In this work we combine elements of chirped pulse amplification (CPA) techniques, now familiar in solid-state lasers, with an amplifier based upon a seeded free-electron laser (FEL). The resulting device would produce amplified pulses of unprecedented brevity at wavelengths shorter than can be currently obtained by any tunable laser system. We use a subharmonically seeded FEL to illustrate the ...

The Kerr-lens mode locking ability and the ultrashort pulse characteristics are analyzed numerically for the Cr-doped ZnTe, ZnSe, ZnS active media. The advantages of these materials for the femtosecond lasing within 2-3 µm spectral range are demonstrated.

The superluminal group velocity of an ultrashort optical Bessel beam pulse is measured over its entire depth of field, corresponding to approximately 2x10(4) optical wavelengths. The method used is to measure the traveling ionization front induced by the pulse.

In the last few years femtosecond optical vortex beams with different spatial distributions of the state of polarization (e.g. azimuthal, radial, spiral, etc.) have been used to generate complex, regular surface patterns on different materials. Here we present an experimental investigation on direct femtosecond laser surface structuring based on a larger class of vector beams generated by means...

The chirp of an ultrashort laser pulse can be extracted with high accuracy from a modified spectrum auto-interferometric correlation waveform by using a new time domain algorithm that allows signal averaging. We display results revealing high sensitivity to chirp even with signal-to-noise levels approaching unity. Correction algorithms have been developed to accommodate signal distortion arisin...

In calculations of ultrafast laser-induced ionization the treatment of fundamental mechanisms such as photoionization and the Kerr effect are treated in isolation using monochromatic perturbative approaches. Such approaches are often questionable for pulses of ultrashort duration and multi-chromatic spectra. In this work we address this issue by solving the quantum optical Bloch equations in a ...

PURPOSE To optimize 3D radial ultrashort echo time MRI for high resolution whole-lung imaging. METHODS 3D radial ultrashort echo time was implemented on a 3T scanner to investigate the effects of: (1) limited field-of-view excitation, (2) variable density readouts, and (3) radial oversampling. Improvements in noise performance and spatial resolution were assessed through simulation and phanto...

PURPOSE To evaluate the effects of ultrashort laser pulses from femtoseconds to nanoseconds on the retinas of live rabbit eyes and to determine the energy requirements for visible lesion development. METHODS The retinal effects of laser exposures were examined for laser exposures with pulsewidths ranging from 4 ns to 90 fs, with visible wavelengths of 532 nm for durations > 5 ps and 580 nm fo...

* Corresponding author, [email protected] ABSTRACT The objective of this research is to develop an appropriate model for simulating the transient heat transfer processes in tissue welding subject to irradiation of ultrashort laser pulses. The ultrafast laser tissue welding process is modeled in three steps. First, there is an immediate local temperature response due to radiation absorption d...