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Tuesday, May 10, 2011

CLEO/Europe EQEC 2011 is ready to relay the success of CLEO US.

Just like the movie slogan, “everything that has a beginning has an end” (I should reverse this to make it more suitable for this short blog). Everything that has a terrific end has a new exciting beginning. Indeed, something electrifying is happening across the Atlantic. Every two year, CLEO/Europe EQEC 2011 (22-26 May, Germany) is taking the heat to Europe and once again is looking forward to resonating what we have just completed in CLEO.

For people like me, who doesn’t have the luxurious time and funding to enjoy another wonderful trip, you can easily find the detailed programs in this link. Once you click the link and scrutinize the abstracts, I hope you don’t get trapped. For sure, the conference is loaded with crazy and smart ideas. Here are just some I found:

EE1.5 SUN 10:00 “The Size of the Proton” -- This rings the bell in my brain. I read about this in Scientific America a few months ago, and that sticks to my mind. On the one hand, I simply have no idea how laser spectroscopy can be used to measure the radius of the proton. There must be some original way, to me, a proton is almost dimensionless. On the other hand, they give a more precise but exotic value of it. Would this value forces the theoretical particle physicists to re-think what they have formulated for the past decades?

JSII1,2: “Low Dimensional Carbon Nano-Structures in Photonics I, II” -- Apparently, the Nobel prize simply marks the beginning explosion of the graphene related research. We are familiar with the novel material features of graphene and nanotubes. In addition to investigate their physical properties using lasers, how about using them to mode-lock a laser? Or using double wall carbon nanotubes to create broadband ultrafast pulses? Sit in these presentations, and you will find out.

CL/EB1-3 “Medical Imaging, Advanced Microscopy, Advanced Biophotonics: Sensing and Imaging” -- This is where you find yourself accessing the fresh. For people who are fond of applications, these are the harbors. It is simply a zoo of creative methodologies. I like the techniques that play around with the light polarizations. You might enjoy using nanoparticles to be the bio-markers. Just explore them and make your own list of preference.

OK, Time for you to take this journey to Germany, either physically or virtually. The destination is the same for all of us. Remember to check out the plenary sessions -- from attosecond lights, and insights of the cold atoms/molecules, to the advances of solid-state lasers. Feels like another feast to me. Finally, don’t get me wrong, almost everything that discussed in CLEO, you can find the continuation of them in CLEO/Europe EQEC 2011. I will leave you to connect the dots. Cheers!

DISCLAIMER
The opinions expressed herein are those of the author and do not represent the Optical Society of America (OSA) or any OSA affiliate.

Friday, May 6, 2011

Fully Charged, will be back for more next year!

Just want to touch a few more fields before we wrap up this amazing CLEO 2011. The truth is, we all learn a lot and we will crave for more soon.

I guess we are by now all familiar with the metamaterials thanks to the powerful broadcasting media and online news. Metamaterials have some complex indices of refractions, which bend the light in a whole new way. Even nature utilizes it. The amazing colors on the butterflies, insects, are all originated from the nanostructures – some variations of metamaterials. However, I realized yesterday, this is OLD news.

Researchers now have something new called (well, new to me) “configurable metamaterials”. Unlike before, a specific metameterial is only suitable for one frequency; nowadays we can tune the properties of them by varying the temperature, through optical pumping, and more. If we use some materials that have strong thermal or optical responses to construct the metamaterials, these phoeneoma can be achieved. The concept seems to be there for quite a while, but it is just thrilling to see the real works have been done.

This morning, Dr. John E. Bowers gave an amazing talk on silicon photonics. I feel like soon in the future, silicon will replace the metallic wires in the computer, become the light source of miniature sizes penetrating to our daily lives, and constitute the cores of our gadgets. Furthermore, the data transmission rate is much higher (with tens of GBs per second, more than enough to watch all channels of HDTV at once), and the heat generation is negligible compared with the computers of modern days.

Make sure you check the article in photonics spectra and this one in from Intel to peek the future. Think about it, if we have the silicon-based waveguide/lasers of tiny dimensions, combined with flexible LED panels, we can make the electronics so small and life will totally be awesome.

