Espresso for the Brain – CLEO: 2013

Being an active OSA young professional comes with additional bonuses once in a while. This time, I was happily summoned as “scientific paparazzi” to sneak into one of the committee meetings for CLEO: 2013 happening in the DC metropolitan area. Digging for insider info on CLEO’s hot topics and from CLEO: 2013 committee chairs and members – as they reviewed, scored and sessioned all the CLEO papers was the top mission.

 

My first impression about this conference is the vibrant energy. All the chairs and committee members were holding such high spirits. I don’t feel they came to the conference as referees to select the best papers. I feel they came to learn more and look for new inspiration. While it can be difficult to make decisions on which papers represent the best in the field – they are there to do their job – accepting only the highest-quality papers for the CLEO: 2013 program.

 

My first personal encounter with one of the Chairs was a short conversation with professor James C. Wyant, who also served as President of OSA in 2010. As program co-chair of “CLEO: Applications & Technology,” he is very happy to see CLEO is creating a trend of applying its strength in core science into applications. This, of course, will foster more interaction between academia and industry. He is especially keen on the topics about “metrology” and “sustainable energy – laser-driven inertial fusion energy”. If you are still not aware of these two topics, I strongly advise you to check out the short course on metrology, and the tour of the National Ignition Facility (NIF) to learn more and gain a first hand experience. All of these sound very exciting. Joining the tour allows you to have the chance to see one of the most powerful lasers in the world, and how to use it to mimic the core of the sun. And, the metrology course will introduce you to the tabletop X-ray light source that is one of the prominent rising stars in optical science. You better grab your opportunity to attend by checking out the CLEO website now.

 

Professor Wyant also shared the concern about the impact of U.S. federal government’s sequester on optical science too. Although we all feel sorry about the cuts on financial support, he is cautiously optimistic. Optical science has found its applications in many aspects of our society, and many more will come. With all of humanity benefiting from optical science applications, we shall look for more that originate from optical science to accompany our future. Thanks to him and many other researchers, we are striving toward this goal.

 

Then, I was lucky to catch a few humorous and witty scientists during the lunch break. Having a meal together with Professor Christian Wetzel, Professor Mark A. Zondlo, and Dr. Max Shatalov – manager of SETi. They all serve in the session of environment/energy. They were impressed by an increase of the number of the submitted papers. To me, it seems to make sense. With the population of Homo sapiens increasing, the Earth is barely breathing. Without our effort, we will definitely engage into an irreversible future. As a result, taking care of the environment must become our priority, and I am happy to see research that is helping to make this possible.

 

They also told me about some interesting topics you should not miss:

1. Using the quantum cascade lasers for the environmental sensing: We are all very excited that QC lasers are finally portable and can be brought to the field for various applications. For example, trace gases like SO₂, methane, or air pollutants are all targets under the scrutiny of QC lasers. If you are a green-oriented person, you should not miss this opportunity when you come to CLEO: 2013. In addition, we were discussing a very interesting paper in which a laser is used to probe the “particle size.” Again, if you feel intrigued about it, you just have to keep your eyes open for topics like these while wandering around in the conference center.

2. Using UV-LED, for sterilization and water purification: This is a perfect example of how optical science is helping the humanity. UV-LED, being more compact and consuming less energy compared with traditional light sources, will probably become the main light source for food sterilization (in our discussion, UV-LED shining on strawberries was the content). The environmental impact of adopting this new light source into the food processing chain is self-evident. Cool science with a mix of practical goals – I guess this is yet another reason why CLEO is awesome.

3. Solar energy harvesting: How to harvest solar energy in a more efficient way is always an attractive scientific challenge for the researchers. In our short break, we touched on the topic of multi-junction cells, patterned surface — either nano or micro scales to trap more light into the solar cells, and using organic media to harvest the solar energy. Checking out the talk presented by Rebecca Jones-Albertus is a good entry point for you to delve into this domain.

 

In order to please the crowds of hard-core scientists, I also had a short chat with professor Zhigang Chen, who is serving for the CLEO: QELS Fundamental Science session of Nonlinear Optics and Novel Phenomena. He mentioned with zeal to me the breakthrough in plasmonic resonance, arbitrary trajectory manipulation of light propagation, using photonic periodic structure to test the idea of super-symmetry, and so on. The depth of the fundamental science he was trying to convey blows me away. Topics like these will always find their places in CLEO, and I always feel this is one of CLEO’s strengths. In fact, the entire QELS program poses a mental stimulus to my brain. These courses are so stimulating they are like “ “espresso for the brain!”

