Sunday, May 23, 2010

Last hours of CLEO/QELS

Before I finalize this post, it is very important to write something about the post-deadline session. Especially that it was outstandingly good! The quality of the talks and the work presented was amazing.

The talk on Coherent Perfect Absorbers, given by Prof. Douglas Stone from Yale University (QPDA5), was very clear and interesting. The authors propose a new idea of a perfect absorber, or a time-reversed laser, based on adding the right amount of dissipation under certain conditions and a certain illumination.

I would also like to mention a very artistic performance of Prof. Evgenii Narimanov from Purdue University (QPDA6), giving a talk on radiation-absorbing metamaterials. The authors developed a new approach to radiation-absorbing systems, based on the broadband super-singularity in the density of states of hyperbolic metamaterials. The broadband singularity leads to a dramatic enhancement of the light scattering from the defects and surface corrugations at the interface of the hyperbolic metamaterials, with nearly all the incident light scattered into the guided modes of the metamaterials. Hyperbolic metamaterials are materials that have one of the components of the dielectric tensor negative, so that in the k-space they are described by two hyperboloids, so that the phase volume and, hence, the density of states limited between them is infinite. The authors have experimentally demonstrated the reduced reflectance from the surface of hyperbolic metamaterials made of silver nanowires upon corrugation.

Another impressive talk was given by Ming Liu who presented A nano-scale light-driven plasmonic motor. The authors experimentally demonstrated that a nonoscale-size motor, based on a gammadion, can generate a sufficiently large rotation force being illuminated by linearly-polarized or non-polarized light. The authors embedded the gammadion in a micron-size silica disc, 4000 times larger than the motor, and demonstrated that the motor can rotate the disc in water. By changing the wavelength of light the authors were able to demonstrate the change in speed and direction of the rotation. A very impressive movie demonstrating the experimental realization of the motor has been shown. It was absolutely spectacular!

I also enjoyed the talk given by Dr. Marco Peccianti on Subpicosecond 200-GHz soliton laser based on CMMOS-compatible integrated microring resonatior (CPDA9). The authors approach involves a novel configuration that embeds the ring resonator inside a fiber-optic ring laser cavity. The nonlinearity and dispersion in the fiber-optic ring cavity induce the formation of the broadband soliton pulses. The material used in the microring device is the high-index doped silica. The authors experimentally demonstrated the performance of their device.

As the CLEO/QELS has ended, I am finishing this blog. It was a great conference and went very well for me, even though I am exhausted and need some time to process all the things I've learned. I hope you enjoyed reading this blog, and hope to see you all next year in Baltomore!

Thursday, May 20, 2010

More about interesting talks

Time flies so fast that I cannot keep up with posting about everything. Here are some interesting talks that I have attended on Wednesday and Thursday.

I was very impressed with the tutorial talk on terahertz quantum cascade lasers given by Dr. Kumar on Wednesday afternoon (CWF1). Typically, these devices operate at very low temperatures and need to be criogenically cooled. However, the operation temperature of terahertz QCLs gets higher and higher thanks to the new progress in the field.

I have attended most of the session on Nonlinear Integrated Optics, as this subject is of my primary interest. I liked the presentation given by Dr. Pasquazi on Net Parametric Gain in a High Index Doped Silica Waveguide (QWE1). The materials they used in order to obtain phase-matched four-wave mixing with a good efficiency was a special kind of glass, doped with some ions to have a nonlinear refractive index five times greater than that of SiO2, retaining at the same time the low linear and nonlinear absorption in the telecom range.

An interesting talk was given by Dr. Labukhin, in which a new method for modeling and controlling the nonlinear spatiotemporal dynamics of a semiconductor laser has been proposed (CWN6). In particular, the authors considered mode hopping effect exhibited by many lab semiconductor lasers, and studied its behavior under different conditions.

Prof. Shalaev from Purdue University presented a very good tutorial, in which he overviewed the recent progress in the field of tunable and active metamaterials (QThB1). Having many interesting potential applications, metamaterials still suffer from very high losses. This problem has been recently addressed by making the metamaterials active to compensate and even over-compensate the strong attenuation. Very recently the group of Prof. Shalaev was able to demonstrate such structures in the visible range.

