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Apr 30
Iain McKinnie, Lockheed Martin Advanced Technology Center,  CLEO: Applications & Technology 2013 Program Chair

Iain McKinnie, Lockheed Martin Advanced Technology Center, CLEO: Applications & Technology 2013 Program Chair

This year’s CLEO Conference, sponsored by APS/Division of Laser Science, IEEE Photonics Society and the Optical Society features an expanding Applications & Technology Program focusing on the core areas of Biomed, Energy, Industrial and Government/National Science and Security Standards.  Tom Giallorenzi, OSA’s Science Advisor interviewed Iain Mckinnie, Program Chair, Applications & Technology to delve further into some of this year’s hot topics.

Tom Giallorenzi: Can you say a little bit about technology transitions that this meeting is fostering?

Iain McKinnie:      “………there are many great examples in the Applications and Technology conference that you can see, including quantum cascade lasers.  We have a plenary talk this year which we’re very excited about by Dr. Kumar Patel from Pranalytica who is also a professor at UCLA.  And he’s going to be talking about how those quantum cascade lasers – now room temperature and multi-watt lasers in the midwave and long wave infrared region – are impacting applications from civil aircraft defense via countermeasures, through to trace gas detection for a range of commercial security  and environmental applications.  So that’s one capability that’s transitioning.

There are many more.  In the energy area, we’re looking at increasing transition of broadband nitride semiconductor materials in solar cells and in extending the spectral range of LEDs down into the UV region from the visible region. We’re also seeing increasing transition of ultrafast lasers, which continue to enable advances in manufacturing from the macro to the micro down to the nano scale.  ……. I think that we keep the wow factor in the conference also, and that comes in via big science; with some of the facility class laser systems: electron beams being used to generate extremely short bursts of intense light, and being used to generate extremely broadband, broad spectral access from the UV right out far into the infrared region.  Also, we have a big emphasis this year on the National Ignition Facility and the latest progress that they have achieved in the extreme high field regime.  So, you know, I think as well as things that could have mass market applicability, it’s important that we keep our finger on the pulse of the really impressive landmark advances at the unique and high power end.

Tom Giallorenzi: Can you say a few words about the special symposia?

Iain McKinnie:      One thing we’re very consciously focused on in 2013 at CLEO A&T is to bring in a number of special symposia which we believe represents a pretty broad suite of the application space for lasers that’s emerging.  I mentioned already the symposium related to the national ignition facility.  We have a number of others.  One that we’re excited about at the extreme other end of the scale is a lab on a chip symposium this year where we’re really taking advantage of advances not only in laser and LED sources, but also in microfluidics and nanotechnology and a whole lot of related applications to really take the pulse of that field and get a sense for how lab on a chip is advancing.

Beyond that, we also have a special symposium that’s looking at how the advances in sources are impacting biomedical applications more broadly.  That’s looking at advances in, for example, multi-modal imaging –  and looking at how relatively new sources like super continuum sources are being transitioned over into the application space.  And that’s a good example where there’s a need for those sources to be quieter and so that then flows back to the laser developers to really work on tailoring those sources for those kinds of applications.  I see biomedicine really being one of our significant growth areas in applications in technology in the coming years. 

 For more information on CLEO: 2013, visit www.cleoconference.org.

Apr 22

 

Top: Microplasma ignition in an argon-filled kagome-latticed hollow-core photonic crystal fiber. Bottom: scanning electron  micrograph of fiber facet, from B. Dabord et al, CLEO 2013  talk, CTu3K.6, "Microconfinement of microwave plasma in  photonic structures." Microplasmas show promise for  applications requiring small confinement of short-wavelength  visible or UV light such as photolithography or compact UV laser emission sources.

Top: Microplasma ignition in an argon-filled kagome-latticed hollow-core photonic crystal fiber. Bottom: scanning electron micrograph of fiber facet, from B. Dabord et al, CLEO 2013 talk, CTu3K.6, “Microconfinement of microwave plasma in photonic structures.” Microplasmas show promise for applications requiring small confinement of short-wavelength visible or UV light such as photolithography or compact UV laser emission sources.