In addition to using silicon as data transmission media, a hybrid silicon ring laser, like the three shown here, could be used as an on-chip light source in future photonic circuits. The rings are just 12.5 µm in radius and consist of III-V compound semiconductors. Waveguides – the black lines running below the rings – traffic the light back and forth. (Courtesy of Di Liang, University of California, Santa Barbara).
Fiber lasers/amplifiers have drawn huge amount of attention in the past decade. The Holy Grail is to replace the free space lasers in many applications. If they succeed in doing so, I would imagine all the laser-based medical devices would use fiber lasers since they can be made compact, robust, and essentially free of aligning. They can even revolutionize the optomechanics’ market (apparently, a lot of free space optomechanics will be forced to retire). Like past few years, great advancement/or continuous improvement are seen in this conference, such as mode-locked fiber lasers, fiber amplifiers, fiber parametric devices, new wavelength fiber lasers, beam combining and stabilization of fiber amplifiers, and even fiber based sensors (browse your brochure one more time if you are too busy to notice these).

Advances in biological microscopy and nanophotonic sensors once again carry the light applications into another degrees of freedoms. There are numerous ways of doing microscopy, old and new, classical and bizarre. Some promise more while the other create intellectual and instrumental challenges. Each category of them suggests a new direction for laser manufacturing. I guess this is part of the fun in research pioneering! On the other hand, advances in nonophotonic sensors do make me realize we have to re-think the limitation of “instrumental sizes” almost every time you think about it. Indeed, researchers give you a new definition of instrumental size almost every year!

See you all in next CLEO or actually next conference!


DISCLAIMER
The opinions expressed herein are those of the author and do not represent the Optical Society of America (OSA) or any OSA affiliate.

Thursday, May 5, 2011

Applaud with appreciation to all the poster session’s presenters!!!

Attending poster sessions is energetic and adventurous. It is even a great social event. Compared to technical session, you never fall asleep and you can interrupt the presenters whenever you want (How great is this, you simply have a personal tutor at your disposal). In additions, you learn more in less time if your mind is a knowledge sponge.

Forgive me for sampling only today’s poster session. Actually I totally regret I didn’t spend enough time in the last few days for poster sessions. To me, these successfully poster sessions really mark one of the highlights in CLEO 2011. Here are some of them that I got a chance to interrogate the presenters (they were just busy, it was quite hard to squeeze in to ask even one question):

JThB8, Generation of a macroscopic singlet state in an atomic ensemble – I learned from this poster that you can create a spin 0 ensemble using weak optical pump coupled with active feedback. In other words, you start from cold atoms and squeeze the distribution of the spins in a way that it approaches zero expectation values in all directions through a tailored Hamiltonian. Quite amazing, but it has been realized beautifully by the researchers.

JThB25, Twin-photon correlated confocal microscopy – the lateral resolution of the microscopy is defined by the diffraction limit. A clever way to improve the resolution for more than 60% is proposed and performed by utilizing a phase plate right in front of the sample. In a nutshell, the phase plate encodes different phases for the points that are not in the vicinity on the sample. If the points on the sample were more separated, the imposed phase would be more different. A smart detection scheme then only picks up the signals that have no phase difference. By doing so, the light from one point on the sample is amplified and that from points nearby are suppressed. This greatly enhances the lateral resolution.

JThB28, Photon-phonon entanglement in a coupled optomechanical system – the entanglement of photon and phonon is studied thoroughly in this simulation work. A system with two coupled optomechanical cavities is the model system (imagining one side of the cavity is on a spring, so this cavity supports phonon modes). Two cavities are coupled by cavity-supported light modes. It is found that the light can couple the photon modes to the phonon modes of the cavity. And this entanglement lasts more than 500 seconds. This really blows my mind away; I used to think the entanglement doesn’t sustain itself for this long.

JThB42, Conical interaction dynamics in a rhodopsin analog: isorhodopsin – Ultrashort pulses (~ 10 fs) from NOPA are used to investigate the isomerization of rhodopsin (the first chemical reaction in the mechanism of “seeing things”) and isorhodopsin. By compared with the results of isorhodopsin, it is found that the isomerization of the rhodopsin molecule is actually optimized on the right chemical bond location. As a result, the efficiency is superb. Nature does her job, indeed!

