K. Yamakawa

REGENERATIVE PULSE SHAPING AND AMPLIFICATION OF ULTRABROADBAND OPTICAL PULSES

Regenerative pulse shaping is used to alleviate gain narrowing during ultrashort-pulse amplification. Amplification bandwidths of ~ 100 nm, or nearly three times wider than the traditional gain-narrowing limit, are produced with a modified Ti:sapphire regenerative amplifier. This novel regenerative amplifier has been used to amplify pulses to the 5-mJ level with a bandwidth sufficient to support ~ 10-fs pulses.

Generation of 18-fs, multiterawatt pulses by regenerative pulse shaping and chirped-pulse amplification

Transform-limited, 18-fs pulses of 4.4-TW peak power are produced in a Ti:sapphire-based chirped-pulsed amplification system at a repetition rate of 50 Hz. Regenerative pulse shaping is used to control gain narrowing during amplification, and an optimized, quintic-phase-limited dispersion compensation scheme is used to control higher-order phase distortions over a bandwidth of ~100 nm. Seed pulses are temporally stretched >100,000 times before amplification.

Methods for generation of 10-Hz 100-TW optical pulses

Phase and amplitude control during multiterawatt, ultrashort-pulse amplification is discussed. Methods for efficient energy extraction and scaling to 100-TW peak powers are outlined.

Time-gated medical imaging with ultrafast laser-plasma x rays

Laser-generated, hard x-rays are produced in a > 1018 W/cm2 focus of an ultrashort-pulse laser system. The application of ultrashort-duration, laser-generated x-rays to diagnostic medical imaging is discussed. Time-gated detection allows removal of scattered radiation, improved image quality and possible reduction of patient exposure. Methods for improvement of x-ray yield, design of appropriate drive lasers, and applications to mammography and angiography are also discussed.

Techniques for controlling gain narrowing during ultrashort-pulse amplification

Regenerative pulse shaping is used to overcome gain narrowing during ultrashort pulse amplification. We have demonstrated multiple spectral filters for broadening the amplified spectrum. We have produced amplified pulses with an energy of approximately 5 mJ and bandwidths of approximately 100 nm, or nearly 3 times wider than the gain narrowing limit of Ti:sapphire.

Ultrafast x-ray absorbtion and diffraction

Our goal is to watch the evolution of matter on the atomic length scale and on the time scale on which elementary chemical reactions take place. We present initial experiments made in collaboration between UCSD and the INRS laboratory in Canada, on time-resolved ultrafast, 3 ps temporal resolution, near-edge x-ray absorption of gas phase SF6 at 2.4 keV (4.89 A). We can see both the initial presence of the F atoms around the S and their absence after photodissociation produced by pumping with an intense optical pulse. Simulations of ultrafast EXAFS and diffraction experiments are presented. We are constructing an ultrahigh intensity laser to generate ultrafast x-ray pulses from laser-produced plasmas. This laser is especially designed to achieve high average power, short pulse duration and high intensity to produce very high temperature solid density plasmas and ultrahot electrons for ultrafast hard x-ray production at high x-ray photon flux, which should enable us to perform a variety of ultrafast x-ray absorption and diffraction experiments. Finally, we discuss several means to measure the duration of subpicosecond x-ray pulses.

Ultrashort-pulse, ultrahigh-peak-power Ti:sapphire lasers

Techniques for the production of multiterawatt, sub-20-fs, optical pulses via chirped pulse amplification are discussed. Regenerative pulse shaping is used to control gain narrowing during amplification and an optimized, quintic-phase-limited, dispersion compensation scheme is used to control higher order phase distortions over a bandwidth of approximately 100 nm. Transform-limited, 18-fs pulses of 4.4-TW peak power have been produced in a Ti:sapphire- based, chirped pulse amplification system at a repetition rate of 50 Hz. Extensions to shorter durations and peak powers approaching 100 TW are also described.

Multiterawatt femtosecond lasers for high field physics

Techniques for the control of femtosecond resolution phase and amplitude distortions during the amplification of ultrashort pulses are reviewed. Applications of a 4‐TW, 30‐fs, 10‐Hz, diffraction‐limited laser system are discussed and include ultrafast hard x‐ray generation for diagnostic imaging and field‐ionization‐driven XUV lasers.

Next generation ultrashort pulse lasers: Terawatts to Petawatts

Techniques for the control of femtosecond resolution phase and amplitude distortions during the amplification of 10‐fs optical pulses to joule‐level energies are discussed.

10-fs range ultrahigh peak power lasers

The amplification of 10-fs pulses presents numerous challenges but potentially may allow relatively small laboratory systems to achieve optical powers in excess of a p eta watt at repetition rates on the order of several Hz.