Physics Commons^™

Quantitative, Photocurrent Multidimensional Coherent Spectroscopy, Adam Halaoui

Electronic Theses and Dissertations

Multidimensional coherent spectroscopy (MDCS) is a quickly growing field that has a lot of advantages over more conventional forms of spectroscopy. These advantages all come from the fact that MDCS allows us to get time resolved correlated emission and absorption spectra using very precisely chosen interactions between the density matrix and the excitation laser. MDCS spectra gives the researcher a lot of information that can be extracted purely through qualitative analysis. This is possible because state couplings are entirely separated on the spectra, and once we know how to read the data, we can see how carriers transport in the …

Developing A Data Acquisition System For Use In Cold Neutral Atom Traps, Jonathan E. Fuzaro Alencar

Physics

The rising interest in quantum computing has led to new quantum systems being developed and researched. Among these are trapped neutral atoms which have several desirable features and may be configured and operated on using lasers in an optical lattice. This work describes the development of a new data acquisition system for use in tuning lasers near the precise hyperfine transition frequencies of Rb 87 atoms, a crucial step in the functionality of a neutral atom trap. This improves on previous implementations that were deprecated and limited in laser frequency sweep range. Integration into the experiment was accomplished using an …

The Complex Propagation Of Light Explained Visually: How To Make A Hologram, Bruno Ray Becher

Senior Projects Spring 2021

The complexity of light’s wave nature is shown in the paths that light takes. In this project I will show several useful ways to imagine and predict how light will travel from one place to another. Once light is produced it does not immediately fill a room, instead it undulates through free space as if the space itself was a fluid. Once we understand the way light flows and interacts with its environment not only can we predict and control its shape with a hologram, but also discover clues which give secrets about where the light has been. Telescopes and …

An Overview Of Lasers And Their Applications, Luis Cristian Giovanni Guerrero

Physics

This paper is an overview of lasers and their applications. The fundamentals of laser operation are covered as well as the various applications of advanced laser systems. The primary focus is to highlight some of the technological advancements made possible by lasers in the last half-century.

The Design Of A Continuous Wave Molecular Nitrogen Stimulated Raman Laser In The Visible Spectrum, Timothy J. Bate

Theses and Dissertations

Hollow-core photonic crystal fibers (HCPCFs) shows promise as a hybrid laser with higher nonlinear process limits and small beam size over long gain lengths. This work focuses on the design of a CW molecular nitrogen (N₂) stimulated Raman laser. N₂ offers Raman gains scaling up to 900 amg, scaling higher than H₂. The cavity experiment showed the need to include Rayleigh scattering in the high pressure required for N₂ Raman lasing. Even at relatively low pressure ssuch as 1,500 psi, high conversion percentages should be found if the fiber length is chosen based on …

Structuring Light For Investigating Optical Vortices, Andrew Voitiv, Mark Siemens

DU Undergraduate Research Journal Archive

Vortices are well known in our world: tornadoes, hurricanes, and quickly stirred iced tea all demonstrate the vortex phenomenon. In addition to these classical fluids, vortices exist in laser light. While classical fluid vortex dynamics is one of the oldest studied physics problems, the study of optical vortices is only a few decades old. Paralleling the community’s curiosity of quantized vortices in quantum fluids, such as super fluid helium and Bose-Einstein condensate, there is immense interest in the study of optical vortices. In this article, we cover the basic theory of structuring light to generate optical vortices and then discuss …

Excitable Interplay Between Lasing Quantum Dot States, Michael Dillane, I. Dubinkin, N. Fedorov, T. Erneux, David Goulding, B. Kelleher, E.A. Viktorov

Cappa Publications

The optically injected semiconductor laser system has proven to be an excellent source of experimental nonlinear dynamics, particularly regarding the generation of excitable pulses. Typically for low-injection strengths, these pulses are the result of a small above-threshold perturbation of a stable steady state, the underlying physics is well described by the Adler phase equation, and each laser intensity pulse is accompanied by a 2π phase rotation. In this article, we show how, with a dual-state quantum dot laser, a variation of type I excitability is possible that cannot be described by the Adler model. The laser is operated so that …

