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Jun 10

imageAfter many hours of flights, I finally arrived in San Jose, CA for this year’s CLEO meeting. I made my way downtown and shortly headed over to the Convention Center to pick up my registration materials. Conference program and other goodies in hand, I headed back to my hotel to dive into the details of what’s in store for this week.

As is typical when I attend CLEO, I found that the conference is filled with more information than one person could possibly hope to absorb in a single week. The conference lives up to its name: lasers and electro-optics, everything from laser science to photonic applications. And what an incredible mass of information is contained therein. Just a quick glance can give you an idea of the technical reach of the conference; from a ten-thousand-foot view, you can see a plethora of lasers, nanophotonics, novel optical materials, quantum optics, biophotonics, plasmonics, nonlinear optics… it’s hard to wrap one’s head around it all!

For my part, I’m a bit daunted by the prospect of having to narrow my choices down to just the handful of sessions I’ll be able to attend. I did, however, manage to pick out a few that I’m particularly interested in checking out. These include the symposium on high power diode laser arrays and the special technology transfer program. I immediately added these to the Guidebook app on my phone. (For those with a smartphone, you can use the Guidebook app to view all kinds of conference info and create a schedule of the sessions you’d like to attend.) I’ve still got a bit to go before I narrow down to my top choices, but that’s part of the fun of CLEO: there’s so much going on at once, you can wander into just about any room and see an interesting and educational talk.

With that, I’d like to welcome all the attendees who made it to CLEO: 2013! As is usual for this conference, it appears we have an exciting and full week ahead of us. I’m eagerly awaiting the conference getting into full swing tomorrow. Now I just need to figure out what talk I’m going to see first….

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.

May 29
Example of a Photovoltaic wall

Photovoltaic wall at MNACTEC Terrassa – courtesy wiki commons

This year’s CLEO Conference, sponsored by APS/Division of Laser Science, IEEE Photonics Society and the Optical Society includes S&I 15: LED, Photovoltaics and Energy-Efficient (“Green”) Photonics which is part of the Science & Innovations technical program. Tom Giallorenzi, OSA’s Science Advisor interviewed Jonathan Wierer, Sandia National Laboratories, USA, Photonics, Subcommittee Chair, S&I 15 to find out about some of the trends for this year’s hot paper submissions.

Tom Giallorenzi:               Can you review the talks that you got and were there any themes or any outstanding trends that you were able to discern?

Jonathan Wierer:             We have a tutorial by Seth Coe-Sullivan on colloidal quantum dots and then there were a few quantum dot submissions and one of them is by a student from Bilkent University.

He’s going to be talking about putting colloidal quantum dots into an LED structure.  And the problem is the quantum dots are very small materials, and it’s not your typical planar PN junction where it’s very easy to make contacts and inject current and produce light.  Now you have these small little quantum dots and the question is how do you put current into these quantum dots?  So they’re putting these quantum dots into polymers that facilitates injecting current into them.  And so that’s not necessarily new, but they’re trying to engineer the polymers to make that energy transfer from the polymers to the quantum dots more efficient.

Tom Giallorenzi:               And did you get  any papers on energy efficiency?

Jonathan Wierer:             They’re all on energy efficiency.  If I have an LED talk,  nine times out of ten, they’re talking about making the LED more efficient. This quantum dot talk I was talking about from Bilkent University, the quantum dots are very efficient.  So if I photo pump them, hit it with a laser and see how many photons I get out, that process is very efficient.  What’s not efficient is trying to put it into an electrically injected structure.    And so they’re trying to learn how to make that injection more efficient.  And on the flip side, for example, this tutorial from Takashi Fukui, he’s trying to make nanowire solar cells more efficient.  And if the solar cell is efficient, naturally your systems’ more efficient; you can harvest more of the sun.

Tom Giallorenzi:               Could you characterize the energy program at CLEO this year?

Jonathan Wierer:             So, for the energy efficiency CLEO programs, there’s two of them.  The SI 15 is more on the device and device physics side and it covers LEDs and solar cells, but then we have  a sister program going on that’s A&T 2 and there, they’re also concerned with energy and the environment, but it’s more at a system level.  So you’ll see talks about LEDs,  but at the system level, where they’re applying these sensors that are more energy efficient.  So, it’s nice,  you have these two sets of talks and they span the gamut from device physics up to the system level.  So it gives you a nice broad cover of the energy sector.

