Injection Locking of a Trapped-Ion Phonon Laser

We report on injection locking of optically excited mechanical oscillations of a single, trapped ion. The injection locking dynamics are studied by analyzing the oscillator spectrum with a spatially selective Fourier transform technique and the oscillator phase with stroboscopic imaging. In both cases we find excellent agreement with theory inside and outside the locking range. We attain injection locking with forces as low as 5(1)×10^(-24)  N so this system appears promising for the detection of ultraweak oscillating forces

Thin-disk laser pump schemes for large number of passes and moderate pump source quality

Novel thin-disk laser pump layouts are proposed yielding an increased number of passes for a given pump module size and pump source quality. These novel layouts result from a general scheme which bases on merging two simpler pump optics arrangements. Some peculiar examples can be realized by adapting standard commercially available pump optics simply by intro ducing an additional mirror-pair. More pump passes yield better efficiency, opening the way for usage of active materials with low absorption. In a standard multi-pass pump design, scaling of the number of beam passes brings ab out an increase of the overall size of the optical arrangement or an increase of the pump source quality requirements. Such increases are minimized in our scheme, making them eligible for industrial applicationsComment: 16 pages, 9 figure

Observing the Profile of an Atom Laser Beam

We report on an investigation of the beam profile of an atom laser extracted from a magnetically trapped $^{87}$Rb Bose-Einstein condensate. The transverse momentum distribution is magnified by a curved mirror for matter waves and a momentum resolution of 1/60 of a photon recoil is obtained. We find the transverse momentum distribution to be determined by the mean-field potential of the residing condensate, which leads to a non-smooth transverse density distribution. Our experimental data are compared with a full 3D simulation of the output coupling process and we find good agreement.Comment: 4 pages, 4 figure

Selective excitation of metastable atomic states by femto- and attosecond laser pulses

The possibility of achieving highly selective excitation of low metastable states of hydrogen and helium atoms by using short laser pulses with reasonable parameters is demonstrated theoretically. Interactions of atoms with the laser field are studied by solving the close-coupling equations without discretization. The parameters of laser pulses are calculated using different kinds of optimization procedures. For the excitation durations of hundreds of femtoseconds direct optimization of the parameters of one and two laser pulses with Gaussian envelopes is used to introduce a number of simple schemes of selective excitation. To treat the case of shorter excitation durations, optimal control theory is used and the calculated optimal fields are approximated by sequences of pulses with reasonable shapes. A new way to achieve selective excitation of metastable atomic states by using sequences of attosecond pulses is introduced.Comment: To be published in Phys. Rev. A, 10 pages, 3 figure

Cavity Enhanced Optical Vernier Spectroscopy, Broad Band, High Resolution, High Sensitivity

A femtosecond frequency comb provides a vast number of equidistantly spaced narrow band laser modes that can be simultaneously tuned and frequency calibrated with 15 digits accuracy. Our Vernier spectrometer utilizes all of theses modes in a massively parallel manner to rapidly record both absorption and dispersion spectra with a sensitivity that is provided by a high finesse broad band optical resonator and a resolution that is only limited by the frequency comb line width while keeping the required setup simple.Comment: 11 pages, 3 figures, submitted to PR

An ion-trap phonon laser

Cooling of atoms and ions using a red-detuned laser has had a profound impact on science and technology. In this work simultaneous laser cooling and blue-detuned laser pumping of a Mg+ ion in a Paul trap is studied. Blue-detuned pumping is conventionally referred to as the heating regime, and in early work, remarkably complex behaviors (bistability and limit cycles) have been associated with this regime. These behaviors have so far not been fully explained. Here, it is shown that blue-detuned pumping, as opposed to heating, causes stimulated emission of center-of-mass phonons, leading to coherent oscillatory motion of the ion in analogy with a laser. Mechanical amplification is calculated as well as the threshold pumping condition for oscillation. A single ion in a linear radio-frequency trap is studied to verify these predictions. Blue-detuned pumping of the magnesium D2 transition at 279.6 nm provides amplification along the long axis of the ion trap so as to excite only axial oscillations. A slightly off-axis, red-detuned beam cools the center-of-mass motion to approximately 1 mK

Modeling of mode-locking in a laser with spatially separate gain media

We present a novel laser mode-locking scheme and discuss its unusual properties and feasibility using a theoretical model. A large set of single-frequency continuous-wave lasers oscillate by amplification in spatially separated gain media. They are mutually phase-locked by nonlinear feedback from a common saturable absorber. As a result, ultra short pulses are generated. The new scheme offers three significant benefits: the light that is amplified in each medium is continuous wave, thereby avoiding issues related to group velocity dispersion and nonlinear effects that can perturb the pulse shape. The set of frequencies on which the laser oscillates, and therefore the pulse repetition rate, is controlled by the geometry of resonator-internal optical elements, not by the cavity length. Finally, the bandwidth of the laser can be controlled by switching gain modules on and off. This scheme offers a route to mode-locked lasers with high average output power, repetition rates that can be scaled into the THz range, and a bandwidth that can be dynamically controlled. The approach is particularly suited for implementation using semiconductor diode laser arrays.Comment: 13 pages, 5 figures, submitted to Optics Expres

Основні закономірності зародження і росту втомних тріщин в алюмінієвих пластинах із зміцненими отворами

The method of modeling stress-strain state for holes burnishing using FEM has been analyzed. A series of fatigue tests were carried out using plates containing plain holes and cold expanded holes in aluminium For various diameters of holes and cold expansion degree there exists a certain correlation between the stress range or maximum stress on the edge of hole on the entrance face of plate and lifetime of fatigue crack initiation

Two-Loop Self-Energy Corrections to the Fine-Structure

We investigate two-loop higher-order binding corrections to the fine structure, which contribute to the spin-dependent part of the Lamb shift. Our calculation focuses on the so-called ``two-loop self-energy'' involving two virtual closed photon loops. For bound states, this correction has proven to be notoriously difficult to evaluate. The calculation of the binding corrections to the bound-state two-loop self-energy is simplified by a separate treatment of hard and soft virtual photons. The two photon-energy scales are matched at the end of the calculation. We explain the significance of the mathematical methods employed in the calculation in a more general context, and present results for the fine-structure difference of the two-loop self-energy through the order of $\alpha^8$.Comment: 19 pages, LaTeX, 2 figures; J. Phys. A (in press); added analytic results for two-loop form-factor slopes (by P. Mastrolia and E. Remiddi