Thomas Halfmann
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View article: Frequency up-conversion of midinfrared signals from resonantly enhanced nonlinear spectroscopy
Frequency up-conversion of midinfrared signals from resonantly enhanced nonlinear spectroscopy Open
We experimentally demonstrated and thoroughly investigated the up-conversion of midinfrared signals from nonlinear spectroscopy in a molecular gas to the regime of shorter wavelength to improve the features and applicability of such sensit…
View article: Light storage by electromagnetically induced transparency for one second at the level of a single photon in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mtext>Pr</mml:mtext> <mml:mrow> <mml:mn>3</mml:mn> <mml:mo>+</mml:mo> </mml:mrow> </mml:msup> <mml:mtext>:</mml:mtext> <mml:msub> <mml:mtext>Y</mml:mtext> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mtext>SiO</mml:mtext> <mml:mn>5</mml:mn> </mml:msub> </mml:mrow> </mml:math> prepared with multiple frequency ensembles
Light storage by electromagnetically induced transparency for one second at the level of a single photon in prepared with multiple frequency ensembles Open
Efficient and long-term storage of quantum information encoded in single photons is crucial for applications of optical quantum technologies, e.g. quantum repeaters in communication networks. Obviously, the maximal storage time is an impor…
View article: Editorial note for the J. Phys. B. special issue ‘Coherent Control: Photons, Atoms and Molecules’ honoring the life and work of Bruce W Shore
Editorial note for the J. Phys. B. special issue ‘Coherent Control: Photons, Atoms and Molecules’ honoring the life and work of Bruce W Shore Open
This special issue "Coherent Control: Photons, Atoms and Molecules", honors the life and work of Bruce W. Shore who passed away on January 9, 2021 at the age of 85.
View article: Detection of HCl molecules by resonantly enhanced sum-frequency mixing of mid- and near-infrared laser pulses
Detection of HCl molecules by resonantly enhanced sum-frequency mixing of mid- and near-infrared laser pulses Open
We perform experimental studies of resonantly enhanced sum-frequency mixing (SFM), driven by tunable, spectrally narrowband mid-infrared and fixed-frequency nanosecond laser pulses, aiming at applications in molecular gas detection. The mi…
View article: Ultrabright and narrowband intra-fiber biphoton source at ultralow pump power
Ultrabright and narrowband intra-fiber biphoton source at ultralow pump power Open
Nonclassical photon sources of high brightness are key components of quantum communication technologies. We here demonstrate the generation of narrowband, nonclassical photon pairs by employing spontaneous four-wave mixing in an optically-…
View article: Optical parametric oscillator and amplifier providing tunable, narrowband nanosecond laser pulses in the mid-infrared with mJ pulse energy
Optical parametric oscillator and amplifier providing tunable, narrowband nanosecond laser pulses in the mid-infrared with mJ pulse energy Open
We report on an all-solid-state light source for nanosecond (ns) laser pulses, with broad tunability in the mid-infrared, spectral bandwidth close to the Fourier transform limit, and pulse energy in the mJ regime. To this end, we extend a …
View article: Confining atomic populations in space via stimulated Raman adiabatic passage in a doped solid
Confining atomic populations in space via stimulated Raman adiabatic passage in a doped solid Open
We experimentally demonstrate spatial confinement of atomic excitation by adiabatic passage processes in a rare-earth ion-doped Pr 3+ :Y 2 SiO 5 crystal. In particular, we apply stimulated Raman adiabatic passage (STIRAP) and compare its p…
View article: Spatially strongly confined atomic excitation via a two dimensional stimulated Raman adiabatic passage
Spatially strongly confined atomic excitation via a two dimensional stimulated Raman adiabatic passage Open
We consider a method of sub-wavelength superlocalization and patterning of atomic matter waves via a two dimensional stimulated Raman adiabatic passage (2D STIRAP) process. An atom initially prepared in its ground level interacts with a do…
View article: Few-photon storage on a second timescale by electromagnetically induced transparency in a doped solid
Few-photon storage on a second timescale by electromagnetically induced transparency in a doped solid Open
We present the experimental demonstration of light storage towards the single photon level at a long storage time by electromagnetically induced transparency in a rare-earth ion-doped Pr 3+ :Y 2 SiO 5 crystal. We apply decoherence control …
