Solid-state laser system for laser cooling of Sodium

We demonstrate a frequency-stabilized, all-solid laser source at 589 nm with up to 800 mW output power. The laser relies on sum-frequency generation from two laser sources at 1064 nm and 1319 nm through a PPKTP crystal in a doubly-resonant cavity. We obtain conversion efficiency as high as 2 W/W^2 after optimization of the cavity parameters. The output wavelength is tunable over 60 GHz, which is sufficient to lock on the Sodium D2 line. The robustness, beam quality, spectral narrowness and tunability of our source make it an alternative to dye lasers for atomic physics experiments with Sodium atoms

Time-Reversal of Nonlinear Waves - Applicability and Limitations

Time-reversal (TR) refocusing of waves is one of fundamental principles in wave physics. Using the TR approach, "Time-reversal mirrors" can physically create a time-reversed wave that exactly refocus back, in space and time, to its original source regardless of the complexity of the medium as if time were going backwards. Lately, laboratory experiments proved that this approach can be applied not only in acoustics and electromagnetism but also in the field of linear and nonlinear water waves. Studying the range of validity and limitations of the TR approach may determine and quantify its range of applicability in hydrodynamics. In this context, we report a numerical study of hydrodynamic TR using a uni-directional numerical wave tank, implemented by the nonlinear high-order spectral method, known to accurately model the physical processes at play, beyond physical laboratory restrictions. The applicability of the TR approach is assessed over a variety of hydrodynamic localized and pulsating structures' configurations, pointing out the importance of high-order dispersive and particularly nonlinear effects in the refocusing of hydrodynamic stationary envelope solitons and breathers. We expect that the results may motivate similar experiments in other nonlinear dispersive media and encourage several applications with particular emphasis on the field of ocean engineering.Comment: 14 pages, 17 figures ; accepted for publication in Phys. Rev. Fluid

Atomic masses of intermediate-mass neutron-deficient nuclei with relative uncertainty down to 35-ppb via multireflection time-of-flight mass spectrograph

High-precision mass measurements of $^{63}$Cu, $^{64-66}$Zn, $^{65}$Ga, $^{65-67}$Ge, $^{67}$As, $^{78,81}$Br, $^{80}$Rb, and $^{79}$Sr were performed utilizing a multireflection time-of-flight mass spectrograph combined with the gas-filled recoil ion separator GARIS-II. In the case of $^{65}$Ga, a mass uncertainty of 2.1 keV, corresponding to a relative precision of $\delta m / m = 3.5\times10^{-8}$, was obtained and the mass value is in excellent agreement with the 2016 Atomic Mass Evaluation. For $^{67}$Ge and $^{81}$Br, where masses were previously deduced through indirect measurements, discrepancies with literature values were found. The feasibility of using this device for mass measurements of nuclides more neutron-deficient side, which have significant impact on the $rp$-process pathway, is discussed.Comment: 15 pages, 6 figures, 1 tabl

Interference effects in second-harmonic generation within an optical cavity

An experiment is described that investigates certain interference effects for second-harmonic generation within a resonant cavity. By employing a noncollinear geometry, the phases of two fundamental beams from a frequency-stabilized dye laser can be controlled unrestricted by the boundary conditions imposed in an optical cavity containing a KDP crystal and resonant at the second harmonic. The fundamental beams are either traveling or standing waves and generate either one or two coherent sources of ultraviolet radiation within the cavity. The experiment demonstrates explicitly the dependence of second-harmonic phase on the fundamental phases and the dependence of coupling efficiency on the overlap of the harmonic polarization wave with the cavity-mode function. The measurements agree well with a simple theory

Real-time simulation of interferometric gravitational wave detectors involving moving mirrors

