We report on a Ti:sapphire amplifier system which produces 21 fs, 1 mJ pulses at 1 kHz. A nanojoule-level seed pulse makes 8 passes through a highly doped Ti:sapphire crystal for a total gain of approximately 106. The crystal is pumped with 12 mJ of 527 nm light which is converted into amplified pulse energy with an efficiency exceeding 10%. We have used this laser system to generate ultra-short UV light pulses through third harmonic generation. By focusing the 21 fs pulses in argon and other gases (including air), we obtain UV pulses with energy 1 (mu) J and wavelength 267 nm. The duration of the UV pulses was measured to be approximately 16 fs, representing the shortest pulses in this wavelength range measured to date.
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.
Advances in femtosecond laser technology now make it possible to reliably generate laser pulses in the terawatt energy range with 20 fs pulse duration, using laser system which fits on a single optical table. We have demonstrated two such systems: a 10 Hz, 3 TW sysetm, and a 1kHz, 0.05 TW system. These lasers make possible new studies of strong-field laser-matter interactions, and the generation of reliable femtosecond pulsed soft x-rays.
We have demonstrated a simple multipass amplifier system that generates pulses as short as 26 fs in duration, with an energy of > 60 mJ per pulse. The design minimizes higher-order dispersion and spectral distortions, and results in a near-transform limited 2 TW peak power output.
Using chirped-pulse amplification in Ti:sapphire, we have generated pulses of 21 fs duration at an energy of 0.5 mJ. We have also demonstrated further amplification of chirped pulses to 45 mJ with a bandwidth capable of supporting 25 fs pulses. The amplifier design minimizes material path-length, spectral distortion and clipping, and compensates for higher-order dispersion by using a combination of prisms and diffraction gratings.
By optimizing the intracavity dispersion compensation in a self mode-locked Ti:sapphire laser, we have generated pulses of less than 11 fs in duration. Dispersion within the laser cavity can be reduced by using a short highly-doped Ti:sapphire crystal and a prism glass which reduces third-order dispersion. Amplifier design which reduce third order dispersion have also been tested, and we have demonstrated stretching an 11 fs pulse by a factor of 1000, followed by recompression of 20 fs pulse duration. Our results demonstrate that the exceptionally broad bandwidth of Ti:sapphire can be utilized to generate pulses shorter than has been possible with any other type of laser material to date.
In this paper, we present results on the generation of 10.9 fs duration pulses directly from a self mode-locked Ti:Sapphire laser. Ultrashort-pulse operation of the laser was obtained by optimizing the intracavity dispersion compensation. A short, highly-doped Ti:Sapphire crystal and fused silica prism pair were used to achieve this. We also present preliminary results on frequency doubling of the 800 nm fundamental beam, both inside and outside the laser cavity. Detailed calculations have been made on a number of nonlinear crystals to determine the optimum crystal choice. Our calculations indicate that intracavity doubling should lead to the generation of sub-20 duration ultraviolet pulses.