JThB45, Unidirectional perfect transmission resonances in nonlinear asymmetric photonic multilayer – Combining theory and experiment, a photonic crystal multilayer, which transmits light in one direction but not the other, is realized. In one direction, the transmittance is more than 92% (the reverse direction, the transmittance is less than 20%). This is actually a one-way photonic crystal and I think applications based on this will come in the near future. The presenter is so nice and gives me some advice on the technical session -- His way of arranging the chairs will definitely increase the seating capacity by at least 2-fold. Your opinion is greatly appreciated.

JThB137, A comparative study of Raman enhancement in capillaries – OK, I have to admit, I love this one. The experiment is straightforward but so smart and neat. The laser light is guided through a hollow photonic crystal fiber by a high NA objective. The hollow fiber is filled with the solution of the chemicals. The light has very high photon density in the fiber and the interaction length of the chemicals with the light in the fiber is long. Subsequently, the Raman signal is found to increase by ~ 10-fold. 10-fold is an astronomical number to me actually, but the result confirmed this nicely done work.

Thanks again to all the poster session presenters! Bravo!!!

p.s: Just realize there is a Light Street right beside Baltimore convention center. Maybe that is why we have CLEO 2011 here!?

Light Street, Baltimore, MA!!!
DISCLAIMER
The opinions expressed herein are those of the author and do not represent the Optical Society of America (OSA) or any OSA affiliate.

Wednesday, May 4, 2011

When light dances with sound, teases the molecules, and plays an important role in green energy!

Shuffling among many eye-opening technical sessions and CLEO’s Market Focus & Technology Transfer Showcase, I simply realize adventures with light are everywhere:

An amazing imaging technique called photoacoustic imaging/microscopy (JTuG) caught my full attention on Tuesday. It is a perfect example of light collaborating with sound to achieve something fascinating.  Think about it, light and sound are siblings. They are governed by similar natural laws. You might argue that light can propagate in vacuum while the sound needs media to do so. But again, they are siblings, not twins. So this argument does not really hold. Anyway, taking that into account, isn’t it fun to see them hold hands and work on something new together!?

The principle behind this new imaging technique is actually straightforward. The pulsed laser light (MHz repetition rates) is focused into the tissue; the tissue of interest absorbs the light and expands. This process is repeated with laser repetition rate. The pulsed expansion creates the ultrasonic sound wave, and we detect this by transducers. We then reconstruct the image of the tissue through some complex algorithm. We know that ultrasonic can penetrate deep tissue, while the resolution of ultrasonic is not as great as optical imaging. On the other hand, optical imaging can only go to a few millimeters deep. By endeavors of the researchers in improving this technique, photoacoustic imaging actually combines the strength of these two – it can do deep tissue imaging with optical imaging resolution – optical resolution photoacoustic microscopy.

An experimental layout for photoacoustic microscopy.
Fast-forward to Wednesday, a wonderful QELS session (QWB) focusing on laser cooling and its further applications on quantum computations and simulations are really hardcore stuffs. Using light to produce ultra cold molecules is definitely pushing the frontiers of science. We all heard of atoms cooled by lasers and a Nobel Prize was given to this achievement. But for molecules, things are more difficult. They have inertial structures and as a result, complicated processes are involved when cooling them by laser light. However, diatomic molecules are being cooled to sub micro Kevin through Sisyphus and Doppler cooling (check this article for more). If you missed today’s presentations, it is totally ok. On Thursday, sessions like QThJ, QThM, QThN, and QThO will feed your quantum hunger.