A method of real-time dynamical simulation for laser interferometric gravitational wave detectors is presented. The method is based on a digital filtering approach and a number of important physical points understood by a step-by-step investigation of two-mirror cavities, a three-mirror coupled cavity, and a full-length power-recycled interferometer with mirrors having longitudinal motion. The final analytical representation used for the fast simulation of a full-length power-recycled interferometer is analogous to a two-mirror dynamical cavity with time-dependent reflectivities, when intracavity fields of the interferometer are expressed together in a state-vector representation. A detailed discussion establishes the relationships among physical effects pertaining to field evolution in two-mirror cavities and coupled cavities or to the full interferometer

Quantum and classical localisation and the Manhattan lattice

We consider a network model, embedded on the Manhattan lattice, of a quantum localisation problem belonging to symmetry class C. This arises in the context of quasiparticle dynamics in disordered spin-singlet superconductors which are invariant under spin rotations but not under time reversal. A mapping exists between problems belonging to this symmetry class and certain classical random walks which are self-avoiding and have attractive interactions; we exploit this equivalence, using a study of the classical random walks to gain information about the corresponding quantum problem. In a field-theoretic approach, we show that the interactions may flow to one of two possible strong coupling regimes separated by a transition: however, using Monte Carlo simulations we show that the walks are in fact always compact two-dimensional objects with a well-defined one-dimensional surface, indicating that the corresponding quantum system is localised.Comment: 11 pages, 8 figure

MODELING AND FABRICATION OF LIGHTWEIGHT, DEFORMABLE MIRRORS SUBJECTED TO DISCRETE LOADING

The push towards larger diameter space telescope mirrors has caused the space industry to look at lightweight, deformable alternatives to the traditional monolithic mirror. One possible solution to the dilemma is to use the piezoelectric properties of certain materials to create a lightweight, deformable mirror. Current piezoelectric deformable mirror designs use individual actuators, creating an immensely complex system as the mirrors increase in size. The objective of this thesis is to aid in the design and development of lightweight, deformable mirrors for use in space based telescopes. Two topics are considered to aid this development. A doubly curved, lightweight, bimorph mirror is investigated. The fabrication method entails forming a thin film piezoelectric polymer into a doubly curved shape using a specially designed forming machine. The second topic entails the finite element modeling of a composite mirror substrate with a piezoceramic actuator backing. The model is generated using a meshing program designed to generate off-centered spot loads of electric potential. These spot loads simulate the actuation due to an electron gun. The effects of spot location and size on mirror deformation are examined

Pynchon’s Against the Day: Bilocation, Duplication, and Differential Repetition

In Against the Day, Pynchon is obsessed with twoness, double worlds, as well as dual realities, and like Deleuze’s concept of repetition, these duplications and twinships are not merely repetition of the same, rather they allow for creativity, reinvention, and becoming. Pynchon’s duplication of fictional and spectral characters intends to critique the notion of identity as does Deleuzian concept of repetition. Not attached to the representational concept of identity as the recurrence of the same, Pynchon’s duplications decenter the transcendental concept in favor of a perpetual becoming and reproduces difference and singularity. Like Deleuze, Pynchon eschews an identity that is always guaranteed, and shows that the repetition of an object or a subject is not the recurrence of the original self-identical object or person. Moreover, Iceland spar, the mystifying calcite, with its doubling effect provides the reader with a view of a world beyond the ordinary, actual world, which is quite similar to what Pynchon’s novel does per se

Ferroelectric Phase Transitions in Ultra-thin Films of BaTiO3

We present molecular dynamics simulations of a realistic model of an ultrathin film of BaTiO$_3$ sandwiched between short-circuited electrodes to determine and understand effects of film thickness, epitaxial strain and the nature of electrodes on its ferroelectric phase transitions as a function of temperature. We determine a full epitaxial strain-temperature phase diagram in the presence of perfect electrodes. Even with the vanishing depolarization field, we find that ferroelectric phase transitions to states with in-plane and out-of-plane components of polarization exhibit dependence on thickness; it arises from the interactions of local dipoles with their electrostatic images in the presence of electrodes. Secondly, in the presence of relatively bad metal electrodes which only partly compensate the surface charges and depolarization field, a qualitatively different phase with stripe-like domains is stabilized at low temperature