J. Wheeler

Intense self-compressed, self-phase-stabilized few-cycle pulses at 2 μm from an optical filament

We report the compression of intense, carrier-envelope phase stable mid-IR pulses down to few-cycle duration using an optical filament. A filament in xenon gas is formed by using self-phase stabilized 330 microJ 55 fs pulses at 2 microm produced via difference-frequency generation in a Ti:sapphire-pumped optical parametric amplifier. The ultrabroadband 2 microm carrier-wavelength output is self-compressed below 3 optical cycles and has a 270 microJ pulse energy. The self-locked phase offset of the 2 microm difference-frequency field is preserved after filamentation. This is to our knowledge the first experimental realization of pulse compression in optical filaments at mid-IR wavelengths (lambda>0.8 microm).

Strong field physics with long wavelength lasers

The generation of short, intense, mid-infrared laser pulses allows for the exploration of atom–laser interactions deep in the tunnelling regime as well as providing the ability to explore scaled interactions. In this paper we present recent experimental and theoretical results for this largely unexplored parameter space.

Strong-field physics using mid-infrared lasers

This document reports recent theoretical and experimental investigations of strong field ionization and high harmonic generation from mid-infrared lasers at 2 and 4 microns. Numerical solution of the time-dependent Schrodinger equation as well as Strong Field approximation calculations are reported. Photoelectron and high harmonic spectra are discussed. Preliminary experimental results are compared to the theoretical predictions.

High harmonic generation from long wavelength drivers

The paper reviews recent advances in high harmonic generation from mid-infrared lasers. The results emphasize the advantages of long wavelength drivers for cut-off extension, GDD reduction, attosecond pulses and reports on below-threshold and liquid harmonics.

High order harmonics from mid‐infrared drivers for attosecond physics

The generation of light pulses with attosecond (10−18 seconds) duration is studied using laser drivers operating in the mid‐infrared region. This paper first examines the fundamental principles of attosecond formation by Fourier synthesis of a high harmonic comb. Experimental demonstration of the extension of the harmonic cutoff is shown using a 2 micron driver. Then, the crucial spectral phase properties, responsible for the pulse structure on the attosecond time scale, are measured with an all‐optical technique using a mix of the fundamental pulse with its second harmonic. The expected 1/λ scaling is verified, which demonstrates a practical way towards pulses approaching the atomic unit of time (24 as).

Absolute carrier-envelope phase signature in THz emission from a femtosecond filament in argon

We report on our investigation of THz emission from femtosecond filaments in argon and propose a single-shot scheme for determination of the absolute carrier envelope phase with a 2-pi ambiguity.

Intense self-compressed carrier-envelope phase-locked few-cycle pulses at 2 µm

We demonstrate filamentation at 2 mum using carrier-envelope phase (CEP) stabilized 55 fs, 330 mui pulses from an OPA. The ultra-broadband output is self-compressed below 3-optical cycles with 270 muJ and preserves the CEP offset.