Talking about green energy, Laser Inertial Fusion Energy (LIFE) is discussed during CLEO’s Market Focus. Due to human mankind’s need in energy, we turn to fusion, and we intend to do so by using extremely high power lasers. LIFE utilizes 384 powerful lasers to create pulses with the energy of 3.1 mega Joule in IR and 2.2 mega Joule in UV per pulse. Each laser has the size of a truck and can be swapped in and out as a unit if the lifetime is reached or malfunction is found. This kind of gigantic project requires the state-of-art techniques and actually drives the development of the optical industry, such as glass productions. If you dig even further, the diode pumped helium cooled mercury amplifier inside each laser is just breathtaking. The helium is blown through the gain media with 0.1 Mach speed to cool down the laser. In other words, you even need aerospace technology to prevent the turbulence inside the laser.

Finally, also thanks to CLEO’s Market Focus & Technology Transfer Showcase, I just learned that an animated website created by JDSU called Photovoltaic for generating and measuring energy is a good starting point to know how light plays the role in green energy. Enjoy it and do not forget to check out CLEO’s Technology Transfer Showcase program tomorrow.


DISCLAIMER
The opinions expressed herein are those of the author and do not represent the Optical Society of America (OSA) or any OSA affiliate.

Tuesday, May 3, 2011

Behind every successful conference!!!

An exciting conference is mainly composed of two parts – technical sessions and exhibition. We enjoy the technical sessions because that’s where we learn from our peers, get our brainstorms, and have a quick update on the scientific frontiers. These are addicted as you can tell me about it. However, ask yourself about the definition of a successful conference. Most of us will say a conference will not be complete without stopping by the exhibition hall to see the zoo of new products and technologies presented by numerous companies. Well, the souvenirs we gather from each booth are attractive too!


If we take a step back, we realize that convention center is a very busy host. Every week it is embracing a new show and new people with crazy ideas. This makes me wonder, what kind of preparation is required to host a welcoming conference? For technical sessions, things are easier to picture since most people had the opportunity to observe or organize a symposium either in the school or in a research institute. We need to multiply everything by at least a hundred. These are OK, we can have more rooms, chairs, projectors, laser pointers, and most importantly, more coffee and labor. So we can make this happen. Now, if we think about the preparation of an exhibition hall, a blank image usually emerges. I did not even know how an exhibition hall looks like before all the companies fight for the space and start to build their own territories, not even mention about how to set it up. Thanks to my job duty and helps from the colleagues, now I have observed the way it happens…^_^


The convention center is moving at a very fast pace as we mentioned. The first thing we have to realize is the time you have to build a booth. Normally, each company has a full day working with the labor of the union to set up everything. In other words, people are working under great pressure. The very first scene I saw is that everyone on the floor was tense since all they faced is a concrete floor marked by chalk to specify the territories of each company. Phones were ringing all the time because on the other side of the exhibition hall, hundreds of trucks were waiting to ship the equipments into the hall. In the meanwhile, experienced workers maneuvered loaded carts, and crates were shuffling among people. These would go on for several hours, and step by step, each big and small cargo reached the right destination, while small hassle was happening all over the place (such as some trucks got lost, according to the workers, this is quite normal).



Small carts moving around the cargos and magically they all arrive at the right destinations.
After this was all set, locating the power jackets and building tiny power grids on the floor were next. We can fairly say, without the electricity, the exhibition hall would be like a haunting house rather than a technology showcase. But for the beauty of the exhibition, we want to hide these power grids. So we make them lying comfortably on the floor and covered by carpet later on. By doing so, we will never spot them unless you come to the hall before the grand opening. At the same time, small hydraulic trucks were busy putting the overhead canvas slogans and signs above company’s booth. From this moment on, we would not get lost, since the flag (well, the slogan) was waving on each and every corner of the hall.


The power grids (shown in orange) on the floor are taped down nicely and distributed very efficiently for the booth use. 
Time to do some makeup. The “base foundation” was the carpet. It covers all the power grids and jackets, all the chalk signs, and marks the lanes of the traffic. Putting the carpet represents an important step – “the equipments are ready to get some fresh air.” Knowledgeable technicians started to open the crates (always with complaining, since equipments had legs, they moved around after staying in the trucks for so long), tried to do preliminary assembling, and finalized the floor plans. They spent another several hours to put optical tables together, made the equipments up and running, and arranged and cleaned the surfaces of each components. These are tedious work, and work was again under great pressure.