Recent progress on chalcogenide-glass-based integrated optics has been reported by Prof. Luther-Davies (CCthW7). In this work, the authors investigated a new type of chalcogenide glass, having higher linear and nonlinear refractive indices compared to the earlier used chalcogenide glass As2S3. The authors fabricated nanowires in the new type of chalcogenide glass. Due to a higher refractive index, the new material enabled tighter mode confinement and resulted in a huge nonlinear coefficient. The authors were able to successfully realize supercontinuum generation in the new type of chalcogenide glass. Despite the 10 times higher nonlinear absorption coefficient compared to that of As2S3, the new material seems promising for wavelength conversion and other applications. I am looking forward to the published paper on this topic which I hope will become available soon.

Exhibit and Power Lunch

A good thing about the exhibit is that you don't have to submit and wait for a quote. It is simply enough to speak to a company representative to get an approximate idea about the prices, or sometimes even exact value. Walking around the exhibit, I've managed to get some things done, such as looking up an upgrade to our Coherent OPO and figuring out the pricing for certain items that I meant to check long time ago, always saving it for later. So, I've done my equipment homework.

Attending the Power Lunch, an event aimed at networking with industry representatives, I had a very good discussion with Dr. Andy Bairamyan from Lawrence Livermore Ntl lab. While being a student at the University of Rochester, I've been working at some point with Dr. Okishev and Dr. Zuegel on studying the laser performance of a fairly new crystal, Yb-doped GdCOB (gadolinium calcium oxoborate), first accidentally grown about 15 years ago. This crystal has a superior thermal and mechanical properties and a large transparency window, which makes it a perfect candidate for laser hosts and nonlinear materials. Strong second-harmonic generation has been realized in GdCOB and its relative YCOB earlier. In addition, it is very easy to grow this crystal by Czochralski pooling method to very large sizes with a very good uniformity. Since I started working on other things for my Ph.D. thesis I lost a track of the developments related to GdCOB and YCOB crystals. When I tried to speak to other people about these crystals earlier, not many people knew about them, as these crystals are new and their optical properties have been evaluated only recently. It turned out that Dr. Bairamyan is familiar with YCOB and GdCOB and aware about their excellent properties. Moreover, I've learned from him that these crystals are being actively used for harmonic generation, as they have better properties compared to other commonly used crystals, such as KTP. It was nice to speak to someone who dealt with the same material and updated me on its practical potential and applications.

Wednesday, May 19, 2010

Lasers rock!

And scientists do to. It was a blast last night! The concert was great! The performances were so professional that I could not believe these people scientists, not full-time performers. We were truly spoiled to have Sir Peter Knight as the program announcer.

The first performance was given by a duet of true rappers from Phat Photonics, Oregon Health and Science University. It was pretty entertaining. If not sophisticated witty wording of their master pieces, I would have easily confused them to professional rappers hired to entertain us.
"Light Amplification Stimulated Emission Radiation..." Does it sound familiar?

Eric Hansotte, local from San Jose, a graduate of the University of Rochester (same as me), an engineer, impressed us with his strong beautiful voice and the energy with which he delivered his performance. I liked how Peter Night announced Eric's performance, saying that Eric has to play music in the bars to financially justify his engineering hobby.

Two amazing highly-professional guitar performances, given by Yoshiaki Nakajima and Brian Kolner, impressed us with the complexity of music and technique that they had to apply to be able to make it sound. How people do that? Wow!

The Free Lunch band from Lawrence Livermore Ntl Lab made all of us wanna dance!!! Such a music, such a drive! Their singer had such a deep beautiful voice, and so much energy, that even the nerdiest of us could not help shuffling their feet in place, making small dance, while some other people just danced happily. That was absolutely awesome!!!!!!!!!

At the end of the concert we had Second and Third Harmonic Generation with Bob Fisher, Steven Block, and Tom Baer. They played Appalachian Fiddle Tunes, obeying at the same time the phase-matching condition for second- and third-harmonic generation by perfectly synchronizing with each other. They performed using a banjo, two mandolins, one guitar, and two harmonicas.

All these performances confirm how talented the scientists are, and not only in science! It all makes me feel proud for the wonderful people in Optics, for their creativity and talent.

Tuesday, May 18, 2010

Lasers and Waveguide Arrays

There are so many things per unit time happen at the conference that I cannot keep up with writing. So many interesting talks and events that it is not possible to write about everything and (I have to confess) recall all the details.

