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Nov 05

By Lynn Savage

What does it take to become a VIP of the research world — someone who, to most people, is miles ahead of anyone else in their scientific field? For the average citizen of the world, these things are measured by awards — not the number, but which ones.

Among all of the myriad ways a scientist may come into a modicum of public attention, none is more prominent than the Nobel Prize. Although there has been the occasional controversy throughout the century-plus that the Nobels have been awarded, winners of the Physics, Chemistry, and Medicine prizes well represent the drive, patience, hard work, and creative spark needed to break ground for entire new realms of discovery and progress.

Perhaps not too amazingly, the field of photonics has been extraordinarily well represented lately by Nobel Prize winners. In the past decade, the Royal Swedish Academy of Sciences has deemed worthy of a Prize several light-driven discoveries, ranging from the creation of the charge-coupled device (CCD) to development of the quantum theory of optical coherence, and from the discovery and development of green fluorescent protein to the establishment of novel ways to see beyond the diffraction limit with powerful microscopes.

Amazingly, CLEO: 2015 will provide attendees the opportunity to hear no fewer than four Nobel Prize winners describe their research during the Plenary Session: Eric Betzig, Steven Chu, Hiroshi Amano, and Shuji Nakamura.

Eric Betzig, a co-winner of the Nobel Prize Winner in Chemistry in 2014, will discuss his work in the field of super-resolution fluorescence microscopy. A member of the Howard Hughes Medical Institute’s Janelia Farm Research

Eric Betzig

Eric Betzig, 2014  Nobel Prize Winner

Campus in Ashburn, Virginia, USA, Betzig will describe three distinctly different super-resolution microscopy techniques in his talk, “Imaging life at High Spatiotemporal Resolution.”

Betzig will focus on ways he and other researchers continue to seek ways to improve the ability of optical microscopes to see the most minute features of tiny biological structures. To exceed the formidable threshold of the diffraction limit of 200 nm, microscopists must juggle spatial resolution, speed and non-invasiveness. Betzig and his colleagues first broached the 200-nm resolution mark with a technique they dubbed photoactivated localization microscopy (PALM), one of the first successes at using fluorescent molecules to illuminate neighboring targets of interest to the viewers, such as individual cells. Betzig’s work earned him a share of the chemistry Nobel with Stefan W. Hell of Max Planck Institute for Biophysical Chemistry in Gottingen, Germany, and William Moerner of Stanford University in California, USA.

Steven Chu of Stanford University, California, USA, the US Secretary of Energy from 2009 to 2013, was also a Nobel Prize Winner. He, Claude Cohen-Tannoudji and William Daniel Phillips were awarded the Physics Prize in 1997 for their work with laser-based cooling and trapping of atoms. In his plenary discussion, “Microscopy 2.0,” Chu will explore the evolution of imaging techniques that have improved biologists’ understanding of living systems at the level of genes and proteins.

According to Chu, “the visualization of the structure of DNA by Watson and Crick led [to] a true understanding of the concept of genes, transcription, and translation. In recent years, the invention of new imaging technologies is having a profound impact on biological sciences.”


Hiroshi Amano, 2014 Nobel Prize Winner

Hiroshi Amano of Nagoya University, Japan, and Shuji Nakamura of the University of California, Santa Barbara, won (alongside Isamu Akasaki of Meijo University in Nagoya, Japan) the 2014 Nobel in Physics for work that gave the world blue light-emitting diodes. This was a culminated effort as complex as it is important to many industries, and Amano and Nakamura will lead discussions on the ultimate value to society of LED-based technology.

Amano’s talk, “Current and Future of Solid-State Lighting” will provide an overview of the technology and relate several of the ongoing technical challenges remaining to be solved. Nakamura will discuss the ways in which LED lighting systems can reduce global energy demand in his talk, “Energy Savings by LED Lighting.”

