallic black phosphorus,” Light: Science & Applications 5, e16162 (2016).
 
18
Apr '18
Mohammad Ali Miri  -  Wednesday, April 18, 2018
ABSTRACT: This talk will describe several opportunities for realizing novel nanophotonic devices by employing new degrees of freedom including optical gain and loss as well as mechanical motion. Although most previous efforts on designing photonic devices and structures have been focused on crafting their refractive index profile while avoiding active and dissipative mechanisms, recent investigations suggest the use of such non-conservative processes in order to achieve unusual properties and functionalities. These recent theoretical developments, which are originally inspired by quantum mechanics, have led to the emerging area of non-Hermitian photonics, proposing the conjunctive use of the optical refractive index, gain and loss as three ingredients for photonics design.

In the first part of this talk, I will provide an overview of the fundamental concepts of non-
Hermitian photonics, discuss some of its unique and exotic phenomena and mention potential applications. In particular, I will discuss coupled active/passive resonators and introduce a versatile approach for enforcing single-mode operation in multi-mode laser cavities. The second part of this talk is devoted to micro-/nano-optomechanical cavities as rich platforms for establishing a dynamical coupling between the electromagnetic field and mechanical motion. I will discuss the dynamics of such devices and show that giant optomechanically-induced nonlinear effects, in connection with the optical and mechanical dissipation, offer a viable route for breaking the reciprocity of light in order to realize compact optical isolators and circulators.
23
Apr '18
Xi Chen  -  Monday, April 23, 2018
Evaporation-Driven Engines and Generators
CUNY Advanced Science Research Center
ABSTRACT: Evaporation, which fuels rain and wind, is one of the largest energy flows on Earth. While we can now access many energy sources powered by evaporation, such as hydropower and wind power, the upstream energy of natural evaporation still remains untapped. Water-responsive materials that swell and shrink in response to changes in humidity level can convert evaporation energy into mechanical energy. Bacillus spores are one example of water-responsive materials developed by nature. Our recent study shows that the energy density of spores is significantly higher than all existing actuator materials and artificial muscles. Using spores, we developed two kinds of evaporation-driven engines that can self-start and continuously convert evaporation into mechanical motions, and subsequently into electricity, when placed at air-water interfaces. The energy harvested from evaporation is enough to power a small light source as well as a miniature car.
30
Apr '18
Jack Harris  -  Monday, April 30, 2018
ABSTRACT: Topological phenomena appear in a number of systems, from exotic quantum phases to carefully engineered waveguides. They offer potentially powerful forms of control, and are intriguing in their own right. I will describe a topological feature that is generically present in one of nature's simplest systems: a pair of damped coupled oscillators. I will describe experiments in which we demonstrate this Moebius-strip-like feature and use it to achieve topological control over the excitations in an optomechanical system. I will also describe the nonreciprocal dynamics associated with this feature.
7
May '18
Anthony Pullen  -  Monday, May 7, 2018
ABSTRACT: Emission from ionized carbon, or CII emission, is a promising candidate for tracing the universe through intensity mapping.  In this talk I discuss my latest work, searching for this nearly isotropic CII emission from star-forming galaxies.  After giving an brief introduction to intensity mapping, I will motivate the use of CII intensity mapping  to probe cosmology and galaxy physics.  I will then present the constraints I constructed on CII emission through intensity-galaxy cross-correlations, as well as current research to improve these constraints.  Finally, I will present EXCLAIM, a proposed balloon experiment, of which I am a part, that will aim to map CO and CII emission for studying star formation.
25
Jul '18
Sylvain Gigan  -  Wednesday, July 25, 2018
Optical wave propagation in complex media: from pulse shaping to an invariance of the path length
Sorbonne Université Kastler-Brossel Laboratory, Collège de France
ABSTRACT: Scattering of light in heterogeneous media, for instance the skin or a glass of milk, is usually considered an inevitable perturbation or even a nuisance. Through repeated scattering and interferences, this phenomenon seemingly destroys both the spatial and the phase information of any laser illumination. At the spatial level, it gives rise to the well-known “speckle” interference patterns. At the temporal (or spectral) level, a short pulse entering a scattering medium will see its length greatly extended due to the multiplicity of possible path length light can take before exiting the medium. From an operative point of view, scattering greatly limits the possibility to image or manipulate an object with light through or in a scattering medium. Multiple scattering is nonetheless an invaluable field of research for experimentalists and theoreticians alike, at the crossing of optics, condensed matter physics, statistical physics, chaos, to name just a few. 

