APPLIED OPTICS. List of projects Spring

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1 Portland State University A. La Rosa APPLIED OPTICS List of projects Spring Smith Aarisa Photoactivatable Push-Pull Fluorophores and their Use in Imaging Single Molecules in Living Cells Photoactivatable fluorophores have been used for some time in the sequencing of DNA and for nonliving molecules. New research has allowed their use in living cells, giving a real-time window on the operation of life at a molecular level. The use of these molecules in living cells has certain requirements beyond their use in molecular applications. These requirements include photostability, activation at a wavelength that will not induce autofluorescence of the cells themselves, and so forth. In order to understand how these cells assist in imaging life photon by photon at a resolution below the diffraction limit, we will evaluate their design criteria, mechanism of operation, and the technologies applicable to achieving this ultimate resolution. To put this in context, a brief review of some of the current research and uses of these molecules will conclude our discussion. The primary article that will be reviewed will be Lord, Conley, et al. A Photoactivatable Push-Pull Fluorophore for Single-Molecule Imaging in Live Cells, J. Am Chem Soc 2008 July 23; 130(29): Available online at along with the supplementary material provided by the authors in a pdf at the end of the webpage. Additional information sources may be used, including the article listed on the project page, Schwartz and Patterson, Development and use of Fluorescent Marker Protei ns in Living Cells, sciencemag.org, 13 April 2008 The following article, and others may also be referenced: Fernandez-Suarez, Ting. Fluorescent probes for super-resolution imaging in living cells. Nature Reviews Molecular Cell Biology 9, (December 2008), available at: Sabrina Hoffman Ultra-High resolution imaging by fluorescence photoactivation localization microscopy, by Samuel T. Hess, et al. Hess et al discuss a new method for fluorescence imaging that can attain ultra-high resolution images on length scales shorter than the classical diffraction limit. This method, called fluorescence photoactivation localization microscopy (FPALM), analyzes thousands of single flourophores per acquisition. This is done at low excitation intensity, where photoactivatable green fluorescent protein are activated by a laser first at high frequency then at low frequency. Molecules are removed from the field of view by photobleaching them, and since a small number of molecules are visible, their position can be determine with a precision as much as 10-fold

2 better than the resolution. This allows for biological imaging of topics before limited by microscope resolution now available for observation. Outline: Introduction-The faults of other imaging methods Why this method allows for ultra-high resolution Photobleaching and photoactivation and how it plays into FPALM. Theory behind FPALM Overview of the papers methods Results and their conclusion Limits of FPALM method Conclusion Kelsey Adams Classical Analog of Electromagnetically Induced Transparency Summary: In the paper Classical Analog of Electromagnetically Induced Transparency, the authors connect the phenomenon of EIT to a classical system of two coupled harmonic oscillators. Because EIT is a coherent event, it can be mirrored in such a classical system and many characteristics from the effect are reproduced by the classical system. The paper then describes how to model the classical analog with an RLC circuit. I plan to expand on electromagnetically induced transparency and how it relates to controlling the speed of light. Slow light can be brought on by EIT, and the dispersion that causes it would also be observed as an effect of the analog of EIT described in their paper. EIT occurs when light with frequency f 1 is incident on a medium that absorbs it well. The absorption line for the medium would then have a peak at that frequency. However, when a second light with frequency f 2 is absorbed by the medium, the initial peak at f 1 splits in two. The medium becomes transparent to that frequency and no longer absorbs it. The setup explained in the paper is that of a three-level atom. The probe laser excites the first quantum state in its ground state to a third state. The pump laser then excites the second quantum state to the third state. The probability amplitudes of the excited quantum states interfere destructively, and the frequency from the probe laser is no longer absorbed by the medium. Slow light is a consequence of the decrease in the group velocity of the wave. The group velocity of light depends on how the index of refraction changes with respect to the frequency. This is essentially a dispersion relation: a relation between w, the angular frequency, and k, the wave number. This relation determines the phase velocity, w/k, which in turn determines the index of refraction: n=v/c. In EIT, the different frequencies invoke different indices of refraction, and this large change in the index affects the group velocity. The group velocity can be increased as well as decreased because of this phenomenon. It is also possible for the wave packet to actually stop within the medium. Controlling the speed of light is largely due to the change in the refractive index of the medium, and is not only observed as a result of EIT, but many other experiments that affect the dispersion relation. References C. L. Garrido Alzar, C. L. Garrido Alzar, P. Nussenzveig. Classical Analog of Electromagnetically Induced Transparency. American Journal of Physics 70, (2002). Joel Paddock Alzar, Martinez and Nussenzveig have proposed a phenomenological model of electromagnetically induced transparency (EIT) that uses a coupled pair of classical harmonic oscillators, which can be realized with analog electrical components in an RLC circuit.