This post originally appeared on Jim’s Cleo Blog and is reproduced with the author’s permission.

Microwave plasmas, optical vortices, gravitational wave detection, and mode-division multiplexing for high-capacity telecom systems are just some of the topics in CLEO Science and Innovations  11: Fiber, Fiber Amplifiers, Lasers and Devices. I recently had an opportunity to speak with subcommittee chair, Siddharth Ramachandran from Boston University, U.S.A. to discuss this year’s program on fundamental fiber technology and devices. Though at a surface glance we may think fiber and fiber applications to be very conventional or already “all-figured out”, Ramachandran noted the fact that this subcommittee continues to receive so many submissions year-after-year (in fact the second largest in the entire conference for 2013) indicates that this is still an extremely active area of fundamental and applied research.

Ramachandran said that contributed and invited talks for the subcommittee could be divided into to two main categories:  1) Novel Fiber, and 2) Fiber Applications.  The latter represents  breakthroughs in engineering, instrumentation, and devices from fiber technology introduced five to fifteen years ago. It is the product of well-tended ideas, hard work, and ingenuity coming into fruition. The former, on the other hand, will likely be the seeds for cutting-edge instruments and systems five to fifteen CLEOs from now. In terms of novel fiber work, Ramachandran discussed two trends 1) Kagome-lattice structures, and 2) Mode-division multiplexing for high-capacity communications.

“We are still developing all sorts of novel fibers. What a fiber is, in terms of being a high-index region that guides light surrounded by a low-index region, is not a settled issue. There are actually a lot of innovations going on.”

Ramachandran spoke of how a decade back, the excitement in fiber research centered around photonic band gap fiber (PBG) which guides light in air (or a structure of silica/air-cores), but still provides many of the properties of standard single-mode fiber, particularly confinement and guidance over many kilometers of length. “That was very exciting, and then what happened afterwards is people found out these band-gap effects are nice for guiding light but they tend to have very small spectral regions where they can guide light, so it is not as universal as our old fibers.”

Kagome-lattice fibers, named for the trihexagonal pattern of air-holes resembling the weave-pattern of a Japanese Kagome basket, may provide one solution to having the versatility of air-guided fibers, while allowing large-bandwidth propagation.

“What Kagome lattice fibers essentially do is solve this spectrum-limiting problem we had with photonic band-gap fibers. You can get huge bandwidth out of these, albeit with slightly higher (theoretical) losses. And so they have been very interesting for doing nonlinear optics of gasses filled in these fibers, to do all sorts of dispersive applications where you need crazy high-bandwidth, and for instance to create plasmas. And then there are people who are trying to make ignition torches with fibers which one would never have thought of doing maybe even five years ago,” said Ramachandran.

Vortex

Left: Spiral interference pattern of twelve distinct orbital angular momentum states (vortex modes) after propagating through 2 m of the air-core fiber shown on the right. Right: photo of the facet of the core shown on top and index profile on the bottom. From P. Gregg et al, CLEO 2013 talk CTu2K.2, “Stable Transmission of 12 OAM States in Air-Core fiber.” The potential for simultaneous propagation of so many modes shows promise for mode-division multiplexing for high capacity telecom systems.

 

 

 

 

 

 

 

 

 

 

 

 

The other category for submissions on novel fiber development on this subcommittee has centered on mode-division multiplexing for high-capacity telecom systems. Ramachandran discussed,

“The simplest way to scale information capacity might be to not just use a single mode in a fiber, but to start using multiple modes. And that brings with it a lot of complexities of how different modes interact with each other and what impact dispersion has? What does the area of the fiber do, etcetera, etcetera? Which cycles back to being a fiber design and fiber fabrication problem. So there is a lot of innovation going on there. Even figuring out what modes one wants to send. Are they the standard modes that we have seen in textbooks? Or are they these more exotic orbital angular momentum or vortex modes?”