Monolayer Doping Of Silicon-Germanium Alloys: A Balancing Act Between Phosphorus Incorporation And Strain Relaxation, Noel Kennedy, Ray Duffy, Gioele Mirabelli, Luke Eaton, Nikolay Petkov, Justin D. Holmes, Chris Hatem, Lee Walsh, Brenda Long

Cappa Publications

This paper presents the application of monolayer doping (MLD) to silicon-germanium (SiGe). This study was carried out for phosphorus dopants on wafers of epitaxially grown thin films of strained SiGe on silicon with varying concentrations of Ge (18%, 30%, and 60%). The challenge presented here is achieving dopant incorporation while minimizing strain relaxation. The impact of high temperature annealing on the formation of defects due to strain relaxation of these layers was qualitatively monitored by cross-sectional transmission electron microscopy and atomic force microscopy prior to choosing an anneal temperature for the MLD drive-in. Though the bulk SiGe wafers provided are …

Slow Light With Interleaved P-N Junction To Enhance Performance Of Integrated Mach-Zehnder Silicon Modulators, Marco Passoni, Dario Gerace, Liam O'Faolain, Lucio Claudio Andreani

Cappa Publications

Slow light is a very important concept in nanophotonics, especially in the context of photonic crystals. In this work, we apply our previous design of band-edge slow light in silicon waveguide gratings [M. Passoni et al, Opt. Express 26, 8470 (2018)] to Mach-Zehnder modulators based on the plasma dispersion effect. The key idea is to employ an interleaved p-n junction with the same periodicity as the grating, in order to achieve optimal matching between the electromagnetic field profile and the depletion regions of the p-n junction. The resulting modulation efficiency is strongly improved as compared to common modulators based on …

Single Metalens For Generating Polarization And Phase Singularities Leading To A Reverse Flow Of Energy, Victor V. Kotlyar, Anton G. Nalimov, Sergey S. Stafeev, Liam O'Faolain

Cappa Publications

Using Jones matrices and vectors, we show that a metasurface-based optical element composed of a set of subwavelength diffraction gratings, whose anisotropic transmittance is described by a matrix of polarization rotation by angle m, where is the polar angle, generate an mth order azimuthally or radially polarized beam, when illuminated by linearly polarized light, or an optical vortex with topological charge m, when illuminated by circularly polarized light. Such a converter performs a spin–orbit transformation, acting similarly to a liquid-crystal half-wave plate. Using the FDTD-aided numerical simulation, we show that uniform linearly or circularly polarized light passing through the …

Subwavelength Grating-Based Spiral Metalens For Tight Focusing Of Laser Light, Victor V. Kotlyar, Sergey S. Stafeev, Anton G. Nalimov, Liam O'Faolain

Cappa Publications

In this paper, we investigate a 16-sector spiral metalens fabricated on a thin film (130 nm) of amorphous silicon, consisting of a set of subwavelength binary diffractive gratings and with a numerical aperture that is close to unity. The metalens converts linearly polarized incident light into an azimuthally polarized optical vortex and focuses it at a distance approximately equal to the wavelength of the incident light, k ¼ 633 nm. Using a scanning near-field optical microscope, it is shown experimentally that the metalens forms an elliptical focal spot with diameters smaller than the diffraction limit: FWHMx ¼ 0.32k (60.03k) and …

Rotation Of Two-Petal Laser Beams In The Near Field Of A Spiral Microaxicon, S. S. Stafeev, Liam O'Faolain, M. V. Kotlyar

Cappa Publications

Using a spiral microaxicon with the topological charge 2 and NA = 0.6 operating at a 532-nm wavelength and fabricated by electron-beam lithography, we experimentally demonstrate the rotation of a two-petal laser beam in the near field (several micrometers away from the axicon surface). The estimated rotation rate is 55 °/mm and linearly dependent on the on-axis distance, with the theoretical rotation rate being 53 °/mm. The experimentally measured rotation rate is found to be linear and coincident with the simulation results only on the on-axis segment from 1.5 to 3 mm. The experimentally measured rotation rate is 66 °/mm …