In addition, Tony Heinz of Columbia University in New York City, USA, will discuss “Electrons in Atomically Thin Two-Dimensional Crystals,” referring to graphene. He will describe the state-of-the-art of these 2-D lattices of carbon atoms, including the known properties of electrons confined to this single-atom-thick material, the interactions of light and matter along the surface of a sheet of graphene, and some of the potential applications for devices made of the material, which can work with wavelengths from UV to THz. He will also expand the discussion into other materials that have peculiar yet useful properties when made into monolayers, including dichalcogenides.

Nobody yet knows where the next Nobel-worthy effort will originate, but with all of the excitement being generated by optical and photonic research it doesn’t take a genius to keep looking toward the light.




Sep 08

By Lynn Savage

While I am sure that some people find that attending conferences can be a bit of a chore – something to get done as soon as possible before heading back to “real work” – that has never been true for me. And I don’t know you very well, but I’m guessing conferences aren’t a burden to you either, given that you’re here, reading about one that won’t arrive for months.

Of course, the one that we’re here to discuss is CLEO, one of the liveliest of all industry shows (and not just in the photonics industry). I’ll admit that I have a soft spot for CLEO; it was my first photonics conference ever (Baltimore, 2005, if you’re keeping score). The constant buzz of activity in the venue included a whirl of people and technologies that insisted on constant engagement. Academic researchers making last-minute adjustments to their presentations, post-docs

Technologies being showcased at CLEO

Technologies being showcased at CLEO

seeking their assigned spot in the poster area, salespeople seeking places to converse with clients, marketing reps setting up trade show booths, CLEO management show-runners scrambling to make sure everything from registration to AV tech to the coatrooms were operating smoothly — everyone with their individual missions and goals, gathered together to make sparks fly. It was a heady mix for any first timer, but I was thrilled to be there and dive in with my own, journalistic, goals.

Although my current avocation is science journalism, it has come via a path that began when I first trained to become a mechanical drafter. Although this never became a career, I really enjoyed the design process and the meticulous way one must consider form and function when laying designs out on paper. One of my favorite things about being a student of the drafter’s craft, though, was perusing catalogs filled with mechanical devices, from simple screws and bolts to advanced tools and heavy machinery. These catalogs informed me of a larger world of invention and craftsmanship that I wanted to tap into.

So, as exciting as it is to hear about advances in basic science and perhaps-someday-feasible technologies coming out of academic, government, and commercial laboratories around world, seeing the best of the lot make their way into the “real” world of applications is, frankly, often thrilling. It’s like watching your favorite minor league ballplayer break into the big leagues, finally earning a chance to swing the bat against the Clayton Kershaws of the world.

To support the idea that exciting developments are happening on the path from lab to market, CLEO is looking for even more input in 2015 from optical engineers, the people who take promising research results and translate them into amazing products.

For CLEO: 2015, the CLEO team is looking for presentations that will delight and inspire future developments, making sure that there is a steady spotlight on the pipeline of innovation in the optics and photonics world. Specifically, the organization hopes to see submissions in the following areas:

Biomedical applications

  • Biomedical spectroscopy, microscopy, and imaging
  • Neurophotonics and brain activity monitoring
  • Optogenetics and optical control of cells
  • Light sources and devices for biomedical imaging
  • Clinical technologies and systems

Industrial applications

  • New laser sources for industrial use
  • Micro/nanoprocessing and manufacturing
  • Sensing and process control
  • Ultrafast lasers

Photonic instrumentation and techniques for metrology and industrial processes 

  • Chemical sensing
  • Security applications
  • Process monitoring
  • Metrology

Lasers and photonic applications to energy and environment

  • New energy sources
  • Solar energy systems
  • Photonic instrumentation for energy and environment

CLEO is specifically seeking stories of evolving engineering efforts, including both maturing and already-implemented photonics technologies. Especially desired are introductions to and demonstrations of new products (without an accompanying overt sales pitch) or existing products with new capabilities; optical technologies at work in field situations, such as advanced sensors, metrology systems and the like; novel technologies useful to material fabricators and manufacturers; optical technologies useful in the design of system controls; and clinical applications of new or improved photonics-based sensors, cutting tools, or therapeutic approaches. The Society also is seeking exhibitions of optical engineering, especially hardware with new or significantly improved sensors, optical components and subsystems, optical designs for optical or electro-optical systems and subsystems; novel (or advancements to existing) optical system control/processing algorithms that enable new technical capabilities; new optics designs and measurement techniques; and advanced optics-based diagnostics systems.