In addition to contributed submissions in these areas, four of the invited talks concern novel fibers and their propagation effects. On the other hand, the remaining invited talks, tutorial, and contributed submissions focus on fiber applications. The tutorial, by Michael Marhic of Swansea University, U.K. entitled “Fiber Optical Parametric Amplifiers in Optical communications,” will be given on Thursday June 13, from 2:00-3:00 pm. The invited talks in fiber applications, which are indicative of the contributed submissions,  comprise topics as diverse as fiber parametric devices, microwave plasmas, gravitational wave detection, mid-IR sensing, and ultrafast laser combs.

LIGO

Top: Areal view of the Laser Intereferometer Gravitational-Wave Observatory (LIGO) at the Hanford Observatory site showing one of the 4 km arms. Photo from www.ligo.org image library. Bottom: One of the possible 3rd generation fiber-amplified laser sources for gravitational wave detection designed by Quest Centre for Quantum Engineering and Space-Time Research and Laser Zentrum Hannover e.V. Photo from Thomas Damm, Quest. Peter Wessels from Laser Zentrum Hannover e.V. will be describing many of the stringent requirements of laser sources used for gravitational wave detection such as high average power (~100 W to kW), single-frequency emission, ultra-low amplitude and phase noise, and diffraction-limited beam quality in CLEO 2013, invited talk, CW3M.5, “Single Frequency Laser Sources for Gravitational Wave detection.”

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ramachandran notes, “And the interesting thing about that space is the fiber itself that people are using is perhaps something that was developed anywhere between five years ago to maybe even fifteen years ago. We are now beginning to see all the promise that we initially thought that fibers could deliver and actually seeing applications across different disciplines of science and technology.”

Mar 11

A holy grail of photonics and electronics is the integration of silicon CMOS technology with electro-optical devices. In general, this is challenging because mature electro-optic components are made in compound semiconductors, such as GaAs and InP. Development of hybrid integration, where compound semiconductor photonics are combined with silicon electronics using material bonding techniques, is being pursued currently and is a promising approach. Another more direct method, however, is to try to make photonic devices from silicon directly. This is an appealing idea, since silicon is relatively cheap and the microelectronics industry has built up a large technology infrastructure around it.

However, the development of silicon photonic devices poses a number of challenges due to the material properties of silicon. For example, silicon is an indirect bandgap semiconductor, which essentially translates to it being a very inefficient photon emitter. Moreover, the silicon crystal is centrosymmetric (i.e., it has inversion symmetry, so points at (x, y, z) are indistinguishable from those at (-x, -y, -z)), which means it lacks the χ(2) nonlinearity that is responsible for the linear change in refractive index with an applied electric field. What do these two properties mean in practical terms? It takes a lot of ingenuity and hard work to realize two of the most essential electro-optical devices: the laser and the modulator.

Within the past several years, a few breakthroughs have helped develop these devices in silicon. A silicon laser has been created by using the fact that Raman amplification can occur in silicon. Raman amplification occurs as a result of stimulated Raman scattering. Raman scattering is a nonlinear effect that involves a pump photon generating a (typically) lower frequency photon and a phonon. The stimulated version of this effect is similar to that of familiar stimulated emission in lasers: the more signal photons in the material the more rapidly pump photons are converted into signal photons. Thus, amplification occurs, and with sufficient feedback one can make a laser. Although the performance is not at the level of conventional GaAs- or InP-based lasers, it is an encouraging and interesting first step.

A ring silicon laser based on stimulated Raman scattering nonlinear effects (H. Rong, Y. Kuo, S. Xu, A. Liu, R. Jones, M. Paniccia, O. Cohen, and O. Raday, “Monolithic integrated Raman silicon laser,” Opt. Express 14, 6705-6712 (2006).)

Silicon microring modulators based on the depletion effect (carrier-induced refractive index change) (A. Biberman, E. Timurdogan, W. Zortman, D. Trotter, and M. Watts, “Adiabatic microring modulators,” Opt. Express 20, 29223-29236 (2012).)

