Alexandria Anderson

Few-Femtosecond Plasmon Dephasing of a Single Metallic Nanostructure from Optical Response Function Reconstruction by Interferometric Frequency Resolved Optical Gating

The precise characterization of the ultrafast optical response of metals and metallic nanostructures has remained an experimental challenge. We probe the few-femtosecond electronic dephasing of a local surface plasmon polariton excitation using symmetry-selective second-harmonic (SH) Rayleigh scattering of a nanoscopic conical gold tip as an individual plasmonic nanostructure. The full reconstruction of the optical response function of the plasmon excitation with phase and amplitude without any model assumptions is demonstrated from the analysis of the two-dimensional spectrogram obtained by simultaneous time- and frequency-domain SH measurements, using interferometric frequency resolved optical gating. The measured dephasing time of T(2) = 18 +/- 5 fs indicates the plasmon damping is dominated by nonradiative decay, consistent with a Drude-Sommerfeld dielectric response for gold. Even for the nominally homogeneous localized plasmon response, deviations are observed from the ideal harmonic oscillator phase behavior, which may reflect the underlying inhomogeneous electronic response with its different scattering channels. The presented technique is generally applicable for the reconstruction of the plasmon dynamics of complex nanostructures: information that cannot be obtained by conventional dark-field scattering.

Close to transform-limited, few-cycle 12 µJ pulses at 400 kHz for applications in ultrafast spectroscopy

Non-collinear optical parametric amplification has become the leading technology for amplifying few-cycle carrier-envelope phase (CEP) stable pulses to high energy at extreme repetition rates. In this work, a parametric amplifier system devoted to ultrafast photoionization experiments with coincidence detection is reported. The amplifier delivers CEP-stable few-cycle pulses with an average power of 5 W, and operates at repetition rates between 400 and 800 kHz. Close to transform-limited compression of the few-cycle pulses is achieved with minimized spatio-temporal distortions. Potential limitations introduced by spatio-temporal couplings to applications in attosecond science are analyzed. In particular, it is shown that pulse front tilt resulting from non-collinear amplification can considerably reduce the asymmetry in stereo above threshold ionization (stereo-ATI) experiments.

Compact hollow fiber compression scheme for multi-mJ pulse generation

Circularly polarized, 25 fs 5 mJ pulses generated at a repetition rate of 1 kHz from a two-stage chirped pulse amplifier were spectrally broadened by means of nonlinear propagation in a Ne-filled hollow fiber. Subsequent compression with dispersive mirrors resulted in 5.2 fs, 1.7 mJ pulses. After recompression an all-reflective achromatic phase retarder was used to obtain linear polarization.

Improved Characteristics of High Repetition Rate Non-Collinear Optical Parametric Amplifiers for Electron-Ion Coincidence Spectroscopy

A non-collinear optical parametric amplifier (NOPA) for applications in attosecond science is presented. The amplifier delivers carrier-envelope phase (CEP) stable few-cycle pulses at an average power of 5 W at 400 and 800 kHz.

Strong field ionization of small hydrocarbon chains with full 3D momentum analysis

Strong field ionization of small hydrocarbon chains is studied in a kinematic complete experiment using a reaction microscope. By coincidence detection of ions and electrons different ionization continua populated during the ionization process are identified. In addition, photoelectron momentum distributions from laser-aligned molecules allow to characterize the electron wavepackets emerging from different Dyson orbitals.

Few-cycle pulses at 400 kHz for electron-ion coincidence experiments

A reaction microscope and an optical parametric amplifier delivering few-cycle pulses at 800 nm with pulse energies in the few-μJ range at 400 kHz are introduced. First results on strong field ionization are presented.

Long-term CEP-stable high energy few-cycle pulses using the feed-forward method

The feed-forward technique has recently revolutionized carrier-envelope phase stabilization, enabling unprecedented values of residual phase jitter. Nevertheless, in its original demonstrations the stabilized beam exhibited angular and temporal dispersion. We demonstrate that these problems can be solved, resulting in few-cycle pulses with good beam quality. This in turn enables the use of monolithic interferometers, providing excellent long-term stability of the system. Out-of-loop RMS phase noise of less than 80 mrad over 33 minutes (0.5 mHz to 5 kHz) is measured, i.e., a value that has previously been reported for a few seconds integration time. The current method promises to enable reliable operation of CEP-stable systems over several days.

Sub-poissonian noise signatures in the carrier-envelope phase jitter of highly stabilized mode-locked lasers

Measurement and stabilization of the carrier-envelope phase (CEP) drift of femtosecond pulse trains has found widespread application in frequency metrology and high-field nonlinear optics [1]. Stabilization of the CEP is typically accomplished in a feedback loop, acting on the pump power with a wide-bandwidth modulator. This stabilization strongly relies on the fact that a change of intracavity laser power results in a proportional change of the carrier envelope frequency ƒCE. This proportionality may be turned around, with ƒCE acting as a probe for the laser intracavity power. Doing so, we find that this novel method of intracavity power measurements is not limited by standard shot noise, with a sensitivity of the method down to −17 dB (i.e., a factor 50) below the shot noise floor of conventional photodetection in a photodiode or similar absorptive devices. This opens a perspective for highly sensitive interferometry applications.

Tabletop generation of carrier envelope phase stabilized multi-mJ few-cycle pulses

A compact system for the generation of few-cycle multi-mJ carrier envelope phase (CEP) stabilized pulses is presented. The output 5.4 fs, 1.9 mJ pulses have CEP noise of only 190 mrad rms over seven hours.

Time-domain optical response function reconstruction of an individual plasmonic nanostructure

The precise characterization of the ultrafast electronic response in a metallic nanostructure is achieved using a combination of spectrogram measurement of collinear interferometric second-harmonic scattering and treatment of Frequency Resolved Optical Gating (FROG). The plasmon dephasing dynamics have been resolved with multiple time-scales.