Submitted papers are reviewed, with an eye toward “uniqueness, impact of the work, and how the work advanced the state of the art.”

So, if you have a choice bit of technology you’d like to show off to a wide-eyed group of people at next year’s meeting, heed the call for papers (http://www.cleoconference.org/home/submissions/) being requested by CLEO. The deadline is 16 December at 17.00 GMT.


Aug 27

Read about the latest advances in  Low Level Light Therapy (LLLT) also known as photobiomodulation (PBM), as presented at the OSA Incubator held in August.

By Guest Blogger, Elieza Tang, The Optical Society Blog

LLLT/PBM describes the use of light therapy in the visible and near-infrared spectrum for stimulating biological responses. Extensive laboratory experiments and clinical trials have demonstrated PBM to be efficacious in tissue regeneration including the skin, muscle, nerves, bone, spinal PBM has been shown to produce an analgesic effect, anti-inflammatory effect and promote angiogenesis. The results from these controlled clinical trials and laboratory studies provides

Low light therapy example

Low light Therapy

exciting and convincing evidence for the use of PBM as an efficacious, noninvasive treatment modality in the clinical setting. Many of these studies have demonstrated improved results and recovery with conditions such as traumatic brain injury, chronic wounds, spinal cord injury and many other injury models.However, PBM has yet to be adopted by mainstream medicine. Why you ask? There are different answers based on who you ask. Read More »

The full 3 part blog series covering the technology presented at the Low Level Light Therapy Incubator can be found on The Optical Society Blog.


Jun 23

By Guest Blogger, Liu Yuxiang

So much went on a CLEO:14! Here are two highlights.


Sang Min, National Institutes of Technology (NIST), discussed scanning probe imaging based on a cavity optomechanical sensors (SF2M.7) and the images were compared with conventional AFM images. This work shows great potential for on-chip AFM devices, which have a footprint of tens of microns and are fully compatible with silicon micro-/nanophotonic devices.


Prof. Bolger Schmidt, University of California, Santa Cruz, discussed recent progress of microfluidics based photonic devices and hybrid integration of electro-opto-fluidic devices (AF2L.4). Particularly, reconfigurable optofluidic devices can simultaneously manipulate and sense micro/nanoparticles. In addition, nanopores in microfluidic chips have been used to carry out single nanoparticle sensing down to the size of 30 nm.


Jun 14

By Howard Lee

The poster sessions that I have attended over last 3 days at CLEO have been great (the only recommendation I might add is that it would have been really nice  if they taken place closer towards the end of the day). The quality of the posters are very high, I enjoyed them immensely.

Another important highlight of the conference today was the postdeadline session where scientists present their latest and most impressive results in a 10 minute time frame. Here are a few that I heard:

Optical Broadband Angular Selectivity (JTH5B.2)

Yichen Shen from MIT presented their results on achieving broadband angular selectivity of light. The principle behind is to use the generalized Brewster angle by making 1D photonic crystal (multilayer structure made with SiO2 and Ta2O5) with different periodicity. He showed that a complete transparency of the structure at only one angle and the light reflects at other angles. The works are published at Science 343, 1499 (2014).

Silicon-Chip Mid-Infrared Frequency Comb Generation (STH5C.6)

Researcher from Cornell presented a first on-chip integrated mid-infrared frequency comb with 750nm-wide comb centered at 2.6um. Due to the large nonlinear loss of silicon from the three-photon absorption followed by free carrier generation, it was typically difficult to generate an efficient comb at mid-infrared region using silicon waveguide. The design of silicon waveguides with a ring resonator embedded in a PIN structure significantly reduce the free carrier lifetimes and allow the generation of mid-infrared frequency comb for the first time (see figure below).