The challenge of making a silicon modulator has also been approached in creative ways. In many cases, since the linear electro-optic effect is not present in silicon, other refractive index altering methods are used. The most common approach is to utilize the property that adjusting the carrier concentration changes the refractive index. In this case, one can create a p-n junction and then modulate the reverse bias to change the depletion width, thereby changing the effective index of a mode traveling down a waveguide. This phenomenon has been combined with novel device structures, such as microrings, to make very compact, fast, and efficient silicon modulators. In addition, a more recent development has been to induce the χ(2) nonlinearity in silicon by introducing strain. In this case, strain changes the crystal structure such that the centrosymmetry is broken. Thus, a linear electro-optic effect is introduced, and refractive index changes can be induced by applying an electric field.

Schematic and SEM images of a strained Si modulator.
(B. Chmielak, M. Waldow, C. Matheisen, C. Ripperda, J. Bolten, T. Wahlbrink, M. Nagel, F. Merget, and H. Kurz, “Pockels effect based fully integrated, strained silicon electro-optic modulator,” Opt. Express 19, 17212-17219 (2011).)

These recent advances give some hope for developing photonic devices directly in silicon. Time will tell what the ultimate solution to bringing electronics and photonics together will be, but it is certain that the challenge has brought about some very ingenious and creative approaches.

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.

Feb 16

This post originally appeared on CLEO BLOG by Frank Kuo and is reproduced with permission from its author.

To probe new scientific frontiers, we need new technology. On the other hand, the advance of the technology relies on the solid scientific foundation. Countless examples have shown us that science and technology evolve together to give us wonders and a better understanding of the universe and nature. Looking back at 2012, similar stories happened in the laser and optics arena – Lasers are extending the working wavelengths into shorter (X-rays) and longer (THz) domain and probe new scientific frontiers. With this advance, we can have a better grasp of our nature.

Femtosecond X-ray free electron lasers, the most established source to generate “coherent (laser-like) X-ray”, relies on a gigantic synchrotron. In brief, a bunch of high-energy electrons from the synchrotron is sent into a long tunnel made of magnets. The tunnel, often more than 100 meters, is called undulator.  The magnets are arranged in a way such that they create an alternate magnetic field to wiggle the electrons and force them into emitting X-rays. The wiggles are tuned to the wavelength of the X- ray and creating a feedback mechanism – this radiated X-ray acts on the electrons, concentrating them into smaller and tighter groups, and makes the electrons emit more X-ray coherently. Apparently, it is very similar to normal lasing scheme, in which the radiation in the cavity induces more radiations. The main difference is that in the case of X-ray, there is no cavity since no reflective mirrors are available in this wavelength region.

What excites us in 2012 is that this “new light” gives us a better way to elucidate the secret of our living nature. It is used to probe the structure of the proteins: Continue reading »

Feb 10

Looking over the advance version of the CLEO 2013 conference program, I couldn’t help but notice an interesting trend in the “Semiconductor Lasers” invited speakers list: all of the topics cover what I’ve considered to be “unconventional” semiconductor lasers. Photonics crystals, diamond emitters, plasmonics, polariton lasers, and quantum cascade lasers typically don’t come to my mind when I think of semiconductor lasers. I sat back and contemplated this. Maybe these should pop into my head. After all, a consequence of scientific research is the continuous evolution of ideas and technologies. This might just be part of the new look of semiconductor lasers.

Conventional edge-emitter viewed from facet.
Conventional VCSEL viewed from side.