Yesterday and today I've been attending very interesting sections on novel phenomena. There have been a lot of works done in waveguide arrays lately, especially in 2D arrays, produced by femtosecond laser writing. I would like to especially mention the talk on 2D Dynamic Localization of Light, given by Dr. Alexander Szameit on Monday (QMA7). In that presentation, he told us about the observation of approximate dynamic localization in a 2D waveguide array, in which there were two layers of periodic structures, staggered with respect to each other. Optical analog of Bloch oscillations and dynamic localizations can be observed in coupled waveguide arrays under the condition of a gradient in the effective index from waveguide to waveguide, produced by the change of the waveguide width or by curving the waveguide array. You can excite one waveguide, and the light, instead of spreading all over the array because of diffraction, would relocalize in that initially excited waveguide periodically. This phenomenon has both fundamental and practical implications. E. g., one can make a narrow-band filter by properly design the waveguide array to exhibit the relocalization for a certain wavelength, so that at the output of the structure all the light would exit through the initially excited waveguide.

The soliton sections were expecially interesting. There is an increase in the number of experimental demonstrations of spatial solitons. I enjoyed the talk given by Y. Lamhot, Hot Particle Solitons (QTuC2). I have learned about a way of soliton formation by strong coupling between light and nanoparticles. The light heats the fluid containing the nanoparticles, which accummulate in the heated area and induce the effective refractive index change, influencing the guidance and causing the light self-trapping. I also enjoyed the talk given by Dr. Marco Peccianti, Optical Bullet Trains via Modulation Instability in Nonlocal Solitons (QTuC4). It is very impressive that it is now possible to experimentally observe such effects.

There were a lot interesting talks on semiconductor lasers. I found the morning section on 3-5 um Semiconductor Lasers very interesting. I've learned a lot about quantum cascade lasers and the recent developments and improvements to their performance. Another demonstration of a successful realization of a new semiconductor laser based on a Bragg reflection waveguide, which is a 1D vertical photonic bandgap structure with a defect supporting guided modes, was given by Bhavin Bijlani (CTuO5). He also gave a very interesting report on New Modality of Second-Order Nonlinearity in Bulk AlGaAs Bragg Reflection Waveguides later in the afternoon (CTuEE2). These reports together hold promise to realize the first electrically injected, self-pumped higher harmonic generation for applications including quantum optics. Using the sample platform for a difference-frequency generation process can also provide electrically injected sources to cover wide ranges of wavelengths in the infra-red. Don't miss another related talk tomorrow (QWE2)!

As I am finishing, it is time for the CLEO Welcome reception and the Lasers Rock! concert. More networking, more fun!

Monday, May 17, 2010

Celebrating Laser's 50th Anniversary

I took this picture when arriving to San Jose Convention Center to collect my badge and conference materials package at around 2:30 p.m. on Sunday. CLEO/QELS 2010 has began and welcomes us!

I've been looking forward to the 50th Anniversary of Laser symposium. Like many of you, I am sure. It was surprising how many people succeeded to arrive that early to attend this remarkable event. I almost felt spoiled having so many distinguished scientists in one session. The memories in their presentations were flashing at us with the old scanned photographs, original hand-written equations and raw data collected with the first laser, together with the well-known pictures and graphs from the old articles that we have seen used in the Lasers textbooks. It truly makes you feel like you are in the middle of some significant experiment, at the edge of the great discovery - the Laser.

The Symposium started with the opening words by Prof. Konstantin Vodopyanov from Stanford University. The first symposium speaker was Kathleen Maiman, Theodore Maiman's widow. I have learned from her and from the next speaker, Jeff Hecht, who is an independent science and technology writer, about the unique personality of Theodore Maiman that enabled him to accomplish the first demonstration of laser radiation with ruby. He had to face a lot of "It's not gonna work," but the discouragements did not stop him, did not turn him away from his great goal. It took a person with Theodore Maiman's mindset to achieve the first demonstration of laser generation. Luckily, such a person was there, just at the right time, to succeed.

Profs. Tony Siegman and Orazio Svelto, the authors of two famous books on lasers, chronologically outlined the events associated with the first laser demonstration. Prof. Siegman spoke about laser resonators and the famous Fox and Li theory of modes in a plane-parallel laser cavity and about the first resonators. I still remember reading throught he original 30-page paper in Bell Systems Technologies Journal, 1961, and all the slides with the pictures from the paper seemed so familiar.

Prof. Nicolaas Bloembergen, who shared the 1981 Nobel Prize in Physics with Arthur Shawlow and Kai Siegbahn for their work in laser spectroscopy, shared with us some recollections about ruby masers and lasers. Prof. Charles Townes, the pioneer in maser invention and a witness of the first laser, told the actual story how it all happened and how the first maser saw the world. He also mentioned that Russian scientists Basov and Prokhorov independently developed the idea of maser in Soviet Union and shared the 1964 Nobel Prize in Physcics with Townes.

