Steven L. Johnson
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View article: Generation of Intense Ultrashort Deep-Ultraviolet Pulses at 200 nm
Generation of Intense Ultrashort Deep-Ultraviolet Pulses at 200 nm Open
View article: Tuning chirality amplitude at ultrafast timescales in chiral <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>CsCuCl</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>
Tuning chirality amplitude at ultrafast timescales in chiral Open
Chirality is a fundamental symmetry concept relevant to many scientific fields. It describes discrete states, i.e., left-handed, right-handed, or achiral. In contrast to this discrete classification, objects can be continuously distorted. …
View article: Ultra-narrowband Coherent THz Source by Chirped-Pulse Difference Frequency Generation
Ultra-narrowband Coherent THz Source by Chirped-Pulse Difference Frequency Generation Open
We report the generation of extremely narrowband, micro-Joule-level, frequency-tunable THz pulses between 3 and 4 THz in organic DSTMS, without applying any spectral filtering techniques (e.g., bandpass filters). Using difference frequency…
View article: Mid-infrared element-specific selective manipulation of the ultrafast magneto-optical Kerr effect dynamics in the ferrimagnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>FeCr</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mi mathvariant="normal">S</mml:mi> <mml:mn>4</mml:mn> </mml:msub> </mml:mrow> </mml:math>
Mid-infrared element-specific selective manipulation of the ultrafast magneto-optical Kerr effect dynamics in the ferrimagnet Open
FeCr 2 S 4 is a ferrimagnet with two oppositely ordered spin sublattices (Fe and Cr), connected via superexchange interaction, giving a nonzero net magnetic moment. We show, using time-resolved measurements of the magneto-optic Ker…
View article: Perspective: an X-ray view of the coherent driving of materials
Perspective: an X-ray view of the coherent driving of materials Open
We discuss new opportunities in the study of materials arising from combining high intensity, phase-stable light pulses in the THz and mid-infrared with current and upcoming instrumentation at X-ray free electron laser (XFEL) facilities. W…
View article: Author Correction: Observation of polarization density waves in SrTiO3
Author Correction: Observation of polarization density waves in SrTiO3 Open
View article: Observation of polarization density waves in SrTiO3
Observation of polarization density waves in SrTiO3 Open
View article: High-power femtosecond mid-IR source with tunable center frequency and chirp
High-power femtosecond mid-IR source with tunable center frequency and chirp Open
We present an experimental implementation of a chirped mid-infrared (mid-IR) high-power laser source with variable center frequency between 4 and 30 THz and continuously tunable frequency sweep of up to 20% within one pulse, with a pulse d…
View article: Roles of band gap and Kane electronic dispersion in the terahertz-frequency nonlinear optical response in HgCdTe
Roles of band gap and Kane electronic dispersion in the terahertz-frequency nonlinear optical response in HgCdTe Open
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View article: Coherent control of rare earth 4f shell wavefunctions in the quantum spin liquid Tb2Ti2O7
Coherent control of rare earth 4f shell wavefunctions in the quantum spin liquid Tb2Ti2O7 Open
The resonant excitation of electronic transitions with coherent laser sources creates quantum coherent superpositions of the involved electronic states. Most time-resolved studies have focused on gases or isolated subsystems embedded in in…
View article: Erratum: Photoinduced structural dynamics of multiferroic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>TbMnO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math> [Phys. Rev. B <b>106</b>, 214312 (2022)]
Erratum: Photoinduced structural dynamics of multiferroic [Phys. Rev. B <b>106</b>, 214312 (2022)] Open
Received 16 February 2024DOI:https://doi.org/10.1103/PhysRevB.109.139902©2024 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAntiferromagnetismElectron-phonon couplingFerroelectricityLaser-induced demagnetizationLat…
View article: Roles of band gap and Kane electronic dispersion in the THz-frequency nonlinear optical response in HgCdTe
Roles of band gap and Kane electronic dispersion in the THz-frequency nonlinear optical response in HgCdTe Open
Materials with linear electronic dispersion often feature high carrier mobilities and unusually strong nonlinear optical interactions. In this work, we investigate the THz nonlinear dynamics of one such material, HgCdTe, with an electronic…
View article: Observation of polarization density waves in SrTiO3
Observation of polarization density waves in SrTiO3 Open
The nature of the "failed" ferroelectric transition in SrTiO3 has been a long-standing puzzle in condensed matter physics. A compelling explanation is the competition between ferroelectricity and an instability with a mesoscopic modulation…
View article: Generation of millijoule-level sub-5 fs violet laser pulses
Generation of millijoule-level sub-5 fs violet laser pulses Open
We demonstrate the generation, spectral broadening and post-compression of second harmonic pulses using a thin beta barium borate (BBO) crystal on a fused-silica substrate as the nonlinear interaction medium. By combining second harmonic g…
View article: Ultrafast all-optical manipulation of the charge-density wave in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>VTe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>
Ultrafast all-optical manipulation of the charge-density wave in Open
The charge-density-wave (CDW) phase in the layered transition-metal dichalcogenide VTe_{2} is strongly coupled to the band inversion involving vanadium and tellurium orbitals. In particular, this coupling leads to a selective disappearance…