I probably should explain my perspective. Despite being exposed to and having even worked a bit with these “unconventional” lasers, my training has bred the perception that semiconductor laser is synonymous with diode laser; that is, semiconductor laser = active region (quantum wells) + p-n junction. The properties of the emitted light are determined primarily by the semiconductor material (band structure, which determines energy of the interband transition producing light, and such) and to some degree by the physical structure (well width, waveguide geometry, etc.). The wells could be inside a waveguide (an edge-emitter) or between distributed Bragg reflector stacks (a vertical-cavity surface-emitting laser). These are really the mature semiconductor diode laser paradigms that are found all over the place, in industry and science, and they have been (and continue to be) the topic of significant research for decades.However, simultaneously, there has been a movement to meld the attractive and unique aspects of semiconductors with novel phenomena. These include the aforementioned topics to be discussed by the CLEO invited speakers. Most of these are relatively new ideas that push the envelope of what semiconductor emitters can do. (Granted, it can be argued that quantum cascade lasers are fairly well established at this point, but they still break from the typical diode laser prototype since they rely on intersubband emission in a quantum well superstructure). And what all of these have in common is that they are approaches to move semiconductor photonics to regimes that were previously inaccessible (i.e. different wavelengths, smaller size, stronger light-matter interaction, etc.).

The tutorial subject illustrates what I consider to be a quintessential example of evolving semiconductor laser technology: photonic crystals. Susumu Noda, a professor at Kyoto University in Japan and expert on photonic crystal lasers, will conduct the tutorial. In a sense, photonic crystals are the ultimate manipulators of light, due to the flexibility of their design and the various photonic properties they can influence. Photonic crystals can alter light emission, propagation, and matter interaction (including absorption/gain, nonlinear effects, etc.). Combining the photonic manipulations enabled by photonic crystals with the light-matter interactions produced by semiconductors allows researchers to think about novel effects, such as thresholdless lasing and enhanced gain and absorption. It has helped create some serious thought about ultra-compact optical buffers, optical memory, and quantum photonic computing. Photonic crystals have definitely infused some new thought into the realm of semiconductor lasers.

Photonic crystal incorporated into semiconductor laser structure (Yoshitaka Kurosaka, Kazuyoshi Hirose, Akiyoshi Watanabe, Takahiro Sugiyama, Yong Liang, and Susumu Noda, “Effects of non-lasing band in two-dimensional photonic-crystal lasers clarified using omnidirectional band structure,” Opt. Express 20, 21773-21783 (2012)).

What defines a “semiconductor laser” is certainly evolving. As more is learned about what goes on at the nano-scale and in the quantum world, semiconductor lasers encompass more variety of physical structures and phenomena. And this potentially has been true for a while, but no longer can one simply consider the p-n diode with an active region when thinking of semiconductor lasers. Semiconductor lasers have been taking on some new looks, and with that, they’ve also added some remarkable new abilities. Stay tuned to CLEO 2013 for more.

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.

Jan 29

By Dominic Siriani

Diode lasers found their place in the world many years ago. Early on, they let us listen to our CDs and later watch our DVDs. They are in our little laser mice and our room-sized supercomputers. They are largely responsible for the telecom boom, putting the internet at our fingertips, and so help me reach all who read this blog. Like the transistor that preceded it, the diode laser has established itself as a cornerstone of modern technology. So this begs the question: what’s next?

 Well, the natural thing is to think bigger. I’m not saying make these lasers physically larger. One of them is smaller than a strand of hair from my head, and we like them that way. But the age-long question is how we can get even more out of these devices. How can we expand their sphere of influence to areas that require very high optical powers, while still maintaining their excellent efficiency and very small size?

Part of the answer has been known for a very long time, probably just about as long as the diode laser itself has existed: two lasers are better than one. By combining the emission from multiple diode lasers, you can still keep things pretty small and efficient but scale up to much higher powers.

 Until quite recently in the history of diode lasers, this strategy really wasn’t so essential. Advances in materials growth and processing, development of new device structures, and a variety of other ingenious ideas led to the gradual improvement of diode laser power and efficiency over time. We might now be in the midst of a change. I wouldn’t go so far as to say that we’ve gotten to where, like the microprocessor, we’ve hit a physical limit for conventional scaling methods. However, advancements have become challenging enough that it’s very helpful to utilize more weapons in the scaling arsenal.

DSo, the idea is pretty straightforward: gang together a bunch of diode lasers to get to your desired higher power. In practice, there’s some subtlety to it. For example, do you want to have a high quality beam or can you tolerate low beam quality? Do you need emission at a single wavelength, multiple wavelengths, or does it not matter? Diode laser beam combining methods exist for all these scenarios.