3 In this paper, I will review the analogy between the optical response, i.e. the dispersion and absorption responses found in EIT, and the frequency response of the resonant electrical circuit. A key point of interest is the similarity between the group velocity in the optical system as determined by its dispersion relation, and the group delay in the electronic system determined by its frequency response. A simulation of the circuit of Alzar et al with a narrow band pulse will be used as a qualitative demonstration of slow light phenomena. Table of Contents: 1) What is EIT? 2) Model: coupled classical harmonic oscillators 3) Qualitative comparisons between optical response and oscillator frequency response a) Relation between optical response and group velocity b) Relation between circuit s frequency response and its group delay c) Worth mentioning: Kramers-Kronig relations, and Bode relations 4) Simulation: a delayed pulse as a conceptual demonstration of slow light Mitch M. Long Plasmons A plasmon is a quasi-particle, not an actual particle, but a quantized oscillation in a plasma. When certain wavelengths of light interact with a metal the electromagnetic nature of light can cause a reaction in the plasma of electrons that are part of the composition of a metal. This reaction can be considered a plasmon. Many variables come into play when considering a plasmon, the metal, the wavelength of light, the polarization of the light, the geometries involved, and more. Plasmons can resonate and interact in interesting ways and are convenient when one is confronted with the limits imposed by refraction. There is much being done to investigate these phenomenon and many applications are possible with the development of technology based on utilizing the properties of plasmons. Tentative Table of Contents: -Introduction -What is a plasma, and how does it respond to electromagnetic fields? -Quantizing Plasmons. -Surface Plasmons and Polaritons -Spinplasmonics -Research and Applications Thomas Loar In this investigation, methods of fabrication of the chain of particles used to create plasmonic antennas will be reported on. Included in this investigation will be the description of the fundamental limit on the smallest scale which light can be controlled, in other words diffraction. Nanoparticle plasmonic antennas are candidates to beat this limit. Further investigation will include conversion of light into nanoscale localized energy, Plasmon coupling and interference to optimize photon energy localization and transport, and investigation of the various methods of fabrication of the nano-particles such as; induced deposition mask lithography, nano-imprint lithography and multiple resist layer etching, and FIB methods.

4 Marshall Nystrom Quantum Dots in Optics Quantum dots are stable structures within a crystal of some sort in which the excitons (bound electron-hole configurations of neutral charge) are confined in all three spatial dimensions, allowing them to store energy stably in a single location for a significant period of time, with the possible energy levels depending on the size of the dot. Optically, this allows photons to be stored in known locations, which in turn allows much finer manipulation of single photons than is usually possible. This paper shall attempt to give a brief overview of current knowledge regarding excitons and quantum dots with regards to nano- and macro-scale optics. Table of contents: Introduction What is an exciton? A special case of excitons: the quantum dot Uses of quantum dots in nanoscale structures Uses of quantum dots in macroscale and consumer products Conclusion Christian Diaz Hawking Radiation from Ultrashort Laser Pulse Filaments The experiment that this investigation will analyze uses a Refractive Index Perturbation (RIP) to create an optical analogue to a black hole event horizon to create Hawking radiation. Specifically, the RIP is a moving perturbation in a dielectric medium (i.e. fused silica). This RIP effectively stops the laser light in the medium creating the event horizon. This investigation will focus on the concept of a Refractive Index Perturbation in a dielectric medium. Specifically, this project will focus on what a RIP is and how it is formed in the medium, as well as necessary mathematical background info. Outline I: Introduction II: Background i: Perturbation Theory ii: Hawking radiation III: Refractive Index Perturbation i: What they are ii: How they are created iii: How they create an event horizon IV: Conclusions References Belgiorno, F, et al., 2010, Hawking Radiation from Ultrashort Laser Pulse Filaments, Physical Review Letters, v.105. David Lyke Hawking Radiation from Ultrashort Laser Pulse Filaments The experiment described in this paper uses a material known as a Kerr medium to generate Hawking radiation. Ultrashort laser pulses are used to create a refractive index perturbation.