View article: Loading and spatially resolved characterization of a cold atomic ensemble inside a hollow-core fiber
Loading and spatially resolved characterization of a cold atomic ensemble inside a hollow-core fiber Open
We present a thorough experimental investigation of the loading process of\nlaser-cooled atoms from a magneto-optical trap into an optical dipole trap\nlocated inside a hollow-core photonic bandgap fiber, followed by propagation of\nthe at…
View article: Universal composite pulses for efficient population inversion with an arbitrary excitation profile
Universal composite pulses for efficient population inversion with an arbitrary excitation profile Open
We introduce a method to rotate arbitrarily the excitation profile of universal broadband composite pulse sequences for robust high-fidelity population inversion. These pulses compensate deviations in any experimental parameter (e.g. pulse…
View article: Single-photon-level narrowband memory in a hollow-core photonic bandgap fiber
Single-photon-level narrowband memory in a hollow-core photonic bandgap fiber Open
An experimental platform operating at the level of individual quanta and providing strong light-matter coupling is a key requirement for quantum information processing. In our work, we show that hollow-core photonic bandgap fibers filled w…
View article: Third harmonic generation and microscopy, enhanced by a bias harmonic field
Third harmonic generation and microscopy, enhanced by a bias harmonic field Open
We present strong enhancements of the signal yield in third harmonic generation microscopy by seeding the optically nonlinear sample with some intensity at the third harmonic wavelength, in addition to the driving fundamental beam. By appl…
View article: Roadmap on STIRAP applications
Roadmap on STIRAP applications Open
STIRAP (stimulated Raman adiabatic passage) is a powerful laser-based method, usually involving two photons, for efficient and selective transfer of populations between quantum states. A particularly interesting feature is the fact that th…
View article: Stopped and stationary light at the single-photon level inside a hollow-core fiber
Stopped and stationary light at the single-photon level inside a hollow-core fiber Open
An experimental platform operating at the level of individual quanta and providing strong light-matter coupling is a key requirement for quantum information processing. We report on narrowband light storage and retrieval as well as station…
View article: Rephasing efficiency of sequences of phased pulses in spin-echo and light-storage experiments
Rephasing efficiency of sequences of phased pulses in spin-echo and light-storage experiments Open
We investigate the rephasing efficiency of sequences of phased pulses for\nspin echoes and light storage by electromagnetically induced transparency\n(EIT). We derive a simple theoretical model and show that the rephasing\nefficiency is ve…
View article: Experimental demonstration of composite stimulated Raman adiabatic passage
Experimental demonstration of composite stimulated Raman adiabatic passage Open
We experimentally demonstrate composite stimulated Raman adiabatic passage\n(CSTIRAP), which combines the concepts of composite pulse sequences and\nadiabatic passage. The technique is applied for population transfer in a\nrare-earth doped…
View article: Arbitrarily Accurate Pulse Sequences for Robust Dynamical Decoupling
Arbitrarily Accurate Pulse Sequences for Robust Dynamical Decoupling Open
We introduce universally robust sequences for dynamical decoupling, which simultaneously compensate pulse imperfections and the detrimental effect of a dephasing environment to an arbitrary order, work with any pulse shape, and improve per…
View article: Dispersion-enhanced third-harmonic microscopy
Dispersion-enhanced third-harmonic microscopy Open
We demonstrate strong enhancements of signal yield and image contrast in third-harmonic microscopy by appropriate choice of driving laser wavelength to modulate the phase-matching conditions of the conversion process by dispersion control.…
View article: Stationary light pulses and narrowband light storage in a laser-cooled ensemble loaded into a hollow-core fiber
Stationary light pulses and narrowband light storage in a laser-cooled ensemble loaded into a hollow-core fiber Open
We report on the first observation of stationary light pulses and narrowband\nlight storage inside a hollow-core photonic crystal fiber. Laser-cooled atoms\nwere first loaded into the fiber core providing strong light-matter coupling.\nLig…