G. Taft

Pulse evolution in a broad-bandwidth Ti:sapphire laser.

We demonstrate that by operating near the zero second- and third-order dispersion point in a self-mode-locked Ti:sapphire laser we can generate sub-10-fs pulses. Our numerical simulations show that the pulse duration is limited by fourth-order dispersion and that shorter pulses will be possible if this can be reduced. Also, by inserting a pellicle in various positions in a Ti:sapphire cavity, we have measured the intracavity pulse duration and chirp of the circulating pulse in the laser. Our results demonstrate that the pulse is shortest near the middle of the laser crystal, in one direction of propagation. In the other direction of propagation, the pulse is positively chirped and several times longer.

16-fs, 1-μJ ultraviolet pulses generated by third-harmonic conversion in air

We describe a simple method for generating sub-20-fs ultraviolet light pulses with useful average powers, using a kilohertz Ti:sapphire laser system. By focusing a 22-fs, 1-mJ laser pulse in air, we obtain ultraviolet pulses with an energy of 1 microJ and at a wavelength of 266 nm and with an average power of 1 mW. The pulse duration of the ultraviolet pulses was measured to be 16 fs with frequency-resolved optical gating.

Molecular engineering of polymer films for amplitude and phase measurements of Ti:sapphire femtosecond pulses

Using second-harmonic frequency-resolved optical gating and a tricyanovinylaniline polymer thin film, we have measured the amplitude and the phase of mode-locked Ti:sapphire laser pulses as short as 13 fs. These thin films are ideally suited for ultrashort-pulse diagnostics because they eliminate the angle tuning associated with birefringent phase-matched crystals, minimize pulse distortions introduced by group-velocity dispersion, and exhibit excellent photochemical stability.

Measurements of ultrashort optical waveforms using frequency-resolved optical gating

The intensity and phase of the approximately 10 femtosecond pulse from a self-modelocked Ti:sapphire laser was reconstructed using frequency-resolved optical gating (FROG). Our results verify recent models which show that uncompensated higher-order dispersion in the laser cavity is the main limitation on pulse duration.

Kerr-Lens Modelocked Ti:Sapphire Laser Oscillator Directly Pumped with Blue Diodes

We describe a Ti:sapphire laser pumped directly with 445nm laser diodes. With 70 mW average power at 800 nm and bandwidth for <13 fs pulses, Kerr-lens-modelocked pulses are available with dramatically decreased pump cost.

Molecular engineering of nonlinear optical polymer thin films for ultrashort optical pulse diagnostics

We discuss the molecular engineering of a second order nonlinear optical (NLO) polymer materials specifically for ultrashort optical pulse diagnostics. We use second harmonic generation (SHG) frequency resolved optical gating (FROG) to measure the amplitude and phase of an ultrashort pulse. It is shown that thin poled TCV/PMMA are sufficiently nonlinear and robust to be used in Ti:Sapphire ultrashort pulse diagnostics. Since such thin NLO films are not limited by phasematching they hold great promise for extremely short pulse diagnostics.

13 fs Frequency-Resolved Optical Gating Measurements with Thin Poled Nonlinear Polymers

Poled nonlinear polymer films are used to perform second harmonic frequency resolved optical gating measurements on 13fs pulses, eliminating the need for phase matched crystals.

Temporal characterization of ultrashort high-power laser pulses

Full characterization of the electric field amplitude and shape of an ultrashort optical pulse is important for a number of fields of research, such as high-field atomic and plasma physics, and the generation of ultrashort-pulse XUV and soft x-ray radiation. We have used the technique of frequency-resolved optical gating (FROG) to characterize low-energy pulses as short as 13 fs duration, and high peak-power pulses as short as 25 fs. We discuss experimental considerations for implementing FROG for very short pulses, and the limitations of the technique.

Recent advances in femtosecond laser technology: capabilities and limits

In the past five years, there has been a revolution in the field of ultrafast laser technology. Femtosecond lasers are now simple and turn-key, with output powers orders of magnitude higher than were available only a decade ago. Nonlinear frequency conversion techniques can be used to generate femtosecond pulses through the visible and infrared, and high field effects allow this range to be extended to the far-IR and x-ray regions of the spectrum. New measurement techniques have also been devised, which can extract the complete waveform of a femtosecond pulse, allowing the complete determiniation of both the amplitude and phase of pulses as short as only a few optical cycles. Finally, the pulse generation mechanisms close to the fundamental limits of operation of these systems have been understood.