The emergence of macroscopic currents in photoconductive sampling of optical fields.

Photoconductive field sampling enables petahertz-domain optoelectronic applications that advance our understanding of light-matter interaction. Despite the growing importance of ultrafast photoconductive measurements, a rigorous model for connecting the microscopic electron dynamics to the macroscopic external signal is lacking. This has caused conflicting interpretations about the origin of macroscopic currents.

Breast-cancer detection using blood-based infrared molecular fingerprints.

Background: Breast cancer screening is currently predominantly based on mammography, tainted with the occurrence of both false positivity and false negativity, urging for innovative strategies, as effective detection of early-stage breast cancer bears the potential to reduce mortality. Here we report the results of a prospective pilot study on breast cancer detection using blood plasma analyzed by Fourier-transform infrared (FTIR) spectroscopy - a rapid, cost-effective technique with minimal sample volume requirements and potential to aid biomedical diagnostics. FTIR has the capacity to probe health phenotypes via the investigation of the full repertoire of molecular species within a sample at once, within a single measurement in a high-throughput manner.

Multi-octave, CEP-stable source for high-energy field synthesis.

The development of high-energy, high-power, multi-octave light transients is currently the subject of intense research driven by emerging applications in attosecond spectroscopy and coherent control. We report on a phase-stable, multi-octave source based on a Yb:YAG amplifier for light transient generation. We demonstrate the amplification of a two-octave spectrum to 25 μJ of energy in two broadband amplification channels and their temporal compression to 6 and 18 fs at 1 and 2 μm, respectively.

Near-PHz-bandwidth, phase-stable continua generated from a Yb:YAG thin-disk amplifier.

We report on the generation of a multi-octave, phase-stable continuum from the output of a Yb:YAG regenerative amplifier delivering 1-ps pulses with randomly varying carrier-envelope phase (CEP). The intrinsically CEP-stable spectral continuum spans from 450 nm to beyond 2500 nm, covering a spectral range of about 0.6 PHz.

Visualization of bond rearrangements in acetylene using near single-cycle laser pulses.

The migration of hydrogen atoms resulting in the isomerization of hydrocarbons is an important process which can occur on ultrafast timescales. Here, we visualize the light-induced hydrogen migration of acetylene to vinylidene in an ionic state using two synchronized 4 fs intense laser pulses. The first pulse induces hydrogen migration, and the second is used for monitoring transient structural changes via Coulomb explosion imaging.

Attosecond photoelectron streaking with enhanced energy resolution for small-bandgap materials.

Attosecond photoelectron streaking spectroscopy allows time-resolved electron dynamics with a temporal resolution approaching the atomic unit of time. Studies have been performed in numerous systems, including atoms, molecules, and surfaces, and the quest for ever higher temporal resolution called for ever wider spectral extent of the attosecond pulses. For typical experiments relying on attosecond pulses with a duration of 200 as, the time-bandwidth limitation for a Gaussian pulse implies a minimal spectral bandwidth larger than 9 eV translating to a corresponding spread of the detected photoelectron kinetic energies.

High-power, 1-ps, all-Yb:YAG thin-disk regenerative amplifier.

We report a 100 W, 20 mJ, 1-ps, all-Yb:YAG thin-disk regenerative amplifier seeded by a microjoule-level Yb:YAG thin-disk Kerr-lens mode-locked oscillator. The regenerative amplifier is implemented in a chirped pulse amplification system and operates at an ambient temperature in air, delivering ultrastable output pulses at a 5 kHz repetition rate and with a root mean square power noise value of less than 0.5%.

Real-time observation of valence electron motion.

The superposition of quantum states drives motion on the atomic and subatomic scales, with the energy spacing of the states dictating the speed of the motion. In the case of electrons residing in the outer (valence) shells of atoms and molecules which are separated by electronvolt energies, this means that valence electron motion occurs on a subfemtosecond to few-femtosecond timescale (1 fs = 10(-15) s). In the absence of complete measurements, the motion can be characterized in terms of a complex quantity, the density matrix.

Generation of sub-3 fs pulses in the deep ultraviolet.

We demonstrate generation and measurement of intense deep-ultraviolet light pulses with a duration of approximately 2.8 fs (FWHM of the intensity envelope) and a wavelength distribution between 230 and 290 nm. They emerge via direct frequency upconversion of sub-4 fs laser pulses of a carrier wavelength of approximately 750 nm focused into an Ne-filled, quasi-static gas cell.

Power scaling of a high-repetition-rate enhancement cavity.

A passive optical resonator is used to enhance the power of a pulsed 78 MHz repetition rate Yb laser providing 200 fs pulses. We find limitations relating to the achievable time-averaged and peak power, which we distinguish by varying the duration of the input pulses. An intracavity average power of 18 kW is generated with close to Fourier-limited pulses of 10 W average power.