Silicon-Chip Mid-Infrared Frequency Comb Generation

(Top) Optical microscope image of ring resonator with metal contacts and false colored SEM image of the silicon waveguide, doped regions, and metal contacts. Inset: simulated optical mode at 2.6 um, showing highconfinement. (Bottom) FTIR scans showing the full extent of the MIDIR frequency comb (corrected for the filters spectral response). [STH5C.6]

Gain from Helium-Xenon Discharges in Hollow Optical Fibres at 3 to 3.5 um (STh5C.10)

Researchers from Bath University discussed the first detected gain on laser transition in hollow core photonic crystal fiber gas discharges. They used an anti-resonant guided hollow core fiber for this discharge experiment as this fiber allow good transmission in IR range. They used fiber with length between 0.5-1m and high DC voltage up to 40kV to discharge the Helium-Xenon gas inside the fiber. They observed strong emission line from the discharge and found that the emission was stronger with longer fiber length, indicting the presence of net gain from the discharge. Their goal of the project is to make the first electrically excited fibre-based gas laser.

Gain from Helium-Xenon Discharges in Hollow Optical Fibres at 3 to 3.5 um Experimental setup. b) Signal in a 20 nm bandwidth at 3.5 μm, with discharge current 0.25 mA at 12 mbar pressure, for different lengths Inset: Optical micrograph of the fibre. Spectra for 1 m length (solid) and 0.5 m length (dashed) discharges with a discharge current of 0.25 mA and 20 nm resolution. (STh5C.10).

This has really been an enriching experience with great research in a number of areas.  I look forward to seeing everyone next year, 10-15 May 2015.

Jun 12

By Howard Lee

I was happy to spend most of my time today at several CLEO events; Plenary talk, technical talks, poster session and market focus. This morning’s Plenary session  was on the topic “Fibres and the future” by David Payne. Prof. Payne  gave a great overview on the works of fiber amplifier. Using cladding-pumped microsturctured fiber, amplifier with high output power at telecommunication wavelength or IR can be realized. Prof. Payne also suggested an idea that these kinds of fiber-laser would be designed as a powerful laser for next accelerator for CERN! This idea may be realized by using array of fiber lasers combined with multicore fibers to confine to a high power output laser and finally delivery by hollow core bandgap fiber.

I also attended another nice tutorial talk in the morning given by Prof. Nikolay Zheludev (University of Southampton) on “Optical Properties on Demand: Reconfigurable and Coherently Controlled Metamaterials” (FW1K.1). Prof. Zheludev starts his presentation by comparing the citation number between metamaterial and laser (when it was starts invented in 1962), showing the rapid development on the field of metamaterial since 2000 (see figure below). He then pointed out the importance of developing tunable and reconfigurable metamaterials, in which would allow precise control of electromagnetic responses of the materials at nanometer scale. He presented several new materials of metamaterials (e.g., grapheme, nitride, conducting oxide, silicon and topological insulator) and tunable mechanisms studied by his group and other groups. One particular important example of reconfigurable metamaterial he presented is utilizing electromagnetic force (Lorentz force) to functionalize the metadevice (see structure below). Finally, he mentioned three “killer applications” which metamaterials would potential take place: 1) tunable lasing spaser, 2) mobile dynamic 3D display and 3) space division multiplexing in fiber networks. After the talk, I talked to Prof. Zheludev and asked him how would we keep growing the field of metamaterial and impacting our life using metamaterial as what the laser can do. He said that everyone working in this field (metmaterials) should work hard and one day we will see the high impact of metamaterials.

The next photonic revolution: Metamaterials

(Images: Courtesy of Nikolay Zheludev) (FW1K.1) http://www.nanophotonics.org.uk/niz/niz_talk.pdf

The MarketFocus: The Future of “Enabling” Photonics Innovation at 2-4pm today is an interesting event. As mentioned in the previous posts by Shamsul Arafin, there are a lot of discussions on how to enable photonics technology, including the support required from industry, academic university and government. To summarize the event, the chair Jason Eichenholz (CEO, Open Photonics Inc) asked the panel speakers what will be most important area of photonics for the next 15 years. Different speakers have different opinions, but  health care, security, energy recourses (e.g. solar energy), vision (sensing, imaging) and environmental issue (e.g. clean water) are the top  areas where they think photonics can play a high impact role in the near future. Nevertheless, the government support is one of the most important issues on enabling photonic innovation.