Assembling And Characterizing The Efficiency Of An Injection Locked Laser System For Cold Neutral Atom Optical Traps, Alexandra Papa Crawford

Physics

Creating a quantum computer requires a system of particles that can be well-controlled to achieve quantum operations. We need a large array of these particles – called qubits – with long coherence times, which can be initialized, operated on by single and two qubit gates, and read out. For neutral atoms, the qubit states are stable ground states that interact minimally with the environment, leading to long coherence times. Experimentally, the qubits are manipulated using carefully timed laser beam pulses with controlled frequency and intensity, but the outstanding issue for optically trapping cold atoms is finding a light pattern that …

Tunable Optical Buffer Through An Analogue To Electro-Magnetically Induced Transparency In Coupled Photonic Crystal Cavities, Changyu Hu, Sebastian A. Schulz, Alexandros A. Liles, Liam O'Faolain

Cappa Publications

Tunable on-chip optical delay has long been a key target for the research community, as it is the enabling technology behind delay lines, signal re-timing and other applications vital to optical signal processing. To date the field has been limited by high optical losses associated with slow light or delay structures. Here, we present a novel tunable delay line, based on a coupled cavity system exhibiting an Electromagnetically Induced Transparency-like transmission spectrum, with record low loss, around 15dB/ns. By tuning a single cavity the delay of the complete structure can be tuned over 120ps, with the maximum delay approaching 300ps.

Analysis Of The Red And Green Optical Absorption Spectrum Of Gas Phase Ammonia, Nikolai F. Zobov, Phillip A. Coles, Roman I. Ovsyannikov, Aleksandra A. Kyuberis, Robert J. Hargreaves, Peter F. Bernath, Jonathan Tennyson, Sergei N. Yurchenko, Oleg L. Polyansky

Chemistry & Biochemistry Faculty Publications

Room temperature NH₃ absorption spectra recorded at the Kitt Peak National Solar Observatory in 1980 are analyzed. The spectra cover two regions in the visible: 15,200 - 15,700 cm^-1 and 17,950 - 18,250 cm^-1. These high overtone rotation-vibration spectra are analyzed using both combination differences and variational line lists. Two variational line lists were computed using the TROVE nuclear motion program: one is based on an ab initio potential energy surface (PES) while the other used a semi-empirical PES. Ab initio dipole moment surfaces are used in both cases. 95 energy levels with J = 1 …

Studies In Mesoscopics And Quantum Microscopies, Zhenghao Ding, Gabriel C. Spalding

Honors Projects

This thesis begins with a foundational section on quantum optics. The single-photon detectors used in the first chapter were obtained through the Advanced Laboratory Physics Association (ALPhA), which brokered reduced cost for educational use, and the aim of the single-photon work presented in Chapter 1 is to develop modules for use in Illinois Wesleyan's instructional labs beyond the first year of university. Along with the American Association of Physics Teachers, ALPhA encourages capstone-level work, such as Chapter 1 of this honors thesis, which is explicitly designed to play the role of passing on, to a next generation of physics majors, …

Using An Atomic Molecular Optics Laboratory For Undergraduate Research And Mentoring Of Physics Students In Georgia, Matthew P. Dallas

Georgia College Student Research Events

Using an Atomic Molecular Optics Laboratory for Undergraduate Research and Mentoring of Physics Students in Georgia

An Atomic and Molecular Optical (AMO) Physics research lab is an excellent tool to train and mentor undergraduate students in advanced laboratory techniques. Students gain valuable basic experience in experimental designs, data acquisition techniques, working with high precision optical equipment, building electronics, and working in the machine shop. The current project is building and testing an enclosure for the diode laser to reduce sound and vibrational interference. In addition, we are developing and evaluating a new, more compact laser cavity which is 3d printed. …

Nonlocal Polarization Interferometry And Entanglement Detection, Brian P. Williams