Tom Giallorenzi:               Why would somebody in the energy field want to come and hear some of these talks?

Jonathan Wierer:            If you’re interested in solar, there’s a lot of strong talks covering enhanced absorption by using light trapping and plasmonic structures.  And if you’re a researcher working in the solar field, that’s very interesting because it leads to a reduced amount of material that you have to use.  And so there’s a lot of strong talks from students in the field that are up and coming and if I’m a solar guy at a solar company, not only do I want to find out if  this information is useful for my company, but also I want to make connections with the students for the company’s future.

On the LED side, our invited talks play right into solid-state lighting.   Using colloidal quantum dots for solid-state lighting and using nanowires for LEDs are hot topics.  These talks are from two different companies.  So they’re being implemented, and I think that’s probably really interesting for anybody in the LED field.

Tom Giallorenzi:               When you say that we can implement it, are they in commercial products?

Jonathan Wierer:             Yes, you can find some commercial products with colloidal quantum dots.

Tom Giallorenzi:               And how much of a difference do they make?

Jonathan Wierer:             So, for example, colloidal quantum dots can do things that conventional LEDs can’t.  Seth Coe-Sullivan will talk a little bit more about it, but in the red, current LED technologies have some limitations.  And the colloidal quantum dots may be able to help in the red;  to reach efficiencies that you can’t get with conventional LEDs.

Tom Giallorenzi:               What are some of the big reasons you think I should attend my CLEO?

Jonathan Wierer:             One of the reasons why I like coming to CLEO is because there are always a lot of good excellent talks.  CLEO has a very good reputation.

Not only is it a good way to see all these excellent talks, it’s also a way to meet these people face to face, to have interactions with them. That actually goes a long way for me personally.  I have to make these connections and to try to build future research and programs, and maybe there’s common ground where we can work together. It’s just one of the reasons why I come here.  Nine times out of ten, you can read what’s going on in the literature.  I can sit at my desk, get on the computer, and read what these guys are doing.  But actually coming to a conference, meeting the person, making a connection, it just takes it another step.

Tom Giallorenzi:               Thank you very much.

For more information on the Science & Innovations program, visit for more information.


May 23
S&I 8 Subcommittee Chair

Gunter Steinmeyer, Max Born Institute, Germany, Subcommittee Chair, S&I 8
Click on Image to View Video Interview.

This year’s CLEO Conference, sponsored by APS/Division of Laser Science, IEEE Photonics Society and the Optical Society includes S&I 8: Ultrafast Optics, Optoelectronics and Applications which is part of the Science & Innovations technical program. Tom Giallorenzi, OSA’s Science Advisor interviewed Gunter Steinmeyer, Subcommittee Chair, S&I 8: Ultrafast Optics, Optoelectronics and Applications, to find out about some of the trends for this year’s hot paper submissions.

Tom Giallorenzi:         Can you highlight an invited paper or two?

Gunter Steinmeyer:     Among the invited papers, there is one paper that reflects general trends – that we also see in the submitted papers and there is now a lot of papers about optical parametric schemes for generating short pulses, in particular in the mid-infrared for generating extremely broadband radiation that can be compressed –  back into a short pulse.

Tom Giallorenzi:         What is the interest in doing it in mid-infrared?

Gunter Steinmeyer:     In the mid-infrared, there’s a high interest because if you drive attosecond pulse generation schemes –        you are hoping to get a much higher cutoff, and much higher energies.  So the hope that is connected to these sources is basically x-ray generation at shorter wavelengths than can be – achieved with high harmonic generation schemes nowadays.

Tom Giallorenzi:         We have one of the inventors of the attosecond science giving a plenary talk.  Could you say a little bit about him?

Gunter Steinmeyer:    Paul Corkum will be giving a plenary talk on attosecond pulse generation.  He’s one of the pioneers in the field, and particularly on the theoretical side.  He explained high harmonic generation.  I think he’s one of the first scientists and also the inventor of many different schemes that have now been employed and tested for attosecond pulse generation.

Tom Giallorenzi:         We’ve heard a lot about attosecond pulses.  What would you say is the – forefront in the research these days in attosecond?

