A5026527794- Advanced Frequency and Time Standards
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Fiber Laser Technologies
- Atomic and Subatomic Physics Research
- Spectroscopy and Laser Applications
- Photorefractive and Nonlinear Optics
- Atomic and Molecular Physics
- Solid State Laser Technologies
- Photonic and Optical Devices
- Mechanical and Optical Resonators
- Geophysics and Sensor Technology
- Quantum optics and atomic interactions
- Quantum Mechanics and Applications
- Quantum Information and Cryptography
- Noncommutative and Quantum Gravity Theories
- Laser Design and Applications
- Mass Spectrometry Techniques and Applications
- Pulsars and Gravitational Waves Research
- Dark Matter and Cosmic Phenomena
- Laser-Matter Interactions and Applications
- Relativity and Gravitational Theory
- Cosmology and Gravitation Theories
- Semiconductor Lasers and Optical Devices
- Atmospheric Ozone and Climate
- Geophysics and Gravity Measurements
Heinrich Heine University Düsseldorf
2016-2025
University of Kassel
2022
Institute for Experimental Psychophysiology (Germany)
2010-2021
University of Konstanz
1993-2005
Humboldt-Universität zu Berlin
2003
University of Koblenz and Landau
1996-2002
Stanford University
1990-1993
University of Florida
1988
Kansas State University
1975
We have reconstructed the quantum state of optical pulses containing single photons using method phase-randomized pulsed homodyne tomography. The single-photon Fock 1> was prepared conditional measurements on photon pairs born in process parametric down-conversion. A probability distribution phase-averaged electric field amplitudes with a strongly non-Gaussian shape is obtained total detection efficiency (55+/-1)%. angle-averaged Wigner function from this shows strong dip reaching...
A method is proposed for performing accurate spectral characterization of samples with frequency combs, e.g., from mode-locked lasers, over the range covered by combs. The essence use two combs slightly different mode spacing to achieve resolution. advantages are speed, resolution, sensitivity, absence dispersive components, and high spatial
We report on a new test of Lorentz invariance performed by comparing the resonance frequencies two orthogonal cryogenic optical resonators subject to Earth's rotation over $\ensuremath{\sim}1\text{ }\mathrm{y}\mathrm{r}$. For possible anisotropy speed light $c$, we obtain ${\ensuremath{\Delta}}_{\ensuremath{\theta}}c/{c}_{0}=(2.6\ifmmode\pm\else\textpm\fi{}1.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$. Within Robertson-Mansouri-Sexl (RMS) theory, this implies an isotropy...
We report the reconstruction of quantum state squeezed vacuum generated by a continuous-wave optical parametric amplifier. Homodyne detection and tomographic methods were used to obtain density matrix in Fock (number state) representation. The photon number distribution exhibits odd-even oscillations, manifestation pair production second-order nonlinear medium.
By measurement of the frequency a vibrational overtone transition in molecular hydrogen ion ${\mathrm{HD}}^{+}$, we demonstrate first optical spectroscopy trapped ions with submegahertz accuracy. We use diode laser, locked to stable comb, perform resonance-enhanced multiphoton dissociation on sympathetically cooled ${\mathrm{HD}}^{+}$ at 50 mK. The achieved 2-ppb relative accuracy is factor 150 higher than previous results for and measured agrees well recent high-accuracy ab initio...
The mode spectrum of a 3.8-cm-diameter fused-silica sphere has been studied in the vicinity 1.06 microm. A single-frequency Nd:YAG laser was used to excite whispering gallery modes by means evanescent wave coupling. is excellent agreement with predictions from Mie theory.
We report on the results of a strongly improved test local Lorentz invariance, consisting search for an anisotropy resonance frequencies electromagnetic cavities. The apparatus comprises two orthogonal standing-wave optical cavities interrogated by laser, which were rotated approximately 175 000 times over duration 13 months. measurements are interpreted as speed light, within Robertson-Mansouri-Sexl (RMS) and standard model extension (SME) photon sector theories. find no evidence isotropy...
We propose to use laser spectroscopy of ultracold molecules establish improved limits on the time independence electron-to-nuclear and nuclear-nuclear mass ratios by comparing, via an optical frequency comb, frequencies suitable sets transitions in ground electronic state. Hydrogen molecular ions trapped a radiofrequency trap, sympathetically cooled atomic ions, are identified as accessible system. show that dipole-allowed rovibrational transition $\mathrm{H}{\mathrm{D}}^{+}$ probes for...