View article: Non-equilibrium dynamics of spin-lattice coupling
Non-equilibrium dynamics of spin-lattice coupling Open
Quantifying the dynamics of normal modes and how they interact with other excitations is of central importance in condensed matter. Spin-lattice coupling is relevant to several sub-fields of condensed matter physics; examples include spint…
View article: Coherent control of orbital wavefunctions in the quantum spin liquid $Tb_{2}Ti_{2}O_{7}$
Coherent control of orbital wavefunctions in the quantum spin liquid $Tb_{2}Ti_{2}O_{7}$ Open
Resonant driving of electronic transitions with coherent laser sources creates quantum coherent superpositions of the involved electronic states. Most time-resolved studies have focused on gases or isolated subsystems embedded in insulatin…
View article: Generation of 210 GW few-cycle ultraviolet laser pulses
Generation of 210 GW few-cycle ultraviolet laser pulses Open
We demonstrate generation, spectral broadening, and post-compression of ultraviolet pulses using a thin BBO crystal on a fused silica substrate as the nonlinear interaction medium. By combining the second harmonic generation in the BBO cry…
View article: Self-compression of femtosecond laser pulses in ambient air
Self-compression of femtosecond laser pulses in ambient air Open
We demonstrate the self-compression of 98 fs near-infrared laser pulses down to 8.8 fs in ambient air, utilizing self-phase modulation in air and negative dispersion in the properties of a laser-induced plasma. The blue-shifted pulses achi…
View article: Self-compression of femtosecond laser pulses in ambient air
Self-compression of femtosecond laser pulses in ambient air Open
We demonstrate the self-compression of 98 fs near-infrared laser pulses down to 8.8 fs in ambient air, utilizing self-phase modulation in air and negative dispersion in the properties of a laser-induced plasma. The blue-shifted pulses achi…
View article: Non-equilibrium dynamics of spin-lattice coupling
Non-equilibrium dynamics of spin-lattice coupling Open
Collective excitations that involve both vibrational and magnetic characters, arising from strong coupling between the lattice and spins, are of fundamental interest in ultrafast manipulation of magnetization. Although previous experimenta…
View article: Ultrafast all-optical manipulation of the charge-density-wave in VTe$_{2}$
Ultrafast all-optical manipulation of the charge-density-wave in VTe$_{2}$ Open
The charge-density wave (CDW) phase in the layered transition-metal dichalcogenide VTe$_{2}$ is strongly coupled to the band inversion involving vanadium and tellurium orbitals. In particular, this coupling leads to a selective disappearan…
View article: Magnetoelectrics and multiferroics: theory, synthesis, characterisation, preliminary results and perspectives for all-optical manipulations
Magnetoelectrics and multiferroics: theory, synthesis, characterisation, preliminary results and perspectives for all-optical manipulations Open
Solid state compounds exhibiting multiple and coupled macroscopic orders, named multiferroics, represent a challenge for both theoretical and experimental modern condensed-matter physics. Spins and the electric polarisation in conventional…
View article: Non-equilibrium dynamics of spin-lattice coupling
Non-equilibrium dynamics of spin-lattice coupling Open
Interactions between the different degrees of freedom form the basis of many manifestations of intriguing physics in condensed matter. In this respect, quantifying the dynamics of normal modes that themselves arise from these interactions …
View article: Solid-state biased coherent detection of ultra-broadband terahertz pulses generated in a spintronic emitter for high repetition rate, low pulse energy lasers
Solid-state biased coherent detection of ultra-broadband terahertz pulses generated in a spintronic emitter for high repetition rate, low pulse energy lasers Open
We report the coherent generation and detection of terahertz (THz) pulses featuring a spectral bandwidth in the range of 0.1-9 THz achieved via the use of a high repetition rate (250 kHz), low pulse energy (6.2 µJ) laser system. More speci…
View article: Strong modulation of carrier effective mass in WTe2 via coherent lattice manipulation
Strong modulation of carrier effective mass in WTe2 via coherent lattice manipulation Open
View article: Impact ionization in low-band-gap semiconductors driven by ultrafast THz excitation: beyond the ballistic regime
Impact ionization in low-band-gap semiconductors driven by ultrafast THz excitation: beyond the ballistic regime Open
Using two-dimensional THz spectroscopy in combination with numerical models, we investigate the dynamics linked to carrier multiplication caused by high-field THz excitation of the low-gap semiconductor InSb. In addition to previously obse…
View article: Terahertz displacive excitation of a coherent Raman-active phonon in V2O3
Terahertz displacive excitation of a coherent Raman-active phonon in V2O3 Open
View article: Terahertz displacive excitation of a coherent Raman-active phonon in V2O3
Terahertz displacive excitation of a coherent Raman-active phonon in V2O3 Open
Nonlinear processes involving frequency-mixing of light fields set the basis for ultrafast coherent spectroscopy of collective modes in solids. In certain semimetals and semiconductors, generation of coherent phonon modes can occur by a di…
View article: Melting of magnetic order in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>NaOsO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math> by femtosecond laser pulses
Melting of magnetic order in by femtosecond laser pulses Open
NaOsO3 has recently attracted significant attention for the strong coupling between its electronic band structure and magnetic ordering. Here, we used time-resolved magnetic x-ray diffraction to determine the timescale of the ph…