Gunter Steinmeyer:     The forefront in terms of pulse duration, I think the shortest I ever heard of it sub-70 attosecond pulse and – I think these are very sophisticated schemes that also address the dispersion of these very challenging wavelengths.

Tom Giallorenzi:         Why would it be interesting to attend the sessions?

Gunter Steinmeyer:     This year in my topical area, there are some, I think, new emerging trends  or strengthening trends that we’ve already seen in the last years.  One of them is definitely optical parametric pulse generation schemes and there’s a lot of contributed papers.  There’s also an invited paper on this topic.

hese papers focus on the generation of few-cycle pulse shapes in the mid-infrared, which is an important driver wavelength for attosecond pulses.   Then, there are a lot of contributed papers concerning the control of the carrier-envelope  phase.  This has actually surprised me that there’s now still so many papers, and this is really exploding a little bit.    And then there are also very interesting papers concerning the generation of  coherent supercontinua which can be compressed back into very, very short pulses covering only like one or two cycles in the envelope.

Tom Giallorenzi:         Can you say a little more about that, what’s the importance of carrier-envelope phase stabilization?

Gunter Steinmeyer:     Carrier-envelope phase stabilization is one of the key technologies for making attosecond pulses.  Without having a carrier-envelope phase stabilized driver pulse train, you basically only end up with random attosecond generation, only every, I don’t know, -  tenth pulse or so is actually really a short and useful attosecond pulse.

Tom Giallorenzi:         And this allows you to make them stable and hit every pulse?

Gunter Steinmeyer:     It allows you to generate stable attosecond pulse trains –  that can actually really be used in an easy way in an experiment.  Otherwise, you could only use every tenth and always have to measure the carrier-envelope phase on the side and then later sort out of which of the events were useful and which are not, and the shorter the pluses get,   probably, the less efficient your scheme will get if you don’t have this carrier-envelope phase stabilization.

 Tom Giallorenzi:         If you had to summarize what are the frontiers in nonlinear optics?

Gunter Steinmeyer:     Yes.  So, one of the invited papers in S&I 8 is an invited talk about the higher order – Kerr effect, and this is one effect that has caused a lot of discussion in the recent years, and I think this is one of the discussions that is moving at the limits of our current –  understanding of nonlinear optics.

Tom Giallorenzi:         Why is the Kerr effect important?

Gunter Steinmeyer:     The Kerr effect is important, for example, to understand filamentation.  Optical filamentation has recently always been discussed that it can only be caused by plasma generation.  Now there are indications that filamentation could be possible, maybe not at 800 nanometers, maybe at longer wavelengths due to this higher-order stabilizing Kerr effect, and such a filament, if exists at all would then be dissipation-less. So you wouldn’t have to generate the electrons which will, I mean, eventually bleed out all the energy of your pulse.

Tom Giallorenzi:         So this would potentially allow you to propagate in a filament for a very long reach?

Gunter Steinmeyer:     Yes.  That would be one of the implications.

Tom Giallorenzi:         Are there other implications?

Gunter Steinmeyer:     There is, of course, a strong connection also to higher-order harmonic generation – and then again to the attosecond pulse generation schemes.

Tom Giallorenzi:         Could you repeat that by saying some of the – it’s a – if you can, repeat the question.

Gunter Steinmeyer:     Another implication or another connection of the higher order Kerr effect is to high-high harmonic generation.  Basically, this is the refraction twin of these generation schemes and consequently, there’s also a link to attosecond generation schemes.  Therefore, I think this effect is highly interesting.


For more information on the Science & Innovations program, visit for more information. For more exclusive insider info on trends in ultrafast optics, view the video interview.

May 21
There is no break in the review conference. Everyone is eager to share with others about their ideas. People were shuffling around to maximize the precious time together.

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.

By Frank Kuo – Paramountist Blog

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.

May 09

Jacob Khurgin, General Co-Chair, QELS-Fundamental Science

Jacob Khurgin, General Co-Chair, QELS-Fundamental Science

Attosecond Optics & Other Trending Hot Topics at QELS-Fundamental Science Conference

This year’s CLEO Conference, sponsored by APS/Division of Laser Science, IEEE Photonics Society and the Optical Society will feature an exciting number of submissions to QELS- Fundamental Science in the area of attosecond optics.  Tom Giallorenzi, OSA’s Science Advisor interviewed Jacob Khurgin, General Chair, QELS-Fundamental Science to dig deeper into the hot topics for this year’s QELS- Fundamental Science Program

Tom Giallorenzi: Why is CLEO a must-attend conference?

