Effect of energy interlock on possible beam losses in the Booster to Storage Ring transfer line

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Ultrafast terahertz spectroscopy and control of collective modes in semiconductors

In this dissertation we applied methods of ultrafast terahertz (THz) spectroscopy to study several aspects of semiconductor physics and in particular of collective mode excitations in semiconductors. We detect and analyze THz radiation emitted by these collective modes to reveal the underlying physics of many-body interactions. We review a design, implementation and characterization of our ultrafast terahertz (THz) time-domain spectroscopy setup, with additional features of mid-infrared tunability and coherent as well as incoherent detection capabilities. Temperature characterization of the collective plasmon excitation in indium antimonide (InSb) is presented to reveal the importance of non-parabolicity corrections in quantitative description. We also obtain electronic mobility from the radiation signals, which, once corrected for ultrafast scattering mechanisms, is in good agreement with DC Hall mobility measurements. Exhibited sensitivity to non-parabolicity and electronic mobility is applicable to non-contact characterization of electronic transport in nanostructures. As a first goal of this work, we have addressed the possibility of an all-optical control of the electronic properties of condensed matter systems on an ultrafast time scale. Using femtosecond pulses we have demonstrated an ability to impose a nearly 20% blue-shift of the plasma frequency in InSb. Preliminary investigations of control of the electron dynamics using third-order nonlinearity were also carried out in solid state and gaseous media. In particular, we have experimentally verified the THz coherent control in air-breakdown plasmas and have demonstrated the ability to induce quantum-interference current control in indium arsenide crystals. As a second focus of this dissertation, we have addressed manipulation of the plasmon modes in condensed matter systems. After development of the analytical model of radiation from spatially extended longitudinal modes, we have applied it to analysis of two experiments. In first, we established the ability to control plasmon modes in InSb by means of a plasmonic one dimensional cavity. By control of the cavity geometry, we shifted the plasmon mode into the regime where non-local electron-electron interaction is enforced. We observed the consequential Landau damping of the collective mode, in good agreement with the predictions made within the random-phase approximation. In the second experiment we have invoked plasmon confinement in all three dimensions via a nanowire geometry. We observed enhancement of terahertz emission which we attributed to leaky modes of the waveguide. We attributed this emission to the low-energy acoustic surface plasmon mode of the nanowire, which was also supported by our numerical modeling results and independent DC electronic measurements

Useful formulas for non-magnetized electron cooling

Recent success of Low Energy RHIC Electron Cooler (LEReC) opened a road for development of high energy electron coolers based on non-magnetized electron bunches accelerated by RF cavities. Electrons in such coolers can have velocity distribution with various unequal horizontal, vertical and longitudinal velocity spreads. In this paper we revisit a formula of friction force in non-magnetized cooling and derive a number of useful expressions for different limiting cases

Paraxial Theory of Direct Electro-Optic Sampling of the Quantum Vacuum

Direct detection of vacuum fluctuations and analysis of sub-cycle quantum properties of the electric field are explored by a paraxial quantum theory of ultrafast electro-optic sampling. The feasibility of such experiments is demonstrated by realistic calculations adopting a thin ZnTe electro-optic crystal and stable few-femtosecond laser pulses. We show that nonlinear mixing of a short near-infrared probe pulse with multi-terahertz vacuum field modes leads to an increase of the signal variance with respect to the shot noise level. The vacuum contribution increases significantly for appropriate length of the nonlinear crystal, short probe pulse durations, tight focusing, and sufficiently large number of photons per probe pulse. If the vacuum input is squeezed, the signal variance depends on the probe delay. Temporal positions with noise level below the pure vacuum may be traced with a sub-cycle accuracy.Comment: 10 pages, 6 figure

Spectra of ultrabroadband squeezed pulses and the finite-time Unruh-Davies effect

We study spectral properties of quantum radiation of ultimately short duration. In particular, we introduce a continuous multimode squeezing operator for the description of subcycle pulses of entangled photons generated by a coherent-field driving in a thin nonlinear crystal with second order susceptibility. We find the ultrabroadband spectra of the emitted quantum radiation perturbatively in the strength of the driving field. These spectra can be related to the spectra expected in an Unruh-Davies experiment with a finite time of acceleration. In the time domain, we describe the corresponding behavior of the normally ordered electric field variance.Comment: 11 pages, 5 figure

Direct measurement of the Husimi-Q function of the electric-field in the time-domain

We develop the theoretical tools necessary to promote electro-optic sampling to a time-domain quantum tomography technique. Our proposed framework implements detection of the time evolution of both the electric-field of a propagating electromagnetic wave and its Hilbert transform (quadrature). Direct detection of either quadrature is not strictly possible in the time-domain, detection efficiency approaching zero when an exact mode-matching to either quadrature is reached. As all real signals have a limited bandwidth, we can trace out the irrelevant sampling bandwidth to optimize the detection efficiency while preserving quantum information of the relevant signal. Through the developed understanding of the mode structure of the amplitude and Hilbert transform quadratures, we propose multiplexing and mode-matching operations on the gating function to extract full quantum information on both quantities, simultaneously. The proposed methology is poised to open a novel path toward quantum state tomography and quantum spectroscopy directly in the time domain.Comment: 9 pages, 7 figure

Nonlinear acousto-magneto-plasmonics

We review the recent progress in experimental and theoretical research of interactions between the acoustic, magnetic and plasmonic transients in hybrid metal-ferromagnet multilayer structures excited by ultrashort laser pulses. The main focus is on understanding the nonlinear aspects of the acoustic dynamics in materials as well as the peculiarities in the nonlinear optical and magneto-optical response. For example, the nonlinear optical detection is illustrated in details by probing the static magneto-optical second harmonic generation in gold-cobalt-silver trilayer structures in Kretschmann geometry. Furthermore, we show experimentally how the nonlinear reshaping of giant ultrashort acoustic pulses propagating in gold can be quantified by time-resolved plasmonic interferometry and how these ultrashort optical pulses dynamically modulate the optical nonlinearities. The effective medium approximation for the optical properties of hybrid multilayers facilitates the understanding of novel optical detection techniques. In the discussion we highlight recent works on the nonlinear magneto-elastic interactions, and strain-induced effects in semiconductor quantum dots.Comment: 30 pages, 12 figures, to be published as a Topical Review in the Journal of Optic

Precise Determination of Minimum Achievable Temperature for Solid-State Optical Refrigeration

We measure the minimum achievable temperature (MAT) as a function of excitation wavelength in anti-Stokes fluorescence cooling of high purity Yb3+-doped LiYF4 (Yb:YLF) crystal. Such measurements were obtained by developing a sensitive noncontact thermometry that is based on a two-band differential luminescence spectroscopy using balanced photo-detectors. These measurements are in excellent agreement with the prediction of the laser cooling model and identify MAT of 110 K at 1020 nm, corresponding to E4-E5 Stark manifold transition in Yb:YLF crystal.Comment: 10 pages, 6 figure