5 These perturbations have event horizons analogous to black holes. This project will focus on Kerr mediums which are non-linear optical mediums. Outline I Introduction II Experiment Background III Kerr Mediums i. What they are ii. How they work iii. How they are used in the experiment IV Conclusions References: Belgiorno, F, et al., 2010, Hawking Radiation from Ultrashort Laser Pulse Filaments, Physical Review Letters, v.105 Joe Rawson Survey of Electron Beam Lithography as it relates to the fabrication of nanoscale devices. Diffraction effects place a fundamental limit on the smallest scales at which light can be directed and controlled. A promising method to attain such small-scale control of light is through the use of nanoparticle arrays. In this paper, I set out to discuss the processes used to fabricate these smallscale structures used in the construction of these arrays and explore the direction Electron Beam Lithography (EBL) technology is currently headed. This topic is of interest to me as I am a Computer Engineering major here at Portland State, and these processes are used to manufacture electronic devices of all types in my field. Outline: 1. Introduction 2. Current overview and background of lithography process. a. Brief background of the processes involved and what they are commonly used for. 3. Electron beam lithography. a. Introduce the Electron Beam Lithography process. b. Discuss the theory behind lithography processes and why the move from light to electr on beams. c. Current limits of the technology, and possible future solutions to those limits. 4. Applications of Electron Beam lithography and how it can be used to manufacture nano -scale devices. 5. Conclusion. Ken Gross F-Theta and telecentric F-Theta lenses are vital to the optical industry. Without them, high speed scribing and processing of materials using light would be severely limited. Allowing the user to input a collimated beam of light to a single point, the combination of galvanometer and F-Theta lens creates a working plane on which the collimated beam is now focused. This beam can be projected (theoretically) anywhere on the plane with very little or no loss of beam quality or spot size. I plan to discuss general theory of F-Theta lenses, including some ray tracing, and if possible, some analysis using an optical design software (ZeMax). I have at my disposal, several F-Theta lenses of differing quality and focal length. I plan to map out the working plane produced by these, by recording the imaged spot size and ellipticity measured by a scanning slit, and how these parameters are affected by input spot size/collimation. Topics of discussion may include: Telecentric vs. non-telecentric F Theta lenses

6 Spherical aberrations How collimation effects focused spot size What effect filling the input aperture has on spot size Theoretical history of F-Theta lenses Different F-Theta lens designs (a single gradient lens vs. 4 separate lenses) Effect of F-theta lens focal length on spot size Effect of wavelength of input light on spot size (why longer wavelength results in larger spot) Carmen Ciobanu Surface plasmon toy-models of black holes Surface plasmons are coherent electron oscillations that propagate along the interface together with an electromagnetic wave. They are the result of special dispersion characteristics of metals and are defined by the shape of the metal-dielectric interface. Surface plasmons live in threedimensional curved space-time, so they become good analogies for many non-trivial space-time entities, such as wormholes and black holes. For example, droplets of dielectric on a metal surface trap the surface plasmons in much the same way a three-dimensional black hole would trap photons. Therefore, electromagnetic toy-models of black holes and wormholes are being created based on surface plasmons. In the absence of an established theory of quantum gravitation, plasmonics provides useful tools in understanding electromagnetic phenomena in curved spacetime. Outline 1. Introduction 2. Description of the research problem posed by the article: Research based on the exchange of ideas between Nano-optics and quantum gravitation theory 3. Scientific work related to the subject of the discussed research Sonic black holes Supersonic fluid flow 4. Details of research article 4.1 Surface plasmons and TM fields theory 4.2 The dispersion law of a surface plasmon 4.3 Description of the experimental set-up and methodology 4.4 Results interpretation; surface plasmons -black holes analogy 5. Conclusion References and sources to be used in the project: 1. Igor I. Smolyaninov, Christopher C. Davis, Surface plasmon toymodels of black holes a nd wormholes, Physical Review B, vol 69, No 20, May W.G. Unruh, Physical Review D, 51, 2827, Albert Polman, Harry A. Atwater, Plasmonics: optics at the nanoscale, Materials Today, 56, January J. R. Sambles, G. W. Bradbery, and F. Yang, "Optical excitation of surface plasmons: an introduction," Contemporary Physics 32, 173, Andres La Rosa, Surface plasmons polaritons at a metal/insulator plane- interface, Lecture notes. 6. Stefan A. Maier, Plasmonics: Fundamentals And Applications, Springer, 2007.