One well established and very robust way to generate few-cycle laser pulses with durations down to 1.5 cycles and mJ level energies is hollow fibre pulse compression. A laser pulse with durations around 30fs (~10 cycles) is focussed into a hollow capillary with diameters of approx 250um. During the propagation along the 1m capillary, which is filled with a gas (e.g. argon, or neon) the pulse undergoes self-phase-modulation (SPM) which generates more bandwidth. Coherent spectra covering more than one octave are possible. When engineered carefully the pulses have a smooth spectral phase, and can be compressed to near single cycle durations with chirped mirrors.
Photo of the hollow fibre and chirped mirror compressor.
Schematic of our experimental setup.
CEP stability of the compressed 1.5 cycle pulses.
A pulse measurement by attosecond streaking confirms the pulse duration of 3.53 fs (1.5 cycles).
Relevant Publications:
Witting, Tobias, Felix Frank, Christopher A Arrell, William A Okell, Jonathan P Marangos, and John W G Tisch. “Characterization of High-Intensity Sub-4-Fs Laser Pulses Using Spatially Encoded Spectral Shearing Interferometry.” Optics Letters 36, no. 9 (May 2011): 1680–82. http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-36-9-1680
Witting, T, F Frank, W A Okell, C A Arrell, J P Marangos, and J W G Tisch. “Sub-4-Fs Laser Pulse Characterization by Spatially Resolved Spectral Shearing Interferometry and Attosecond Streaking.” Journal of Physics B: Atomic, Molecular and Optical Physics 45, no. 7 (April 14, 2012): 074014. doi:10.1088/0953-4075/45/7/074014. http://iopscience.iop.org/0953-4075/45/7/074014
Okell, William A., Tobias Witting, Davide Fabris, Dane Austin, Maimouna Bocoum, Felix Frank, Aurelien Ricci, et al. “Carrier-Envelope Phase Stability of Hollow Fibers Used for High-Energy Few-Cycle Pulse Generation.” Optics Letters 38, no. 19 (October 1, 2013): 3918–21. doi:10.1364/OL.38.003918. http://ol.osa.org/abstract.cfm?URI=ol-38-19-3918 (spotlight summary: https://www.osapublishing.org/spotlight/spotlight-modal.cfm?id=267744)