 

The truth is what I mention here provides just a small glimpse into all the great content being featured at CLEO. To get a glimpse at the full conference program, visit the CLEO website here!

 

View exclusive interviews with the Chairs and get more personal insight on hot topics and trends at CLEO: 2013

 

There is no break in the review conference. Everyone is eager to share their ideas. People were shuffling around to maximize their precious time together.

DISCLAIMER

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

Novel lasers shine and explore the new scientific frontiers – part I

To probe new scientific frontier, 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 evolves together to give us wonders and a better understanding of the universe and nature. Looking back in 2012, similar stories happened in 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:

In the old days (well, even in nowadays), to peek at the precise structure of a protein with the atomic resolution, you need to grow a “sizable” protein crystal such that you can use crystallography to decipher its structure. The reason is straightforward – without a sizable crystal, it cannot withhold the constant bombard from incoherent X-ray interrogation. However, growing a crystal made of protein is not easy. People used to joke that if a graduate student grew a big crystal, then he bought his ticket to a Ph.D. degree. That sort of tells us the difficulty.

With the advance of the femtosecond X-ray FEL, it gives us a new window. We do not need monster size crystal anymore. This “new light” is coherent which means it is intense and produces high-quality diffraction. On the other hand, its pulse duration is short (within tens of femtoseconds) such that the entire process ends before the onset of substantial radiation damage.

Researchers from SLAC National Accelerator Laboratory demonstrate this new technology beautifully to us. They use a 430 m long undulator to create femtosecond X-ray, either 5 fs or 40 fs pulse, with the wavelength of about 9.4-keV. The target is a liquid jet filled with micro-crystal of lysozyme (each crystal is less than 1 micrometer by 1 micrometer by 3 micrometer). The experimental setup is shown conceptually in figure 1. This result is very satisfactory and fits well with data that are gathered from traditional X-ray crystallography (figure 2).

Figure 1. The experimental set up of new crystallography realized by femtosecond X-ray FEL. Courtesy of S. Boutet and et al. in Science 337 362 (2012).

Figure 2. Part of the protein structure (electron density map) at 1.9 Angstrom resolution of lysozyme elucidated by this new technique. Courtesy of S. Boutet and et al. in Science 337 362 (2012).

Trivia about X-ray optics:

X-ray, although belongs to the family of electromagnetic radiation, has some interesting property which amuses me quite a lot.

1. First of all, it has index of refraction very close but smaller to 1. Figure 3 shows how index of refractions varies with the frequency of light. This means that its phase velocity is faster than light! Shocking! For people who are interested in this topic in more details, check this link out.
2. Normal mechanism we use to focus visible or IR light simply does not work in X-ray regime. For the reflective optics, X-ray only reflects efficiently if the incident angle is very shallow (close to 90 degree). If the incident angle is too small, the x-ray penetrates into the optics without being reflected. This phenomenon creates the need of special reflective optics, such as Kirkpatrick-Baez mirror to focus the X-ray (figure 4).
3. Just like I mentioned in above, the index of refraction of X-ray is just slightly below 1, we have to re-think how to focus X-ray if we want to use refraction principle. First of all, you have to think air as a glass, since air has index of refraction equals to 1, and the material has something smaller than one. A collimated X-ray will focus when propagating from the material to the air. Secondly, one refraction is hardly enough, since the index of refraction in the material is just slightly smaller than 1. As a result, to create strong optical power, you need many air bubbles in tandem buried in the material. The Be lens used in figure 1 has the structure like the picture shown in figure 5. For more description on the X-rays lenses, check out this website.

Figure 3. The index of refraction vs. wavelength. Courtesy of D. Attwood, an online resource.

Figure 4. An Kirkpatrick-Baez mirror to focus the X-ray.

Figure 5.  A beryllium lens with 20 lenslets in a 20 mm x 10 mm x 10 mm substrate (left). The lenslets are 5 mm deep. Courtesy of A.  Khounsary and et al. at  Beryllium and lithium X-ray lenses at the APS, an SPIE 2006 paper.

DISCLAIMER

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