Dr. Kumar Patel from Pranalytica, Inc. told about the arrival of the first high-power CO2 lasers and about the development of quantum-cascade lasers. Dr. Marshall Nathan from IBM shared with us his story about the realization of the first semiconductor laser at IBM. The session was concluded by Dr. Edward Moses from Lawrence Livermore National Laboratory who shared with us the news about the recent progress in Inertial Confinment Fusion (ICF) experiments, achieved at the laboratory, and national ignition facility, that makes it likely for ICF to go live within the next couple of decades to produce a new source of power. I liked his recollection about his first experience with lasers, in which he tells that as soon as he saw HeNe laser extending its beam across the room, he realized that he will follow this beam for decades.

It all went very well, and was very interesting. Before my post is too long, I'd better stop to continue later about other CLEO events. It is never enough when you are writing about something as significant as the first laser.

Sunday, May 16, 2010

What's Hot from the U of Toronto

Before the conference started, let me overview some upcoming interesting talks that I already know something about. These are presentations by the Photonics Group at the University of Toronto. I am sure that CLEO/QELS attendees will find quality research and exciting new results there, so I would like to give you all some heads-up.

It just takes a twist...
Due to the symmetry considerations, the second-order nonlinear susceptibility tensor in poled fiber exhibits forbidden components, so, no second-harmonic generation associated with those components is possible. Eric Zhu from Prof. Qian's group will be talking about how one can observe, and even enhance those components by merely twisting a fiber. The same tensor components are responsible for the reverse process, parametric down-conversion, so important for quantum imaging. (CTuEE6, 3:45 p.m., Salon I and II in Marriott)

Anti-guided waveguide lasers
This sounds controversial, isn't it? Bhavin Bijlani from Prof. Helmy's group will tell us about his work on edge-emitting Bragg reflection waveguide laser. He will demonstrate the results of the laser performance and talk about the design of this device. Search for novel semiconductor laser sources is important for Integrated Optics. (CTuO5, 11:45 a.m., room A6)

Photonic crystal biosensors
Guided resonances in photonic crystal slabs exhibit important qualities for sensing applications. Mohamed El Beheiry from Prof. Levi's group is going to demonstrate to us, through simulation and experiment, the enhanced sensitivity and differences in properties between TE- and TM-like guided resonances in biosensing. (CtuN4, 11:15 a.m., room A4)

Difference-frequency generation in quasi-phase-matched semiconductors
It is tricky sometimes to get the parametric nonlinear optical processes to work out. They require phase matching which is difficult to achieve. Quasi-phase-matching technique, in which the nonlinear susceptibility is periodically modulated, allows one to significantly increase the efficiency of a nonlinear optical process. Sean Wagner from Prof. Aitchison's group will tell us how he managed to obtain difference-frequency generation in quasi-phase-matched superlattice AlGaAs waveguide, converting C-band signal to L-band and U-band. In this case, difference-frequency generation helps one to expand the useful bandwidth in the telecom range beyond the EDFA working spectral window. (CThEE4, 5:30 p.m., Salon I and II, Marriott)

Modulation faster that relaxation
Wesley Sacher from the Prof. Joyce Poon's group is going to demonstrate laser modulation
at rates greatly exceeding the relaxation resonance frequency by modulating the output coupler.
It is very important to be able to modulate the laser faster that its relaxation frequency. In this case, one can get rid of the relaxation oscillations while being able to imprint the useful data into the optical beam by the modulation. Wesley will show how he succeeded to modulate an erbium fiber laser 10000 times its relaxation resonance frequency.
(CFE4, 9:00 a.m., room C3&4)

Resonant transmission of subwavelength apertures
Enhanced transmission that the subwavelength apertures can exhibit under certain conditions has been a subject of interest from both fundamental and practical points of view. Bo Hou from the Prof. Poon's group is going to demonstrate the measurements of infrared light transmission through subwavelength H-shaped aperture arrays in gold. (CFM4, 11 a.m., Ballroom IV, Marriott)

I have arrived to San Jose and already visited the campus of Stanford University with its beautiful buildings made of yellow stone, narrow long passages with columns, and exotic California trees and plants everywhere around the campus area. It's cool to have the conference in such a nice location with such gorgeous nature and top universities around. It makes your mind clear and gives you the right mood to make this conference everebody's and your personal success.