R. Ell

Generation of 5-fs pulses and octave-spanning spectra directly from a Ti:sapphire laser

Spectra extending from 600 to 1200 nm have been generated from a Kerr-lens mode-locked Ti:sapphire laser producing 5-fs pulses. Specially designed double-chirped mirror pairs provide broadband controlled dispersion, and a second intracavity focus in a glass plate provides additional spectral broadening. These spectra are to our knowledge the broadest ever generated directly from a laser oscillator.

Ultrabroadband double-chirped mirror pairs for generation of octave spectra

The problem of matching double-chirped mirrors to the ambient medium, which currently limits the design of ultrabroadband dispersion-compensating mirrors is reconsidered. A design of double-chirped mirror pairs that exhibit high reflectivity and a controlled group-delay dispersion in combination over 1 octave is presented. These mirrors permit the generation of octave-spanning spectra directly from a Ti:sapphire laser oscillator.

Two-dimensional spectral shearing interferometry for few-cycle pulse characterization.

We present a new method for measuring the spectral phase of ultrashort pulses that utilizes spectral shearing interferometry with zero delay. Unlike conventional spectral phase interferometry for direct electric-field reconstruction, which encodes phase as a sensitively calibrated fringe in the spectral domain, two-dimensional spectral shearing interferometry robustly encodes phase along a second dimension. This greatly reduces demands on the spectrometer and allows for complex phase spectra to be measured over extremely large bandwidths, potentially exceeding 1.5 octaves.

Self-Referenced 200 MHz Octave-Spanning Ti:Sapphire Laser with 50 Attosecond Carrier-Envelope Phase Jitter

Carrier-envelope phase stabilization of a 200MHz octave-spanning Ti:sapphire laser without external broadening is demonstrated. The individual comb lines spaced by 200MHz can conveniently be resolved using commercial wavemeters. The accumulated in-loop carrier-envelope phase error (integrated from 2.5 mHz to 10 MHz) using a broadband analog mixer as phase detector is 0.117 rad, equivalent to 50 attosecond carrier-envelope phase jitter at 800 nm.

Controlled waveforms on the single-cycle scale from a femtosecond oscillator

We present an octave-spanning Ti:sapphire oscillator supporting Fourier-limited pulses as short as 3.7 fs. This laser system can be directly CEO-phase stabilized delivering an average output power of about 90 mW with a pulse duration of 4.4 fs. The phase-stabilization is realized without additional spectral broadening using an f-2f interferometer approach allowing for full control of the electric pulse field on a sub-femtosecond time-scale.

Prism-based pulse shaper for octave spanning spectra

We demonstrate a prism-based pulse shaping setup that enables the shaping of ultrashort pulses with octave-spanning spectra. In contrast to gratings prisms allow for a high throughput and large bandwidths. The second-order dispersion of the prism material is precompensated by a fused silica prism sequence while higher dispersion orders are compensated by the pulse shaper. This flexible tool for dispersion compensation enables us to generate the shortest pulses ever achieved directly from an oscillator. The resulting pulse is almost transform-limited and shows a clean temporal profile with very low background. We assess the performance and limitations of the setup both experimentally and by theoretical analysis.

Diode-pumped 10-fs Cr3+: LiCAF laser

We demonstrate 10-fs pulses from a diode-pumped, soft-aperture Kerr lens mode-locked Cr3+:LiCAF laser with a spectral bandwidth of 150 nm and 40 mW of output power at a repetition rate of 110 MHz. For dispersion compensation, double-chirped mirrors and prisms are used. The pulses are characterized by use of spectral shearing interferometry.

Spectral phase control and temporal superresolution toward the single-cycle pulse

The concept of temporal superresolution is applied to optical few-cycle laser pulses for the first time to our knowledge. Pulse durations of as little as to 3.7 fs, well below the Fourier limit, are achieved by pulse shaping of an octave-spanning Ti:sapphire oscillator spectrum. Our prism-based pulse shaper also enables us to generate a manifold of well-controlled pulse sequences that are important for coherent control applications on a femtosecond time scale.

Two-dimensional spectral shearing interferometry (2DSI) for ultrashort pulse characterization

We present a new pulse characterization method based on two-dimensional spectral shearing interferometry with zero delay. It features simple calibration, greatly relaxed spectrometer resolution, and is well suited for few-cycle laser pulses.

Carrier-envelope phase control by a composite plate

We demonstrate a new concept to vary the carrier-envelope phase of a mode-locked laser by a composite plate while keeping all other pulse parameters practically unaltered. The effect is verified externally in an interferometric autocorrelator, as well as inside the cavity of an octave-spanning femtosecond oscillator. The carrier-envelope frequency can be shifted by half the repetition rate with negligible impact on pulse spectrum and energy.