6 Year Reunion
From Left to Right: Heather Ferguson (UM PhD program-EE), Alex Fisher (UM PhD program-EE), Mason Carney (U. Leiden PhD program-Physics), Michael Abere (Post Doc, Sandia National Labs)
Not Pictured: Amy Claeson (U Minn. PhD program-BME), Pavel Chvkov (MIT PhD program-Physics)
Last Day of the Program
(not pictured, Pavel)
Advisor: Guilhem Gallot
I spent my summer in Paris working in Le Laboratoire d’Optique et Biosciences with Dr. Guilhem Gallot and his Ph.D. student Antoine Wojdyla, while also maintaining contact with University of Michigan advisor Dr. John Whitaker. My project involved analyzing a new method for cross-sectional beam analysis of ultrafast terahertz (THz) pulses using an ultrafast shutter made of a silicon wafer and optical excitation pulse. The method worked by inserting a silicon wafer of 0.5 mm thickness in the THz focal area of a standard pump-probe THz generation scheme.
It was possible to control the amount of THz passing through the silicon wafer by locally exciting the semiconductor. This was possible because THz radiation will transmit easily through silicon with little attenuation, but will completely reflect when electrons in the wafer are optically excited to the conduction band. By focusing an 800 nm optical beam to a size of approximately 5% of the THz beam width, it was possible to raster the THz beam over a cross-section of the beam and create an accurate beam profile. By taking waveform data at each point along this scan, it was also possible to obtain spectral information on our beam.
My experience in Paris was unforgettable and this program gave the chance to open up my eyes to a whole new world of research, culture, and living. The REU was a great balance between working hard to produce meaningful results and having the time of my life in one of the most interesting and cultured cities in the world.
Advisor: Sylvie LeBrun
I worked at École supérieure d'optique conducting research on Raman scattering, a process that involves the absorption and re-emission of light in the nonlinear optics regime via the vibrational states of an atom or molecule. By controlling the nonlinear characteristics of the Raman effect in liquid-filled hollow-core optical fibers we created a highly efficiency wavelength converter that was based on the nonlinear properties of the liquid and the wavelength of excitation light injected into the fiber. I used a pulsed, nanosecond Nd:YAG 1064 nm crystal source that was frequency-doubled to emit a 532 nm beam at 0.66 ns pulses. Ethanol and water were used to fill the optical fiber for the investigation of pulse frequency dependence of certain characteristics of Raman scattering, including conversion efficiency and Raman threshold peak power. The hollow-core optical fiber possesses a certain bandgap, meaning that only a certain wavelength range can pass through the fiber. By choosing the correct liquid and wavelength of excitation light, we sought to produce a single order output wavelength with optimal conversion based on the peak power of the beam. In addition, I tested the method of light injection into a hollow-core optical fiber by comparing a free space injection to the coupling of a photonic crystal fiber with a conventional silica optical fiber.
Advisor: Cedric Bouzigues
The purpose of my project was to induce cellular uptake of a recently published probe (Casanova et. al., 2009) within cells growing in microfluidic channels. The probe consisted of Y0.6Eu0.4VO4 nanoparticles, which could detect reactive oxygen species during cellular signaling. The nanoparticles photoreduced under laser irradiation but re-oxidized when oxidants were present. The probe is not specific to hydrogen peroxide signaling, but hydrogen peroxide is the most prevalent oxidant in many signaling processes. My specific responsibility was to develop and validate a protocol for the pinocytosis of nanoparticles into HeLa cells seeded in microfluidic channels.
I learned a multitude of new skills working under Cedric Bouzigues during my two months at the LOB. Most notably, I learned (1) how to work with PDMS to create microchannels, (2) cell culture, and (3) how to sort and count nanoparticles. The most exciting part of the project was when my protocol finally worked and was able to see the fluorescing nanoparticles within the living cells in the microchannels. I validated the protocol by photoreducing the nanoparticles with a laser, and then I added a volumetric flow of hydrogen peroxide to the microchannel, which oxidized the nanoparticles causing them to re-fluoresce within the cells.
Seeding the cells in microchannels will allow the lab to test what concentrations and flow rates of certain molecules activate the release of hydrogen peroxide in cellular signaling pathways; the presence of which is detected by the nanoparticle probe.
Casanova, D., Bouzigues, C., Nguyen, T. L., Ramodiharilafy, R. O., Bouzhir-Sima, L., Gacoin, T., et al. (2009). Single europium-doped nanoparticles measure temporal pattern of reactive oxygen species production inside cells. Nature Nanotechnology, 4(9), 581-585.
Advisor: Igor Martial
While in Paris, my project's focus was laser amplification in Nd doped YAG crystal fibers. I worked at the Institut d’Optique under Igor Martial. The idea of a crystal fiber is to implement the best things about both crystals and fibers. In crystal amplifiers the pump and laser are unguided, while in fiber amplifiers both the pump and laser are guided. In fiber crystals the pump was guided through, however the laser was unguided. We looked at computer simulations to determine the best position of the pump and laser. We also recorded data for crystals of varying concentration of dopant. We received some very promising results, which led to a conference paper. However, in the end, the project was limited by a thermal shift in the luminescence to where it no longer coincided with the laser. I gained a lot of experience in working in an optical lab, aligning equipment and how to use it properly. I also had the opportunity to attend several talks and get a sampling of what was being pursued on the field of optics.
Outside the lab, I had a great time and was welcomed readily into the group of graduate students at the Institut d'Optique. The summer gave me a look into what graduate school could be like. It as so gave me a taste of French culture and language.
Advisor: Gerard Moreau
An ultrafast laser irradiation method for the removal of corrosion from Daguerreotypes without detrimentally affecting image quality has been developed. Corrosion products such as silver oxide and silver sulfide may be removed by chemical cleaning but these reactions are hard to control and often damage the underlying silver and image particles, ruining the image. The 150 fs Ti:Sapphire laser pulses used in this study are focused to a beam diameter of 60 μm and are normally incident to the Daguerreotype. It was found that the corrosion layer has a lower material removal threshold than silver allowing for removal of corrosion without damaging the substrate or changing the size and distribution of the image particles. A model in which the interface between the corrosion layer and underlying silver plays a significant role in material removal will be discussed
Advisor: Gerard Moreau
My project at Laboratoire D'Optique Appliquée was on measuring the dynamics of ultrafast plasma formation in He. The setup and the experimental tricks that I used for this were quite fun and intellectually engaging. The basic concept was a pump-probe setup, with the 10fs pump beam being focused into a He jet to form a plasma, and the weaker probe split off and focused transversely at that same cite of plasma formation, with a variable delay. To resolve the stages of He ionization on such short time-scales, the appropriate variations of probe beam path were on the scale of microns, and required a piezoelectric translation stage. The probe beam was then sent to a spectrometer and the blueshift due to its passing through a forming plasma was measured. Playing with many of such cool physics concepts and utilizing them to achieve my goal was a really exciting experience.
The rest of my time in Paris, I explored the city, went to museums, learned French, played Ultimate Frisbee with a local community and got to know some students form École Polytechnique, and found that I really enjoy the French culture. It was a great experience, and I highly recommend it to anyone!