This booth is about 50% done. Technicians have been working for hours, and there are still al of of crates need to be opened and arranged on the optical tables.
Just like LEGO we played when we were young, setting up the booth was like intense LEGO works, except they are much bigger and you cannot quit if you feel tired. It is not uncommon to see people work way beyond midnight because they want to present the best to the researchers and the students the following day. After technicians and the product line managers were satisfied with the setups, final cleanup was required. Final vacuuming on the floor, tearing open the plastic wrapping of the carpet, and covering the equipments and tables with blanket were essential works not to be omitted.  Everyone wanted to keep every link neat and flawless.


After a detailed inspection on the booth, we can call it a day. Hmmm, time for bed or time for a drink?! I would like to thank Mr. Hoang Hung and John Carter, the men who are in charge of the booth setup. Without his help and explanation on the details, I will not be able to peek through this new window to see how to dress the conference!


Another successful show!!! After seeing so much traffic, all the efforts and sweats are just sweet!
DISCLAIMER
The opinions expressed herein are those of the author and do not represent the Optical Society of America (OSA) or any OSA affiliate.

Monday, May 2, 2011

From the smallest lasers to the biggest ones!!!

With so many different kinds of lasers play essential roles in modern researches and daily life, it is tempting to find out what are the extremes among them. Thanks to this conference, this question intrigues me once again during a talk (QMF3) where a gigantic free electron laser (FEL) was mentioned and used to probe the atomic structures. Searching with the conference program brochure and within my memory, here is what I can find.

The winners of “the biggest” prize go to the FELs. Taking the one in the U.S. soil as an example, a FEL powered by a two-mile-long linear accelerator (linac) in Stanford Linear Acceleration Center (SLAC) has a grand name associated with it  -- Linac Coherent Light Source (LCLS). Technically speaking, it is a laser of more than two miles in length and many many tons in weight (I don’t think people actually weight this monster, figure 1). Basically, after SLAC’s linac accelerates very short pulses of electrons to 99.9999999 percent of the speed of light; the LCLS takes them through a 100-meter stretch of alternating magnets that force the electrons to undulate back and forth. This motion causes the electrons to emit X-rays. Since the electron motion is in phase with the field of the light already emitted, the fields add together coherently.  As many as 10 trillion X-ray photons can be produced and squeezed into a bunch that’s a mere 100 femtoseconds long. This giant laser has a sibling across the Atlantic. In Europe, an x-ray free electron laser (European XFEL) shared by 14 countries is powered by a 2.1 km long superconducting linear accelerator.

Figure 1. The aerial view of the monster FEL laser in SLAC.
The runner-up would be FELs powered by the synchrotrons. Although there are huge ones such as LHC, the ones that are used to pump FELs are smaller, such as Japan’s SPring-8 and France’s SOLEIL (on Wednesday, a presentation (CWG5) utilizing this instrument will be discussed). Well, maybe Synchrotron has a bigger surface area than linear accelerator, since I am naming the prizes, let’s say, the length is what we compare.

Just a bit digression, an instrument (or experiment) involved 192 high power lasers is an unusual contender for this prize. Apparently, researchers in Lawrence Livermore National Laboratory’s (LLNL) National Ignition Facility (NIF) are trying to fulfill the dream of fusion by focusing many lasers in a capsule of size equivalent to a peanut. By squeezing so much energy in so little space (with the existence of hydrogen), they are optimistic about that the fusion is bound to happen.

Let’s swing to the other extreme. Nano-lasers with many different designs can proclaim the winners of the “smallest” prizes. A quantum cascade laser embedded in a microcavity and emitting THz radiation is one of the smallest lasers available (with a size of a few tens of microns). But the 44-nanometer "spaser – surface plasmon laser" will be very hard to beat. The device is a hybrid -- A bluish-green laser beam is shined into a suspension of gold nanoparticles.  A layer of sodium silicate and an outer silica shell containing dye molecules surrounds each of these particles. When the gold is excited by the laser photons, collective oscillations of electrons on the surface, known as surface plasmons, are excited. The plasmons then excite the dye molecules, and subsequently the photons released from the dyes stimulate more plasmons on the gold at the same wavelength, causing the device to emit green laser light. How amazing is that!