Consider, hypothetically, that you need to dump a whole bunch of optical power into a small area. Well, then you probably need good beam quality. But if you can tolerate (or even use) multiple wavelengths,then you can use a

Wavelength Beam

Illustration of wavelength beam combining (like running a diffraction grating in reverse).

technique known as wavelength beam combining, where, for example, lasers operating at regularly spaced frequencies are combined using a grating. Other techniques, like single-frequency phase-locking and incoherent beam combining, have their own sets of merits and application areas. These arrays really allow you to think of exciting niches for diode lasers: high-power solid-state laser pumping, laser welding, lidar, and the list goes on. And each one of these applications can require a different diode laser array type and beam combining technique. And, as one might imagine, there is not just one method to implement a particular technique. That’s great news: we’ve got all kinds of stuff to research!

This is a rather shallow overview of the importance, methods, applications, etc. of diode laser arrays and beam combining. And I really didn’t even touch on all the challenges! Luckily, there’s an entire symposium dedicated to high power diode laser arrays at the upcoming CLEO meeting. There you likely can learn more about the specific beam combining methods, where they’re useful, and what the state-of-the-art is. It’s an ever-evolving field, so it’s sure to be an exciting set of talks, pushing the envelope of what we can imagine diode lasers can do.

 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.

Dec 25

Demonstration of phase gradient microscopy in thick-tissue with back-illumination suitable for endoscopic integration. (a,c,e) amplitude images (b,d,f) phase gradient images of mouse intestinal epithelium. From T. ford, J. Chu, and J. Mertz, Nature Methods, 9, 1195 (2012). Jerome Mertz, Boston Univeristy, among other biomedical researchers, will be presenting latest breakthroughs in endoscopic imaging during invited talks at CLEO 2013 Applications and Technology: Biomedical.

This post originally appeared on Jim’s Cleo Blog and is reproduced with the author’s permission.

In the last two months, I gained a much larger appreciation for optical technology. Abdominal pain and pressure sent me to a number of doctors’ visits and a handful of endoscopic procedures: an upper-GI endoscopy, a colonoscopy, and a capsule endoscopy (the video camera in a pill). Before these, the most serious medical procedure  I had was a setting of a broken arm from a failed skateboarding trick when I was 11 years old. The stomach pain frightened me. It was deep inside where I couldn’t see it or get at it and it was making daily tasks and living difficult. I was so relieved to be prescribed the first endoscopy and then the followup procedures. It gave me an element of control. The thought repeatedly running through my head before and after these procedures was, “how fortunate I am to live in the time I am in.”  The upper-GI procedure took  less than 15 minutes, was painless, and I found out immediately after that my esophagus and stomach looked healthy. Tests from biopsies less than a week later confirmed this was true. I had similar experiences with the other endoscopies. I was given amazing information about by internal organs in fairly non-invasive short outpatient visits. The figure below shows one of the video frames of my stomach.

Stomach tissue from my own recent upper-GI endoscopy using a conventional commercial endocscope.

Because my own work in ultrafast laser systems has applications in nonlinear endoscopic imaging, I have used the words “optical biopsy”  (the idea that tissue is cleverly analyzed with photons during the procedure instead of “barbarically” exised to be sent to a lab and analyzed later) and “non-invasive” in introductions to papers, talks, or in explanations to lab visitors how an ultrafast laser has relevance to the average person. In the promotion of ultrafast lasers for optical biopsy, I  have sometimes talked about how the time and effort it takes to run biopsied tissue through histology is long and arduous-it needs to be sliced thin and stained in order to be viewed with a conventional microscope, and then analyzed by an expert. The patient distressingly waits for a diagnosis and also pays a non-trivial sum of money for the professional time involved for analysis.

