M. V. Tognetti

Sub-two-cycle pulses by soliton self-compression in highly nonlinear photonic crystal fibers

We demonstrate the direct generation of sub-two-cycle pulses by soliton self-compression of femtosecond pulses from a Ti:sapphire laser at 85 MHz using a 4.85-mm-long highly nonlinear photonic crystal fiber. Sub-nanojoule, 41 fs input pulses were compressed down to 4.6 fs without additional phase compensation schemes. To our knowledge, these are the shortest pulses obtained by soliton-effect compression of a laser oscillator. Efficient, near-dispersionless collimation of the fiber output was achieved with a simple lens and an octave-spanning double-chirped mirror pair. The full electric field of the compressed pulses was retrieved with a genetic algorithm applied to spectral and interferometric autocorrelation measurements, and the results are well described by numerical simulations.

Maximal coherence in a three-level autoionizing atom for the generation of subpicosecond pulses in the extreme ultraviolet

We discuss the possibility of using a three-level ladder atomic system, with a final autoionizing state, for the efficient generation of short radiation pulses in the extreme ultraviolet through a process of sum-frequency mixing in the presence of maximal coherence. The results of numerical calculations are presented, investigating the effects of photoionization, dynamic Stark shift and electron impact dephasing on the conversion efficiency in a single atom model. The results of this investigation can be useful in identifying a real candidate for a possible experiment.

A Titanium-doped-sapphire laser source with tunable frequency, single-mode emission, and adjustable pulse duration

We present a laser source with several desirable characteristics, such as tunable wavelength in the near infrared, single-longitudinal-mode emission and variable pulse temporal duration in the nanosecond regime. The laser is based on an injection-seeded Titanium-doped-sapphire ring cavity. Our experiments show how the pulse duration can be varied in a controllable fashion either by changing the cavity length or by changing the pump energy. We present a theoretical model which successfully reproduces the experimental results by treating the operation of this type of laser as a gain-switching technique. As far as the stabilization of the laser cavity, we also present a novel solution involving the use of an avalanche photodiode.

Temporal compression of short-wavelength laser pulses by coherent control in rare gases

We present a theoretical study of temporal compression of a short-wavelength laser pulse predicted in a real, Doppler-broadened, atomic system. The compression is the result of the coherent control peculiarities of electromagnetically induced transparency-propagation dynamics. Numerical results are reported and discussed, showing a temporal compression of 2 orders of magnitude (from 10 ns to 100 ps) of a 106.7-nm laser pulse in argon atoms at room temperature.

Controllable optical delay of wideband laser pulses by means of coherent effects

We report the first experimental observation of controllable temporal delay of wideband laser pulses (input spectral bandwidth of 3.3 GHz) using electromagnetically induced transparency. We obtain this result with limited temporal distortion of our pulses and excellent values of the delay-bandwidth product. Our experimental results are in agreement with a theoretical analysis.

Laser-pulse compression by coherent control in a Doppler-broadened medium: Analytical and numerical studies

We have studied the temporal compression of laser pulses occurring in a scheme based on the coherent control peculiarities of electromagnetically induced transparency. This work extends earlier model studies, including the effect of Doppler broadening in a real hot medium. For definiteness and consistency of the atomic parameters employed, we have treated a scheme in argon. In this way, we establish a realistic model that enables us to predict quantitatively the performance of laser pulse compression experiments.

Temporal Compression of Laser Pulses by Coherent Control

We present our most recent theoretical results on a temporal compression technique based on electromagnetically‐induced transparency. An experiment aimed to provide a first proof‐of‐principle demonstration of the process is also described.