The precise measurement of transition frequencies in cold, trapped molecules has applications fundamental physics, and extremely high accuracies are desirable. We determine suitable candidates by considering the simplest with a single electron, for which external-field shift corrections can be calculated theoretically precision. Our calculations show that H2+ exhibits particular transitions whose fractional systematic uncertainties may reduced to 5×10−17 at room temperature. also generalize...
Advanced techniques for manipulation of internal states, standard in atomic physics, are demonstrated a charged molecular species the first time. We address individual hyperfine states rovibrational levels diatomic ion by optical excitation transitions, and achieve controlled transfer population into selected state. use hydrogen ions (${\mathrm{HD}}^{+}$) as model system employ novel frequency-comb-based, continuous-wave $5\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ laser spectrometer. The...
Optical lattice clocks with uncertainty and instability in the $10^{-17}$-range below have so far been demonstrated exclusively using fermions. Here, we demonstrate a bosonic optical clock $3\times 10^{-18}$ $2.0\times 10^{-17}$ accuracy, both values improving on previous work by factor 30. This was enabled probing transition an ultra-long interrogation time of 4 s, long coherence provided cryogenic silicon resonator, careful stabilization relevant operating parameters, at low atom density....
An optomechanical sensor suitable for the study of quantum effects has been developed and characterized. The reads out vibrations a microfabricated miniature silicon mechanical oscillator which forms one end mirror high finesse Fabry-P\'erot cavity. quality factor is up to $Q=300000$ at 300 K rises $Q=4\ifmmode\times\else\texttimes\fi{}{10}^{6}$ 4 K. thermal noise measured in time frequency domains room temperature 4.5 prospects observing standard limit are discussed.
Diode-laser-pumped Nd:YAG lasers were frequency stabilized by locking their frequency-doubled output to Doppler-free absorption lines of the 127I2 molecule. The successive two-sample deviation beat between two independent iodine-stabilized is less than 650 Hz, or 2.3 × 10−12 laser frequency, for averaging times 24 and 80 s.
A test of Lorentz invariance for electromagnetic waves was performed by comparing the resonance frequencies two optical resonators as a function orientation in space. In terms Robertson-Mansouri-Sexl theory, we obtain $\ensuremath{\beta}\ensuremath{-}\ensuremath{\delta}\ensuremath{-}1∕2=(+0.5\ifmmode\pm\else\textpm\fi{}3\ifmmode\pm\else\textpm\fi{}0.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$, tenfold improvement compared to previous best results. We also set first upper...
A high-order asymptotic expansion for the size parameters x(n)((l)) of electromagnetic resonances large spherical dielectric scatterers is reported. The calculated up to order n(-8/3), where n mode number and valid small orders l. Its accuracy studied as a function n, l, refractive index. For l = 1 mode, relative better than 10(-4) > 50.
We have cooled ensembles of the molecular hydrogen ions $\mathrm{H}_{2}{}^{+}$, $\mathrm{H}_{3}{}^{+}$, and all their deuterated variants to temperatures a few mK in radio frequency trap, by sympathetic cooling with laser-cooled beryllium ions. The are embedded central regions Coulomb crystals. Mass spectroscopy dynamics simulations were used accurately characterize properties ultracold multispecies demonstrate species-selective purification ensembles. These molecules fundamental importance...
Gas-phase singly protonated organic molecules of mass 410 Da (Alexa Fluor 350) have been cooled from ambient temperature to the hundred millikelvin range by Coulomb interaction with laser-cooled barium ions. The were generated an electrospray ionization source, transferred and stored in a radio-frequency trap together atomic Observations are well described molecular dynamics simulations, which used determine spatial distribution thermal energy molecules. In one example, ensemble 830 138Ba+...
We study the prospects of using transitions from ytterbium ground state to metastable states $^3{\rm P}^{\rm o}_2$ at $E=19\,710.388~$cm$^{-1}$ and $4f^{13}5d6s^2\,(J=2)$ $E=23\,188.518~$cm$^{-1}$ as clock in an optical lattice clock. Having more than one transition Yb could benefit search for new physics beyond Standard Model via studying non-linearity King's plot or time-variation ratio frequencies two transitions. calculate lifetime states, relevant amplitudes, systematic shifts,...