I couldn’t have imagined the importance of these motivations before my own endoscopic procedures. What was part of my ultrafast laser stump speech was suddenly very real and worthy. My own experiences were definitely non-invasive. What would have been my options when endoscopes were larger and bulkier? What would have been my options prior to widespread use of endoscopic diagnosis?  And though my waiting for histology was short, it was still difficult and definitely costly. What advantages will the next generations have as optical researchers and engineers push endoscopes to use more imaging modalities? Push them to smaller sizes and with more functionality? What peace of mind can we pass on?

No doubt many contributed talks to CLEO 2013 and postdeadline papers will address advances in endoscopic procedures, endoscopes, and catheter-based probes. Last year’s postdeadline session saw two papers on endoscopic imaging: one from a collaboration between John Hopkins Univeristy and Corning, Inc. led by Xingde Li for efficient, high-resolution nonlinear endomicroscopy and  the other from Chris Xu’s lab of Cornell University which piggy-backed wide-field one-photon imaging with high-resloution two-photon imaging in the same device for optical zoom capability.  There were also a number of contributed submissions regarding advances in endoscopy such as the work by Adela Ben-Yakar’s group of the University of Texas at Austin whose endoscope used the same ultrafast laser for two-photon imaging for targeting tissue and subsurface precision microsurgery  through athermal ablation. Last year’s CLEO also hosted an invited talk by Brett Bouma, pioneer of Optical Coherence Tomography (OCT), on translating OCT into GI endoscopy.

This year’s invited speakers in CLEOs Applications and Technology: Biomedical will also be addressing future directions on endoscopes and  endoscopic procedures. Invited speaker Jerome Mertz of Boston University will be discussing his work on phase contrast endomicroscopy which was just published in this week’s  Nature Methods. His technique cleverly uses two diametrically opposed off-axis sources to allow oblique back-illumination  in a reflection mode geometry. Traditionally phase contrast microscopy using oblique illumination requires transillumination and is therefore not suitable for in vivo imaging. Mertz’s back-illumination technique allows his microscope to be miniaturized and integrated into an endoscope for which the source and detection optics must reside on the same side of the sample. Unlike traditional oblique illumination phase contrast, Mertz’s technique can be used to image thick samples.

Continue reading »

Oct 22

This post originally appeared on CLEO BLOG by Frank Kuo and is reproduced with permission from its author.

It is an understatement when we describe nature as the most talented painter. In fact, she is not only the greatest artist, but also the most renowned scientist, in essentially all aspects. Her scientific achievements are found everywhere. For example, today, much of our knowledge in the field of bio-photonics is just a re-discovery of what she has done (Another interesting topic which relates the evolution to optical science can be found here).

Many of the astonishing color patterns we found in the insect kingdoms are manifestations of nanometre-scale architectures. These architectures are collaborative works of cells. Those cells cooperate together to create optical effects we widely apply in modern photonic science. For instance, butterflies have cells structures that look like multi-layer reflective coatings on their wings. Depending on the thickness of each layer, different colors present vividly. Same tricks have been adopted and perfected by many shiny beetles. As shown in figure 1, enchanting colors on the surface of the insects are precisely the magic of multilayer structures. The layers are mostly composed of thin parallel sheets of chitin (secreted by the epidermis and often interspersed with other organic components). These layers differ in refractive index. And again, depending on the spacing between these layers and their indices of refractions, different colors can be reflected. Furthermore, some insects have arrays of very fine elements, known as nipple arrays, which look like micro lenses with subtle variation of index of refraction, to reduce reflectivity in their compound eyes and enhance collecting the light from the environment. Nature did create optical science way before mankind stole fire from Prometheus!

Figure 1. (a) A presentation of simple cuticular multilayer reflector. (b) The cross section of a cuticular reflector. (c) A colorful buprestid. (d)-(f) Different structures of cuticular multilayer reflectors commonly seen in insects. Courtesy of A. E. Seago, P. Brady, J-P. Vignerson, and T. D. Schultz in J. R. Soc. Interface 6(supp2) S165–S184 (2008).

Continue reading »

Aug 16

Many of us have heard the popular expression “curiosity killed the cat.” The saying is used to warn of the dangers of unnecessary investigation or experimentation. However, less widely known is the rest of the phrase. In full, it reads “curiosity killed the cat, but satisfaction brought it back.”