DISCLAIMER
The opinions expressed herein are those of the author and do not represent the Optical Society of America (OSA) or any OSA affiliate.

Sunday, May 1, 2011

CLEO/Laser Focus World Innovation Award endorses the recent triumph of Terahertz (THz) spectroscopy and applications.

This year, the award goes to Applied Research and Photonics Inc. for its endeavor in THz device and applications. This is indeed another sign saying that THz will be a hot topic for the following few years thanks to many people’s efforts over the past two decades. Besides, we are very happy to see this field has grown into a vibrant society with its own conference – Optical THz Spectroscopy and Technology (OTST). I was there, learned many news things from researchers all over the world, and enjoyed the nice breeze from the Pacific sea in Santa Barbara.

Thinking about THz, most of us immediately connect it with a couple of concepts, including the wavelength of it is long compared with the familiar optical and even mid-IR wavelength (a wavelength of 1 micron is 300 THz while 1 THz is 300 um), the property of great penetration to soft materials like tissues, plastics and, card boards, and its application in security screening due to the sensitivity of many explosives. In addition, its low energy and non-invasive feature is perfect for authenticity test on artwork and biomedical imaging. With this field burgeoning like never before, it is worth to take a quick look on the methodologies of generating THz.

The most orthodox way to create THz laser is to find a suitable gain media and pumping source. Just like a dye laser in which an electronic transition of dye is directly related to the lasing frequency, the transitions between the rotational states of methanol gas falls right into the THz region. A very good white paper using methanol and pumped by a CO2 laser can be found in here. Of course, the gain media is not restricted to methanol; even water vapor is actually a good THz source.

Mixing two lasers with the frequency difference in the THz regime is another neat way. Considering mixing two lasers in the optical fiber, the beating that is produced by the frequency difference of these two lasers is just the source of the THz. If we can filter out the pumping lasers, then we have a useful THz radiation. A more efficient way of doing so will be mixing two lasers in the nonlinear crystals (GaAs, LiNbO3, … etc). Depending on the nonlinearity of the crystal, frequency conversion is achieved with different efficiencies. In this case, the efficiency of THz generation is proportional to how strong the nonlinearity of the crystal is. This principle is adopted by Applied Research and Photonics Inc. to the extreme. The core of its THz device is based on a polymeric nanomaterial that has very strong nonlinearity.

How about generating ultrashort THz pulses to cover a wide THz spectrum at once. A very exciting way of doing so is through air plasma. The principle is quite straightforward although there are several variations of it (figure 1).  Basically, you create air plasma in the air (by focusing intense laser pulses in air), drift the electrons away from the nuclei through different bias methods, and then the nature law takes over. Since the electrons will recombine with the nuclei through coulombic force, this process creates a transient current (or a oscillatory dipole). An oscillatory dipole/transient current in this process creates radiation that covers THz regime. Before the advance of intense lasers, researchers focus laser beams onto photoconductive antenna chips to create transient current. Actually this is still the most popular way to generate ultrashort THz pulses.

Figure 1. THz generation based on air plasma. In all scenario, air plasma is generated by intense laser pulse (red). Electrons are accelerated in the direction of laser pulse . This process creates THz in a cone fashion.  Electrons are drifted away by external DC source (b), by another laser pulse (c), and by the laser pulse itself (d). Courtesy of Thomson M., Kreb M., Loffler T., and Roskos H. in Laser & Photon Rev. 1. No. 4. 349 (2007).

Just a reminder, on Monday, CLEO has an entire session focusing on TH Sources. Besides, the award presentation will be during the Plenary Session in the same day evening. This is definitely another power boost for you to learn how it goes in this field. Hopefully, next time when we encounter THz research, we all know a bit more in their business. You can also explore THz quantum-cascade lasers, THz generation by pulse front tilting in the crystal, and more through the power of the Internet…^_^.


DISCLAIMER
The opinions expressed herein are those of the author and do not represent the Optical Society of America (OSA) or any OSA affiliate.