Doctoral Dissertations

At present, quantum entanglement is a resource, distributed to enable a variety of quantum information applications such as quantum key distribution, superdense coding, and teleportation. Necessarily, the distribution and characterization of entanglement is fundamental to its application. This dissertation details three research efforts to enable nonlocal entanglement detection, distribution, and characterization. Foremost of these efforts, we present the theory and demonstration of a nonlocal polarization interferometer capable of detecting entanglement and identifying Bell states statistically. This is possible due to the interferometer’s unique correlation dependence on the anti-diagonal elements of the density matrix, which have distinct bounds for separable states …

Experimental Realization Of Slowly Rotating Modes Of Light, Fangzhao A. An

HMC Senior Theses

Beams of light can carry spin and orbital angular momentum. Spin angular momentum describes how the direction of the electric field rotates about the propagation axis, while orbital angular momentum describes the rotation of the field amplitude pattern. These concepts are well understood for monochromatic beams, but previous theoretical studies have constructed polychromatic superpositions where the connection between angular momentum and rotation of the electric field becomes much less clear. These states are superpositions of two states of light carrying opposite signs of angular momentum and slightly detuned frequencies. They rotate at the typically small detuning frequency and thus we …

Forcing Mutual Coherence In Diode Laser Stacks, Jonathan R. Wurtz

Honors Theses and Capstones

This paper will discuss both theoretical and experimental attempts to improve the spatial beam quality of diode laser stacks using an external optical system. An overview and derivation of the mathematics of both the optical system and diode lasers will be discussed. The experimental setup will be presented, as well as the fundamental theoretical and experimental results that suggest the external optical system used for this thesis fails to improve the beam quality of a diode laser stack.

Computational Renormalization Scheme For Quantum Field Theories, Rainer Grobe, Qichang Su, R E. Wagner

Faculty publications – Physics

We propose an alternative technique for numerically renormalizing quantum field theories based on their Hamiltonian formulation. This method is nonperturbative in nature and, therefore, exact to all orders. It does not require any correlation functions or Feynman diagrams. We illustrate this method for a model Yukawa-like theory describing the interaction of electrons and positrons with model photons in one spatial dimension. We show that, after mass renormalization of the fermionic and bosonic single-particle states, all other states in the Fock space have finite energies, which are independent of the momentum cutoff.

Optical Switching With Cold Atoms, Andrew Dawes

Andrew M C Dawes

A Viewpoint on: Efficient All-Optical Switching Using Slow Light within a Hollow Fiber M. Bajcsy, S. Hofferberth, V. Balic, T. Peyronel, M. Hafezi, A. S. Zibrov, V. Vuletic, and M. D. Lukin Phys. Rev. Lett. 102, 203902 (2009) – Published May 18, 2009

Enhancement Of Electron-Positron Pair Creation Due To Transient Excitation Of Field-Induced Bound States, M Jiang, Q Z. Lv, Z M. Sheng, Rainer Grobe, Qichang Su

Faculty publications – Physics

We study the creation of electron-positron pairs induced by two spatially separated electric fields that vary periodically in time. The results are based on large-scale computer simulations of the time-dependent Dirac equation in reduced spatial dimensions. When the separation of the fields is very large, the pair creation is caused by multiphoton transitions and mainly determined by the frequency of the fields. However, for small spatial separations a coherence effect can be observed that can enhance or reduce the particle yield compared to the case of two infinitely separated fields. If the travel time for a created electron or positron …

Pair Creation For Bosons In Electric And Magnetic Fields, Q Z. Lv, A C. Su, M Jiang, Rainer Grobe, Qichang Su

Faculty publications – Physics

By solving the quantum field theoretical version of the Klein-Gordon equation numerically, we study the creation process for charged boson-antiboson pairs in static electric and magnetic fields. The fields are perpendicular to each other and spatially localized along the same direction, which permits us to study the crucial impact of the magnetic field's spatial extension on dynamics. If its width is comparable to that of the electric field, we find a magnetically induced Lorentz suppression of the pair-creation process. When the width is increased such that the created bosons can revisit the interaction region, we find a region of exponential …