By the way, if you are OSA student, I suggest you to have a look at the OSA student membership booth. What they (OSA) provide you is the set of “big bang theory” where you can get some coffee, relax a bit or even play table tennis on the optical table. Also, there are some free OSA T.shirts and Newport snacks. So I hope you get the chance to check it out!

The OSA Student Lounge

Two more days to go till the end of CLEO conference; so take your time to learn as much as you can  these last two days!




Jun 12

By Sheng Liu

Note: Most of the following materials are cited from the material distributed in the meeting

On June 2, 2014, Department of Defense (DoD) announced a Request for Information (RFI) Institutes for Manufacturing Innovation, RFI-RQKM-2014-0022.

The DoD wishes to consider input from Industry and Academia as part of an effort to select and scope the technology focus areas for future Institutes for Manufacturing Innovation (IMIs). These IMIs will be regionally centered Public Private Partnerships enabling the scale-up of advanced manufacturing technologies and processes with the goal of successful transition of existing science and technology into the marketplace for both Defense and commercial applications. Each Institute will be led by a not-for-profit organization and focus on one technology area. The Department is requesting responses which will assist in the selection of a technology focus area from those currently under consideration, based upon evidence of national security requirement, economic benefit, technical opportunity, relevance to industry, business case for sustainability, and workforce challenge.

The Technical Focus Areas currently under consideration are:

  • Flexible Hybrid Electronics
  • Photonics
  • Engineered Nanomaterials
  • Fiber and Textiles
  • Electronic Packaging and Reliability
  • Aerospace Composites

Therefore, optics and photonics will be competing directly with other technology areas for a possible DoD-sponsored IMI.

The opportunity to form a new IMI for photonics would benefit the entire industry by focusing federal and private sector investment and innovation through collaboration. The DoD is committing $70 million in federal funds with a minimum 1:1 non-federal cost share. Securing an IMI would confirm the importance of optics and photonics to the future of American manufacturing and the American work force, and it would continue to reinforce the foundational role of optics and photonics in virtually all sectors of the economy.

Therefore, active responses from optics and photonics communities to RFI is very important!!!

THz Science and Spectroscopy

While THz spectroscopy has served as an extremely useful tool for probing carrier dynamics for decades, it still surprises us today how far THz technology can extend to. There are two sections that researches presented their work on the generation of strong THz field (SW1F) and how THz are used for spectroscopy and sensing (SW3F).
Rupert Huber group from University of Regensburg continue surprises us how the strong THz pulses (multiple 10 MV/cm) can perturb electronic structure. After publishing the work of using 72 MV//cm THz pulse to drive coherent interband polarization combined with dynamical Bloch oscillations in semiconducting gallium selenide (generating phase-stable high-harmonic transients, covering the entire terahertz-to-visible spectral domain between 0.1 and 675 THz), today they present photoluminescence of GaAs driven by THz pulses which is only 1/400 photon energy of the bandgap of GaAs.

THz Science and Spectroscopy
(this figure comes from http://www.nature.com/nphoton/journal/v8/n2/full/nphoton.2013.349.html)

Tobias Kampfrath from Fritz Haber Institute reviewed the progress of strong THz radiation resonantly and sensitively probing electron transport, spin precession and ion vibration in solids in the past few years. Strong THz radiation indeed serves as a powerful tool for us to explore the most fundamental physics.

Jun 12

Since it’s a topic that’s close to my heart, I enjoy the opportunity to see the latest work on semiconductor lasers whenever I come to CLEO. As always, I have been very impressed by all the work I’ve seen. And here I’d just like to highlight a couple of the many very impressive talks on this topic.