Jacob Khurgin: If you look at other conferences, which I would not name, they might be bigger, they can cover wider area, but I know of no conferences which have such a rigorous reviewing process.  And I’m talking not just optics conference because … I’m also active in condensed matter physics and semiconductors and so I think we emphasize quality over quantity. You cannot go to every conference, but I’ve been going to CLEO for 30 years now.

Tom Giallorenzi:              

Can you give us some of the research highlights and trends at this year’s QELS- Fundamental Science Program?

Jacob Khurgin:  

Yes, so the section of CLEO which I present here is dedicated to fundamental science, even though it’s a fundamental science, the trend has been to miniaturization and practicality.  And all the experiments which used to be done in large labs with high fields maybe high magnetic fields, huge, huge lasers for high lag optical fields and high vacuum is migrated.  First, it’s migrated to tabletop and what we now have started seeing is that it’s migrating to optical fiber, like crystal fiber, hollow core fiber, and more interestingly, it’s migrating towards integrated optics. 

So, we’ll have presentations where high field nonlinear optics is demonstrated in essentially integrated optical devices which, while I would not say they’re compatible with electronics right now, but the trend is towards compatibility and functionality. 

 There are lots of papers in the emerging fields of plasmonics and metamaterials and again, they’re becoming more functional. It’s not just to press light from Point A to Point B, but to manipulate the light and combine on the same integrated platform electronics and then high magnetic field some modulation, optomechanics and plasmonics.  I think plasmonics and optomechanics, … that’s a new trend because plasmonics provides for high field and miniaturization, which is difficult to achieve otherwise. In terms of condensed matter optics, the new trend is novel to 2D materials beyond graphene.  Of course, everyone heard about graphene, which has been discovered –maybe less than a decade ago and lots of work was done.  It was this exciting material.  Nevertheless, it’s limited because it is essentially a conductor.

But now we have new materials such as boron nitride, molybdenum compounds, which are also two-dimensional materials, but they exhibit the whole range of properties from good conductor to very strong insulator –with – and no semiconducting state in between.  There will be lots of presentation of these new and exciting materials. 

But I think the biggest trend is attosecond optics because we have seven subcommittees and almost all of them present attosecond optics so basically optics in which the length of the pulse is only a few optical cycles, which is interesting by itself.  It’s interesting as an instrument to study condensed matter.  It’s interesting as a nonlinear switch and it’s interesting in combination with plasmonics and metamaterial.

And up until recently, it was inaccessible, maybe one or two labs in the world could do it and now it becomes a standard instrument.  And I expect that ten years from now –attoseconds will go to the different part of CLEO, basically applications will all be real world applications there.  That’s trends.

Jacob Khurgin is a professor at Johns Hopkins University and serves as General Co-Chair of QELS-Fundamental Science for CLEO, Conference on Lasers and Electro-optics. For more information,

May 05

Technology Transfer Sessions


Attendees engaged in a 2012 CLEO: Tech Transfer Session

As part of the Exhibit Hall and related activities, CLEO: 2013 will be featuring a special program on technology transfer. The sessions will include a number of displays and talks related to the topic. One segment of the program will include a designated area for organizations to showcase their ideas that are ready to be transitioned to the commercial sector. In addition, there will be a number of talks related to technology transfer.

Several talks will center around advice and lessons learned for the technology transfer process. In particular, two tutorials will cover “Technology Transfer 101: Technology Licensing and Tech Startups,” given by Eugene Cochran and Anis Rahman. Additionally, a keynote speech will be presented by Prof. Robert Norwood of University of Arizona. Prof. Norwood will give a personal account of his experiences with a photonics startup company and the inherent challenges and lessons learned.

This technology transfer session is a good example of how CLEO goes beyond being a pure science conference. This looks like a great opportunity to learn about the ins and outs of technology transfer from some people with extensive first-hand experience. It should be very informative for entrepreneurs or those who are just interested on how technology can move from ideas to products. Be sure to check out the exhibits June 11-13 and the talks on Thursday, June 13, all in the CLEO Exhibit Hall Session Area.

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.

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

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.


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.


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 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 »

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