J. Klebniczki

Angular dispersion and temporal change of femtosecond pulses from misaligned pulse compressors

A misaligned stretcher or compressor in a chirped pulse amplification laser introduces residual angular dispersion into the beam, resulting in temporal distortion of the pulse. We demonstrate that an imaging spectrograph is capable for measuring the angular dispersion of a laser beam by an accuracy of 0.2 /spl mu/rad/nm. Using this technique, the analytical expressions of residual angular dispersion of misaligned prism and grating compressors are experimentally proved. Temporal degradations of short pulses due to angular dispersion are studied by measuring the temporal stretch of 16-fs pulses, while the issues of contrast deterioration are also discussed. It is proved that the simultaneous measurement of angular dispersion and pulse duration offers the most precise alignment procedure of prismatic and grating compressors.

Demonstration of high gain amplification of femtosecond ultraviolet laser pulses

Femtosecond pulses at 400 nm were amplified using a noncollinear optical parametric amplifier pumped by picosecond pulses at 267 nm. A flat spectral gain exceeding 3500 was achieved in single pass within the available 17 nm bandwidth of the signal pulse. The effect of pump depletion, group delay difference, and the geometry of the interacting pulses on the spectral gain are also investigated.

Optical parametric amplification of femtosecond ultraviolet laser pulses

Broad-band amplification of femtosecond laser pulses using the scheme of noncollinear optical chirped pulse parametric amplification is modeled. The effect of two-photon absorption at the pump wavelength was also taken into account. The signal pulses range from 220 to 410 nm with pump pulses at 267, 248, and 213 nm. The best four crystals chosen among 12 possible ones are BBO, KDP, CLBO, and LB4. In an experiment, 30-fs laser pulses at 400 nm were amplified in a BBO crystal pumped by 267 nm pulses, exhibiting a single pass gain of 3550. The gain was found spectrally flat within the available 17-nm bandwidth of the signal pulse.

Fluid jet with variable thickness in the range 5-20 mu m

The production of a fluid jet with a thickness variable in the range of 5-20 mu m is described. In the investigated arrangement a liquid jet flowing out of a cylindrical nozzle hits a plexiglass plate near its edge and spreads forming a very thin sheet. The thickness can be easily varied by changing the angle between the nozzle and the plate. Using a dye solution in this set-up, a short-cavity dye laser of length 15 mu m has been constructed.

Travelling-wave amplified spontaneous emission excited in a prismatic geometry

A new experimental realisation of the travelling-wave amplified spontaneous emission (TWASE) is described utilising a prismatic arrangement to get the pulse front delay in the pump beam. Rhodamine dye solutions were pumped by the amplified 25 ps long 555 nm pulses of a distributed feedback dye laser. The pulse shortening in the TWASE resulted in 12 ps output pulses with 18% energy efficiency. The observed spectrum showed numerous lines, and it contained the amplified Raman line of the pump beam. Several spots were found in the far-field zone of the generated TWASE.

Measurement of the group-delay dispersion of a pulse stretcher-compressor system with two-dimensional spectral interferometry

In this work, we present a two-dimensional extension of the stationary phase point (SPP) method which is suitable for measuring the group-delay dispersion (GDD) of a stretcher or a compressor. The light path in the chirped-pulse amplification (CPA) laser is completed to form a Mach-Zehnder type interferometer, and only the stretcher is placed in the sample arm. The recombined pulses from the interferometer are sent to the entrance slit of an imaging spectrograph. The group delay as a function of wavelength can be determined from the position of the center of the spectrally resolved interference (SRI) fringes.

Observation of the boundary wave pulse

In this paper, we illustrate the boundary (diffraction) wave pattern of a ultra short divergent laser pulse at a circular aperture according to Thomas Youngs assumptions by measuring the spectrum and the radial intensity distribution of the diffracted fs pulses behind a circular aperture.

Two-Photon-Absorption of BBO, CLBO, KDP and LTB Crystals

The two photon absorption coefficient of long BBO, CLBO, KDP and LBO samples was determined from the intensity dependent transmission in the range of 0.2 - 80 GW/cm2 using 650 fs laser pulses at 248nm.

A table-top high contrast TW laser system

The seed pulses of the laser system is generated in a Kerr-lens-mode-locked Ti:sapphire oscillator pumped with 3.2 W power of a frequency doubled cw Nd:YVO/sub 4/ laser. The produced pulses exhibit 16 fs duration at 800 nm with a mean output power of 200 mW at a repetition rate of 72 MHz. The pulses are stretched in an all reflective stretcher consisted of a pair of 1200 mm/sup -1/ gratings and a spherical mirror, which allows the spectral transmission as broad as 200 nm.

Tunable third-order dispersion of a prismatic pulse compressor

The wavelength dependent thermal refractive index provides an extra degree of freedom for the adjustment of higher order dispersion of a prismatic pulse compressor. The effect allows for fine tuning ofthe intracavity dispersion ofultrafast oscillators.