(a) Optical microscope image of the half-wave coupled rectangular ring-FP laser; (b) single mode emission with 44.5dB SMSR (Wu et al., CLEO 2014, STH1G.1).

(a) Optical microscope image of the half-wave coupled rectangular ring-FP laser; (b) single mode emission with 44.5dB SMSR (Wu et al., CLEO 2014, STH1G.1).

One that struck me is work out of Zhejiang University in China. The standard for tunable diode lasers is typically distributed Bragg reflector edge emitting lasers, and they’re remarkable devices. They’re capable of producing single-mode lasers with high side mode suppression, and, using some special tricks, can be tuned over a very wide bandwidth. The researchers at Zhejiang University, however, are taking a different approach. By coupling a ring resonator to a Fabry-Perot cavity, they get excellent wavelength selectivity (up to 41 dB of SMSR). In addition, they can selectively tune the device over a very wide bandwidth, achieving 50 channels on a 50 GHz spacing. It looks like a very interesting alternative to the conventional device.

Schematic of the device, (b) SEM picture of the first-order 50% duty cycle sidewall gratings with a 0.6 μm recess and λ/4 shift, (c) the MMI output side (Hou et al., CLEO 2014, STH1G.4).

Schematic of the device, (b) SEM picture of the first-order 50% duty cycle sidewall gratings with a 0.6 μm recess and λ/4 shift, (c) the MMI output side (Hou et al., CLEO 2014, STH1G.4).

Another interesting talk came out of University of Glasgow in the UK. These researchers have taking steps to monolithically scale up diode laser brightness. In order to do so, they have fabricated a DFB laser along with optical amplifiers. What’s special is that they’ve included intermediately a small tree of MMI splitters, so that an array of amplifiers exists at the device output. As a result, they get a coherently phased array with narrow divergence in the array direction and increased total power. The researchers demonstrated a four-element array, but they expressed hope for scaling up to even larger arrays in the near future. The nice thing is this sort of technology is scalable, and although there are some practical limits, there really aren’t any show-stopping fundamental limits to getting up to very high brightness sources.

These are just a couple of the remarkable talks on recent work in semiconductor lasers. Seeing as how fundamentally important diode lasers are to optical communications, sensing, research, and many other fields, it’s great to see the continued progress in this field.

Disclaimer: Opinions, interpretations, conclusions, and recommendations are those of the author and are not necessarily endorsed by the United States Government and MIT Lincoln Laboratory.

Jun 12

By Shamsul Arafin

On the Wednesday morning, CLEO 2014 started with an excellent plenary talk on Fibers and the Future given by the inventor of erbium-doped fiber amplifier, David Payne (University of Southampton, UK), which featured the recent advancements and developments of optical fibers and its associated technologies such as fiber lasers, modulators, detectors or its relevant applications in telecoms and sensing. In his presentation, he showed different type of novel fiber design concepts including multielement fiber, multi-core fibers, anti-resonant hollow core fibers and the pros and cons of each design in terms of the transmission capacity, cross-talk noise reduction capability and suitability of interconnection technologies.

After the Plenary Session, CLEO: Market Focus program continued like yesterday which provided a platform to discuss about Operational Strategies for the Laser and Photonics Industry. The session, conducted by, Scott Dunbar, (Chief Operating Officer, AdValue Photonics, USA), started with a reasonable number of audiences and primarily addressed four successful companies’ operational strategies which are mainly based on in-house vs external manufacturing and on-shore vs. off-shore manufacturing. The first presentation was made by Mark Holman (A.T. Kearney, USA), covering the value-chain, levels and abilities in outsourcing/off-shore manufacturing for the photonic components, the unique challenges to realize such components due to the necessity of sophisticated cleanroom/fabrication facilities, high-skilled workers, qualities, etc. compared to standard electronics as well as the best practices to ensure corporate success. The next speaker, Nat Mani (CEO, Bestronics, USA) described the merits and demerits of contract manufacturer (CM) vs original equipment manufacturer (OEM) and explained how his company has become successful out of in-house/ on-shore manufacturing strategies. Then Kurt Weingarten (JDSU, Switzerland) introduced the strategies for his Time-Bandwidth products, a provider of high-powered and ultrafast lasers for the industrial and scientific markets. Finally, Andrew Willse (Director of Director of DPSS operations, Coherent, USA) described the effectiveness of outsourcing/off-shore manufacturing strategies by introducing several operational best practices for a successful Dual-Factory implementation.