Multiple scattering is a highly complex but nonetheless deterministic process: it is therefore reversible, in the absence of absorption. Speckle is coherent, and can be coherently controlled. By « shaping » or « adapting » the incident light, it is in principle possible to control the propagation and overcome the scattering process. I will show our recent results on achieving a complete pulse control (spatial and temporal) by means of wavefront shaping. I will also show the experimental demonstration of a peculiar property of light in disorder, namely that the mean path length is independent of the disorder strength. 
31
Aug '18
Silas Hoffman  -  Friday, August 31, 2018
ABSTRACT: Spin superfluids enable long-distance spin transport through classical ferromagnets by developing topologically protected defects in the magnetic texture. For small spins, in which the magnetization takes quantized values, the topological protection suffers from strong quantum fluctuations. We study the remanence of spin superfluidity inherited from the classical magnet by considering the two-terminal spin transport through a finite spin-1/2 ferromagnetic chain with planar exchange. In the absence of anisotropy in the exchange or an applied magnetic field, the spectrum is gapless. There exist zero-energy domain-wall modes that rotate within the plane of the exchange interaction and are the analogue of the topological defects found in classical magnets. If the system is ordered by an exchange anisotropy, the spectrum is gapped and there exist zero-energy modes localized to the ends of the ferromagnetic chain which are guaranteed by topological properties of the bulk spectrum. We find zero-energy domain-walls, polarized perpendicular to the anisotropy, incident on an ordered chain are reflected as domain-walls polarized in the opposite direction. Furthermore, a domain-wall polarized within the plane of the exchange can be ballistically transmitted through the same magnetic chain of a resonant length. This resonant length depends linearly on the applied magnetic field so that, for a fixed length of chain, the transmission of domain-walls can be tuned by the magnetic field.
17
Sep '18
Misha Sumetsky  -  Monday, September 17, 2018
Localization of light in an optical microcapillary induced by a droplet
Aston University, Institute of Photonic Technologies
ABSTRACT: We show experimentally and theoretically that whispering gallery modes in a silica microcapillary can be fully localized (rather than perturbed) by evanescent coupling to a water droplet and, thus, form a high-quality-factor microresonator. The spectra of this resonator, measured with a microfiber translated along the capillary, present a hierarchy of resonances that allow us to determine the size of the droplet and variation of its length due to the evaporation. The discovered phenomenon of complete localization of light in liquid-filled optical microcapillaries suggests a new type of microfluidic photonic device as well as an ultraprecise method for microfluidic characterization.
24
Sep '18
Alex Krasnok  -  Monday, September 24, 2018
Novel aspects of light scattering
Advance Science Research Center and Graduate Center, CUNY
ABSTRACT: Scattering of electromagnetic waves lies in the heart of the most experimental techniques in radiophysics, visible and X-ray optics that allow us to investigate the micro- and nanoworld. Recently, a wide spectrum of exceptional scattering effects attainable in carefully engineered structures have been predicted and demonstrated. In my talk, I will present our recent results on novel aspects of light scattering including coherent virtual absorption, coherently enhanced WPT, and strong coupling regime in excitonic systems.
15
Oct '18
Larry Liebovitch  -  Monday, October 15, 2018
22
Oct '18
Miriam Rafailovich  -  Monday, October 22, 2018
5
Nov '18
Andrea Alù  -  Monday, November 5, 2018
New frontiers for light control and manipulation using metamaterials
Advanced Science Research Center and Graduate Center, CUNY
ABSTRACT: Metamaterials are artificial materials with properties well beyond what offered by nature, providing unprecedented opportunities to tailor and enhance the interaction between waves with materials. In this talk, I discuss our recent research activity in electromagnetics, nano-optics and acoustics, showing how suitably tailored meta-atoms and arrangements of them open exciting venues to manipulate and control waves in unprecedented ways. I will discuss our recent theoretical and experimental results, including metamaterials for scattering suppression, metasurfaces to control wave propagation and radiation, large nonreciprocity without magnetic bias, giant nonlinearities in properly tailored metamaterials and metasurfaces, and active metamaterials. Physical insights into these exotic phenomena, new devices based on these concepts, and their impact on technology will be discussed during the talk.
12
Nov '18
Nikodem Poplawski  -  Monday, November 12, 2018
ABSTRACT: The conservation law for the total (orbital plus spin) angular momentum of a Dirac particle in the presence of gravity requires that spacetime is not only curved, but also has a nonzero torsion. The coupling between the spin and torsion in the Einstein–Cartan theory of gravity generates gravitational repulsion at extremely high densities, which prevents a singularity in a black hole and may create there a new, closed, baby universe undergoing one or more nonsingular bounces. We show that quantum particle production caused by an extremely high curvature near a bounce creates enormous amounts of matter and can generate a finite period of inflation. Our scenario has only one parameter, does not depend significantly on the initial conditions, does not involve hypothetical scalar fields, avoids eternal inflation, and predicts plateau-like inflation that is supported by the Planck observations of the cosmic microwave background. This scenario suggests that our Universe may have originated from a black hole existing in another universe.
26
Nov '18
Ivan Corwin  -  Monday, November 26, 2018
A drunk walk in a drunk world
Columbia University
ABSTRACT: We will consider the effect of a space-time random environment of jumping probabilities on a collection of independent random walkers. Surprisingly, the extreme value behavior for these walkers is governed by the Kardar-Parisi-Zhang universality class which arises in random growth models and random matrix theory. No background of any of these subjects will be assumed.
3
Dec '18
Demetrios Christodoulides  -  Monday, December 3, 2018
Thermodynamics of nonlinear multimode fibers
University of Central Florida, CREOL
10
Dec '18
Eleana Makri  -  Monday, December 10, 2018
ABSTRACT: Photonic limiters are protection devices which transmit electromagnetic radiation at low-level incident intensity while blocking high-intensity electromagnetic signals. Passive limiters typically block excessive radiation by means of absorption, which can often cause their destruction due to overheating. We propose the design of a reflective limiter based on resonant transmission through a defect localized mode. The benefit of this design is that it offers protection by reflecting the excessive radiation instead of absorbing it, which reduces overheating problems and results in a device with an extended dynamic range. In this talk, I will present implementations of this idea in band-gap systems in (i) the infrared domain, based on multilayer photonic crystals, and (ii) the microwave domain, based on chiral or CT symmetric coupled resonator waveguide arrays.