D. Faccio

Enhanced detection of broadband terahertz fields via the filamentation of chirped optical pulses

We show that by employing positively chirped optical probe pulses above a critical power it is possible to enhance the detection bandwidth and signal obtained by Air Biased Coherent Detection scheme for broadband terahertz fields.

Electric-field induced second-harmonic FROG characterization of long-wavelength, few-cycle pulses

We describe a method for electric-field characterization of few-cycles pulses with wavelengths from mid-infrared to the THz region, based on electric-field induced second harmonic spectrograms. The method is demonstrated with single cycle THz pulses.

Comment on "Hawking Radiation from Ultrashort Laser Pulse Filaments" Reply

A comment by R. Schutzhold et al. raises possible concerns and questions regarding recent measurements of analogue Hawking radiation. We briefly reply to the opinions expressed in the comment and sustain that the origin of the radiation may be understood in terms of Hawking emission.

Generation and control of coherent conical pulses in seeded optical parametric amplification

We propose a new technique for high-energy conical pulse generation based on continuum seeded parametric amplification process in quadratic nonlinear media. We show that by using an appropriate broadband week seed we are able to lock the many spatiotemporal modes of the parametric radiation to obtain a single, coherent conical pulse.

Controlled X wave formation in bulk quadratic and cubic nonlinear media

Here we report spontaneous conical wave formation in quadratic and cubic nonlinear media, demonstrating how the characteristics of the formed conical wave strictly depend on those of the pumping source.

Demonstration of spontaneously generated conical waves during ultrashort laser pulse filamentation in air

Measurements and simulations show that X-waves are spontaneously generated during filamentation in air. This explains the sub-diffractive propagation of filaments beyond the end of the plasma channel generated by multiphoton ionization.

Pulse compression and X wave generation by Cross-Phase-Modulation induced spatiotemporal reshaping

Filamentation dynamics in the normal group-velocity-dispersion regime (in condensed media) is interpretable in terms of the spontaneous formation of X waves that is, stationary (non-dispersive and non-diffractive) wave packets characterized by a central high-intensity spike surrounded by slowly decaying tails that continuously sustain the central peak through a refuelling mechanism. Here we investigate numerically and experimentally the role of Cross-Phase-Modulation (XPM) from an intense pump to a weaker seed signal in the presence of pump filamentation.

Spontaneous X-pulse generation in a Kerr medium

This study utilizes a new nonlinear 3D-mapping technique and gives the first direct experimental demonstration of spontaneous X-pulse generation in a Kerr medium with NGVD. This work also shows how an ultrashort laser pulse collapses and then relaxes to a state characterized by a definite X-shaped spatiotemporal profile. This claim is supported by numerical simulations that show a good agreement with experimental data and outline the main dynamical features of X-wave formation.

Nonlinear unbalanced conical waves: localization and stationary propagation in nonlinear media with dissipation

This study presents an alternative type of multidimensional localization and stationarity in nonlinear media, based on conical waves, which is robust against nonlinear dissipation. This work also investigates the stability properties of nonlinear conical waves. The results indicate that nonlinear absorption acts as a stabilizing mechanism against small perturbations, since nonlinear conical waves become stable for nonlinear absorption strength above a certain threshold. The unique property of stationarity along with energy transfer to matter could make nonlinear unbalanced conical waves ideal for applications such as laser micro-machining, laser writing of channel waveguides, charged-particle acceleration, or creation of long and stable plasma channels.

Time-gated angular-spectrum characterization of fs-beam filamentation in water

We exploited the new gated angular spectrum (GAS) technique for characterising the complex non-linear dynamics of intense fs infrared pulses underlying beam filamentation in water. The measurements allowed us to discover that the axial white-light continuum and the off-axis coloured conical emission (CCE) are generated by different temporal portions of the light filament, the red and blue-shifted continuum being produced at the trailing and leading edge, respectively, while CCE at the pulse center. Finally, by implementing a FROG type data analysis on the GAS scheme, we were able to retrieve the phase profile of the wave-packet too.