Suppression Of Pair Creation Due To A Steady Magnetic Field, W Su, M Jiang, Z Q. Lv, Rainer Grobe, Qichang Su

Faculty publications – Physics

We investigate the electron-positron pair creation process in a supercritical static electric field in the presence of a static magnetic field that is perpendicular. If both fields vary spatially in one direction the dynamics can be reduced to a set of one-dimensional systems. Using a generalized computational quantum field theoretical procedure, we calculate the time dependence of the spatial density for the created electrons. In the presence of the magnetic field, a significant amount of suppression of pair creation is observed in the simulations and confirmed by an analytical analysis for the limits of short-range fields and long interaction times. …

Microwave Optics Research, Allen Andersen, Todd Lines, Josh Barney

Allen Andersen

The BYU-Idaho Physics Department x-band microwave optics equipment was originally intended for use in classroom demonstrations. I evaluated this equipment for use in research. I designed and built additional equipment needed in order to perform attenuation and other experiments then used it to conduct research on the transmission properties of paper and other substances. The new equipment allowed me to create a standard experimental procedure, take reasonably accurate measurements, and reduce undesired standing wave effects. Mathematical and experimental analysis was done to determine the necessary parameters of the new equipment. The new apparatus is comparable to setups featured in published …

Pair Creation Enhancement Due To Combined External Fields, M Jiang, W Su, Z Q. Lv, X Lu, Y J. Li, Rainer Grobe, Qichang Su

Faculty publications – Physics

We study the creation of electron-positron pairs from the vacuum induced by a combination of a static electric field and an alternating field. We find that the overall pair production can be increased by two orders of magnitude compared to the yields associated with each field individually. We examine the interesting case where both fields are spatially localized, permitting us to examine the time evolution of the spatial density for the created particle pairs. We find that there are a variety of competing mechanisms that contribute to the total yield.

Local And Nonlocal Spatial Densities In Quantum Field Theory, R E. Wagner, M R. Ware, E V. Stefanovich, Qichang Su, Rainer Grobe

Faculty publications – Physics

We use a one-dimensional model system to compare the predictions of two different yardsticks to compute the position of a particle from its quantum field theoretical state. Based on the first yardstick (defined by the Newton-Wigner position operator), the spatial density can be arbitrarily narrow, and its time evolution is superluminal for short time intervals. Furthermore, two spatially distant particles might be able to interact with each other outside the light cone, which is manifested by an asymmetric spreading of the spatial density. The second yardstick (defined by the quantum field operator) does not permit localized states, and the time …

Causality And Relativistic Localization In One-Dimensional Hamiltonians, R E. Wagner, B T. Shields, M R. Ware, Qichang Su, Rainer Grobe

Faculty publications – Physics

We compare the relativistic time evolution of an initially localized quantum particle obtained from the relativistic Schrodinger, the Klein-Gordon and the Dirac equations. By computing the amount of the spatial probability density that evolves outside the light cone we quantify the amount of causality violation for the relativistic Schrodinger Hamiltonian. We comment on the relationship between quantum field theoretical transition amplitudes, commutators of the fields and their bilinear combinations outside the light cone as indicators of a possible causality violation. We point out the relevance of the relativistic localization problem to this discussion and comment on ideas about the supposed …

Electron-Positron Pair Creation Induced By Quantum-Mechanical Tunneling, M Jiang, W Su, X Lu, Z M. Sheng, Y T. Li, J Zhang, Rainer Grobe, Qichang Su

Faculty publications – Physics

We study the creation of electron-positron pairs from the vacuum induced by two spatially displaced static electric fields. The strength and spatial width of each localized field is less than required for pair creation. If, however, the separation between the fields is less than the quantum-mechanical tunneling length associated with the corresponding quantum scattering system, the system produces a steady flux of electron-positron pairs. We compute the time dependence of the pair-creation probability by solving the Dirac equation numerically for various external field sequences. For the special case of two very narrow fields we provide an analytical expression for the …