A. Leitenstorfer

Amplitude and Phase Resolved Detection of Tunable Femtosecond Pulses with Frequency Components beyond 100 THz

The electric field amplitude and phase of ultrashort transients generated by phase-matched optical rectification in GaSe is detected via ultrabroadband electro-optic sampling. Full tunability is achieved between 6 μm and 40 μm with pulse durations below 50 fs. Frequency components approaching the near infrared regime are observed.

Femtosecond buildup of Coulomb screening in photoexcited GaAs probed via ultrabroadband THz spectroscopy

Abstract On a femtosecond time scale, we observe how Coulomb screening builds up in a nonequilibrium electron–hole plasma photogenerated in GaAs within 10xa0fs. To this end, the dynamics of the complex dielectric function throughout the mid infrared is directly probed with uncertainty-limited temporal resolution by means of ultrabroadband THz spectroscopy. While the system becomes conducting instantaneously, the onset of collective behavior such as Coulomb screening and plasmon scattering exhibits a delayed rise. The time scale for these phenomena is of the order of the inverse plasma frequency. Our findings support recent quantum kinetic simulations.

Ultrafast Conductivity and Lattice Dynamics of Insulator-Metal Phase Transition in VO2 Studied via Multi-Terahertz Spectroscopy

The mid-infrared ultrafast response of VO2 thin films following 10 fs interband excitation is investigated as a function of sample temperature and laser fluence. The dynamics of the terahertz conductivity provides an insight into the microscopic details of the phase transition.

Full-band Monte Carlo simulations of photo excitation in silicon diode structures

In this study, a full-band particle-based simulator is used to model photo-generated electron–hole pairs in Si to investigate ultra-fast charge transport. This work is motivated by previous simulations of transient transport in III–V material as well as recent experimental measurements of optically excited Si pin diodes. The simulation results show evidence of velocity overshoot at high fields (greater than 100 kV cm−1), and can be attributed to momentum relaxation.

THz carrier oscillations in GaAs heterostructures detected via two color femtosecond pump probe spectroscopy

Realistic Monte Carlo simulations as well as first experimental data show that classical, quasi ballistic, phase-coherent electron oscillations are possible in relative wide suitably designed confining potentials. Three different confining potentials have been investigated and the oscillation frequencies expected from the calculations were observed in the pump & probe experiments.

Fullband Particle-Based Simulation of High-Field Transient Transport in III–V Semiconductors

Motivated by recent experimental measurements (A. Leitenstorfer et al., 2000. Physical Review B 61(24): 16642–16652), this work presents the transient analysis of photogenerated electron-hole pairs in GaAs and InP pin diodes (S. M. Sze, 1981. Physics of Semiconductor Devices, 2nd edn., John Wiley) using a fullband particle-based simulator (M. Saraniti and S. Goodnick, 2000. IEEE Transactions on Electron Devices 47(10): 1909–1915). The fullband simulation tool is based on a particle-based technique that has been developed to reduce the computational time required for modeling charge transport phenomena in semiconductors. Excellent agreement is found between experiment and simulation of transient acceleration and velocity overshoot in GaAs and InP pin diodes due the femto-second optical excitation of carriers.

Coherent Excitonic and Free Carrier Dynamics in Bulk GaAs and Heterostructures

Coherent dynamics in atomic and molcular systems has been investigated for a long time. The first spin echo experiment1 was performed in 1950 on protons in a water solution of Fe+++ ions. Pulses in the radio frequency range were generated by means of a gated oscillator with pulse widths between 20 μs and a few milliseconds. With these pulses dephasing times of the order of 10 ms have been measured. In the 1960s echo experiments were brought into the visible range.2,3 A Q-switched ruby laser produced pulses of approximately 10 ns duration which were used to observe photon echoes from ruby. In this case the dephasing times were of the order of 100 ns. For the observation of such coherent dynamics the pulse width has to be shorter than the dephasing time. In semiconductors typical dephasing times are much shorter, they are in the range of a few picoseconds down to some femtoseconds. Therefore, experiments had to wait until the development of suitable lasers which were able to generate sub-picosecond pulses.

Single-cycle light pulses from a compact Er:fiber laser

We demonstrate a setup based entirely on compact Er:fiber technology which synthesizes pulses of a duration of 4.3 fs. This value corresponds to a single cycle of light in the telecom wavelength region.

How fast electrons and photons mix: Sub-cycle switching of intersubband cavity polaritons

Intersubband cavity polaritons in a quantum well waveguide structure are optically generated within less than one cycle of light by a femtosecond near-infrared pulse. Mid-infrared probe transients trace the non-adiabatic switch-on of ultrastrong light-matter coupling and the conversion of bare photons into cavity polaritons directly in the time domain.

Two-branch Er:fiber laser emitting 11 fs tunable pulses with attosecond relative timing jitter

We present an Er:fiber laser generating two 11 fs pulse trains individually tunable between 1200 and 1300 nm. A relative timing jitter of 43 as is measured after frequency conversion and compression.