We demonstrate first results of the temperature influence on Ti: Sapphire gain properties. Wavelength tuning by over 30 nm of a cryogenically cooled Ti:Sapphire laser by crystal temperature variation (50 K to 300 K) is shown.

We demonstrated the generation of 30 μJ, 110 fs pulses tunable from 450 nm to 2500 nm using a two stage parametricgenerator. We also study unusual behavior of up-conversion in an infrared femtosecond parametric amplifier.

Sources of tunable, energetic, femtosecond pulses are of substantial interest to a variety of scientific communities. Previously, femtosecond pulses in the microjoule range were only possible through complex dye amplifier schemes. With the introduction of self-modelocked Ti:sapphire oscillators, tunable sub-100 fs pulses became available although most of the experiments ask for spectral ranges not reachable by Ti:sapphire oscillators alone. In addition to generating short pulses, Ti:Al2O3 has also been shown to be an outstanding amplifier for producing ultra-high peak power pulses. Although energies up to 1 J have been produced, the maximum repetition rate of these amplifiers is typically on the order of 10 Hz. This low repetition rate prevents the use of powerful spectroscopy techniques such as heterodyne or phase sensitive detection. We previously demonstrated multi-kHz amplification of femtosecond pulses1 wich was a first step toward the production of tunable high power pulses tunable over the whole optical spectrum. We present here a femtosecond source producing microjoules pulses tunable from 250 nm to 2 μm.

Gain guiding in an old concept used in gas lasers1,2 and semi-conductors lasers. The idea is to used the gain gradient that is established when a laser medium is pumped by another laser, to concentrate the energy on the resonator axis. This guiding effect can be used in conjunction with an unstable resonator to fill the gain region. Since there is no hard aperture the energy can be extracted efficiently, while preserving good beam quality. This type of resonator is very similar to unstable resonators using a VRM, with the difference being that the gain medium becomes a gaussian aperture which can be adjusted in size by changing the pump beam diameter. Recently, S alin and Squier3 have introduced the idea that the gain guiding effect, induced in a solid-state medium pumped by a laser beam, can be used to produce high quality beams of arbitrary large diameter from unstable resonators.

We report the use of gain guiding in a Ti:Al(2)O(3) rod to produce 150-mJ tunable pulses from a flat-flat resonator with an excellent efficiency. The output beam is Gaussian and 1.3 times diffraction limited.

We describe a Nd:YAG laser source capable of producing 0.5 J, 2 ns pilses with an average power of 100 W. This laser is diode pumped and can be used to produce high average power X-ray emission in the keV range.

A new technique producing high power single frequency pulses is presented. A Nd: YAG regenerative amplifier is used. The pulse duration is continuously adjustable from 2 to 15 nsec

In this paper we will describe the most advanced research we have conducted in the amplification of cw and femtosecond lasers using Ti:Al2O3 amplifiers. We have looked at the possibility to obtain very high gain in regenerative and multipass amplifiers. In order to find the limit of this method we have modelized the multipass amplification using a Frantz-Nodvick model [1]. To be reliable, this model needs a precise value of the saturation fluence of Ti:Sapphire. As the plublished values present a great disparity we have first measured this very important parameter. In the following paper we will present the results of this measurement. Then we will analyze the possibility of very high gain amplification in Ti:Sapphire. Experimental results using a regenerative amplifier will be presented and at last the results obtained with multipass amplifiers will be described.

We present the amplification of a continuous-wave single-mode ring dye laser in Ti:sapphire. A peak gain of 2 x 10(6) has been obtained in a passive multipass amplifier, which yielded 20-nsec pulses of 0.7-mJ energy at 780 nm. We discuss the advantages of this passive multipass amplifier in comparison with a regenerative amplifier that we have also developed. By second-harmonic generation we obtained high-peak-power UV pulses from the amplified single-mode laser.

We present differents multipass amplifiers using the titanium sapphire as the amplifier medium. These amplifiers are used to produce high peak power single mode pulses.

We report the generation of femtosecond pulses in the near infrared by passive mode-locking of a cw Rh700/HITCI dispersion-compensated ring dye laser. Pulses as short as 50 fs at 800 nm have been produced for the first time to our knowledge. Titanium sapphire multipass amplifiers have been studied to increase the energy of the pulses to the millijoule level.

Saturation fluence of Ti:Sapphire (Ti:Al2O3) is obtained using gain saturation measurements. Influence of beams spatial profiles in fitting procedures is particularly studied.