A. ten Wolde

High-power femtosecond dye laser with tunable wavelength, pulse duration and chirp

Abstract We present a high-power femtosecond dye-laser system based on a CPM oscillator. The pulses have an energy up to 0.6 mJ and a variable pulse duration between 70 fs and 5 ps. The wavelength of the pulses is tunable throughout the visible, and the chirp of the pulses can be varied continuously.

Intensity-induced chirped Rydberg wavepackets: a new way of creating short light pulses

The authors report calculations on the time evolution of a Rydberg wavepacket excited with a short intense laser pulse. The wavepacket is chirped and compressed due to the AC Stark shift of the Rydberg states. This effect can be used to shorten optical pulses ranging from the IR to the UV regime. For a practical case, reduction of the duration of femtosecond pulses by a factor of six is predicted.

Measurement of picosecond‐pulse durations in the ultraviolet

A cross correlator for measurements of ultrashort UV pulses is described. The optical system is based on down‐conversion of the UV pulses. The system can also be used to measure the second‐ and third‐order autocorrelation function of pulses in the visible. The system is experimentally tested with UV pulses of 23‐ps duration, that appear to be symmetric.

Return of an electronic wavefunction to the core

Picosecond laser pulses are used to excite xenon atoms to Rydberg states and photoionise in a three-plus-one-photon ionisation process. When high Rydberg levels are excited, an electronic wavepacket is created. This wavepacket does not return to the core during the laser pulse: the direct four-photon ionisation is not enhanced. When lower Rydberg levels are excited the electronic wavefunction does return to the core: the ionisation is enhanced. The authors observe the transition from enhanced to non-enhanced ionisation.

Similarities between atomic wave packets and optical pulses

Abstract We consider the similarities between short optical pulses and atomic electron wave packets. The atomic potential acts in a similar way on the electron wave function as an optical cavity does on electromagnetic waves. It is shown that effects well known in optics, such as creation of pulsed light, dispersion, and shortening of optical pulses, can also occur for matter waves.

Time domain effects in photoionisation of Rydberg atoms

The authors report wavelength spectra of the photoelectron yield resulting from three-photon ionisation and four-photon excess-photon ionisation (EPI/ATI) of xenon in a magnetic field. The spectra are scanned over a wavelength region of 1 nm to 307 nm (three-photon threshold for ionisation of Xe). The EPI behaviour is studied while they scan through the threshold. They conclude from the measurements that the phenomena which are typical for EPI do not only take place above the threshold, but also below it as long as the ionisation pulse is short compared with the time period that elapses before the wavefunction of the intermediate state is relocalised around the core. This time period is at least one classical revolution, but is increased in this experiment by the application of a magnetic field.

Experiments on Rydberg Wave Packets

Under the influence of the development of lasers producing tunable ultra-short pulses, there has been an increased interest in the behavior of electronic wave packets during the last few years. An extensive overview of the field, with an emphasis on the theory, has been given in two theoretical papers1’2. The central theme of the present paper is the experimental observation of atomic electron wave packets.

Atomic Wave Packets and Optical Pulses

In this contribution we will consider the similarities between atomic electron wave packets and short optical pulses. It will be shown that well known effects in optics, such as dispersion, modulation of the group velocity, and shortening of pulses, can also occur for matter waves.

Observation of electronic wave packets with short laser pulses

A coherent superposition of Rydberg states leads to a radially localized wave packet. This wave packet oscillates between the turning points of the classical Kepler orbit. The energy spacings between the Rydberg states determines the oscillation time. The differences in the spacings cause the effects of dispersion and revival of the wave packet. Photoionization is a sensitive probe to the amount of wave function near the core, because in a Coulomb potential ionization takes place only near the atomic core. In the experiment, a wave packet is created by coherent excitation of Rydberg states of Rb with a short laser pulse, and detected by photoionization with a delayed probe pulse. In this way two returns of the wave packet are observed.