Look for more  information on hot topic research tomorrow.

Jun 11

In a recent Physics Today article, Mohammad Hafezi and Jacob Taylor reviewed their recent work on creating topological insulators for light (Physics Today, May 2014, p. 68, http://dx.doi.org/10.1063/PT.3.2394). One of the great things about CLEO is that this sort of cutting-edge research is commonly part of the program. And never failing to please, this year’s conference featured a couple of talks on this novel topic in photonic science.

First, let me review just a little bit about topological insulators as I understand them using (as Hafezi and Taylor did) the canonical example of the quantum Hall effect. The system under study is a two-dimensional material containing charged particles. If one applies a magnetic field perpendicular to the sheet, this will cause the particles to undergo circular orbits in the plane. In the center of the material, particles complete their orbits and globally remain stationary; the result is that there is no net transfer of charge and the material is insulating. However, something remarkable happens at the edges: the particles are unable to undergo a full rotation before ramming into a material wall. Then, instead of orbiting in place, the particle bounces off the wall and begins another partial rotation in the same direction. As a result, the particle hops along the edge of the material, and the effect is that there is charge transport and, therefore, a current. What you’re left with is a material that is insulating on the interior and conducting along the edges. The remarkable thing is that now researchers have observed this effect using photonics, and in more way that one!

In one realization presented at the conference, researchers from Technion Israel Institute of Technology and Friedrich-Schiller-Universitat Jena created a periodic array of helically shaped waveguides. The analog of photons propagating down the array of helical waveguides is electrons evolving in time in a lattice of circulating atoms. In this rotating frame, the result is similar to that described above: propagation in the bulk of the material is prohibited, whereas there are propagating states allowed at the edges. The talk gave many examples of how this worked and what could be done with it. For example, in a honeycomb lattice, there are types of edges that allow edges states and some that don’t. However, when the helical waveguides are used, the usually “non-conducting” edges begin to allow the propagation of light. What’s even more remarkable is that light that transits from one edge type to another at a corner does so without scattering; instead it just makes the 90-degree turn an continues its propagation. This is just a taste of some of the remarkable results discussed in this talk, and more can be found in the CLEO abstract and their recent publication (Rechtsman et al., Nature, vol. 496, p. 196, 2013).

The other topological insulator talk I had the privilege of seeing was given by a member of the group that published the Physics Today article. In their work, they realize a topological insulator by utilizing a 2D array of coupled ring resonators. As they note in their article, the important property that they honed in on is that the path length of light traveling in a clockwise direction should be different from that traveling counterclockwise. To achieve this, they made oblong ring resonators, rotated neighboring rings 90 degrees with respect to one another, and offset them from center. The result is that light traveling in one direction take a long-arm path, whereas the short path is taken in the other direction. By using such an arrangement, they showed that edge states can be excited by operating at the correct frequency where bulk propagation is disallowed. In addition, due to the path length asymmetry, propagation in different directions is excited at different frequencies. A very exciting result to be sure. Again, I’m certain I can’t do justice to all the remarkable results, but one can see their CLEO abstract or their recent publication (Hafezi et al., Nature Photonics, vol. 7, p. 1001, 2013).

To my knowledge, these are the only two demonstrations of photonic topological insulators to date. However, this is a very new and exciting field; the theory for photonic topological insulators is less than a decade old. It’s remarkable how quickly these experimental results have been realized. I’m sure we can look forward to even more exciting results in the near future, and I look forward to it.

Disclaimer: Opinions, interpretations, conclusions, and recommendations are those of the author and are not necessarily endorsed by the United States Government and MIT Lincoln Laboratory.

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