The full saying recalls the significance of a curious mind. Indeed, curiosity has been listed as an important trait of genius and an examination of many of the intellectual giants of the past, such as Albert Einstein, Thomas Edison, and Leonardo DaVinci, reveal that common among these great minds is the curious nature of their character. In fact, it was Albert Einstein that said,” I have no special talent. I am only passionately curious.”

Curiously (pun intended) a Great Britain report on the common characteristics of physicists published in 1993 by a group of scientists assigned a host of adjectives to the profession, but curiosity was not listed as one. However, it is hard to imagine that individuals who gravitate to physics are not driven by their curious nature. I need only look to my father, who obtained his doctoral degree in physics, as a case study on the topic. My father was possessed with constant curiosity, which resulted in use of his spare time to continue his probing quest for knowledge. Often, after working a full day, my father would, for curiosity sake, prepare and solve formulas in his basement office and devour cover to cover every issue of Physics Today. While my father knew attempts to share his curiosity for physics would fall flat on his daughters, he made sure to impart on his girls their need to cultivate an inquiring mind by exploring the world and what it has to offer. True to his nature, family trips were made lengthy by a desire to ensure that we stopped at every historical landmark whether on the path or not to our destination.

My present position has me mingling with scientists like my father on a regular basis at scientific conferences. In my interaction with these individuals I find their personal characteristics to widely differ. That being said what shines through is the healthy curiosity that our conference participants bring with them to CLEO programs and the like.

My next conference of this type has me in San Jose, CA where along with the hundreds of impressive speakers on tap to discuss the latest research in optics and laser science, there will also be lots of attractions to explore in sunny San Jose, CA. I hope attendees take advantage of that curious nature to not only enjoy pioneering research but also the host of available attractions in the area and nearby San Francisco.

May 14

This post originally appeared on Jim’s CLEO Blog and is reproduced with permission from the author.

Flying back home from San Jose I couldn’t help wonder with excitement if our field is on the verge of a “transistor moment.” Maybe it was just my CLEO conference euphoria coupled with high-end caffeine from Cafe Frascati still in my system. However, I feel like something big is going to happen, particularly in the field of photonic circuits and nanophotonics.

The explosion of work in this subarea is impressive and CLEO hosted a number of talks from the leaders and pioneers in this field. You can still watch a handful of these on the CLEO On Demand video  such as Yurii Valsov’s plenary talk on fundamentals and applications of silicon nanophotonics, Larry Coldren’s tutorial, CWK1.1, on single-chip transmitters and receivers, and Dave Welch’s tutorial, JM4.I.1 on semiconductor photonic integrated circuits, just to name a few. Cutting edge science is interfacing with better fabrication processes- repeatability and low cost. At the poster session on Wednesday night it seemed every group was using some kind of micro ring resonator. Simple photonic circuits are becoming standard. Will our children have the nanophotonic equivalent of a Heathkit radio- something like “My first Fab.” It seems a sure thing to me that my daughters will be using optical/electrical hybrid computers in their lifetime. And it seems even more certain to me that nanophotonics is the future of our field.

However, will something even bigger, more profound, and unexpected happen like when Walter Brattain dumped his amplifier experiment in a thermos of water in 1947 to successfully demonstrate electrical gain of what was to become the transistor? The same little amplifier that gave birth to a small startup company named Sony and then later to Texas Instrument, Intel and the entire business of integrated circuits and computation as we know it. The transistor was at first a “mere” amplifier. Later it became the foundation for all computer logic and a new era of technology. I wonder what is within our grasp that we don’t realize.

Yurii Vlasov used imagery from the Wizard of Oz in his plenary talk of a road to follow to the Emerald City (our goals of nanophotonics and computation and the windy road we will take). However, I wonder what ruby slippers we are wearing right now. What  ”transistor potential” is waiting to be unlocked. It’s a good time to be in the field of photonics. We will be the leaders of the new information age and the technology that drives and supports it.

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