A Bismuth Oxide-based Erbium-doped fiber (Bi-EDF) is a promising optical amplifier because it exhibits broad gain bandwidth and high gain in a very short device length. In this paper, broadband Bismuth Oxide-based Erbium-doped fiber lasers (Bi-EDFLs) are reviewed including a wavelength tunable L-band passively mode-locked Bi-EDFL and a C- and L-band continuously tunable single frequency Bi-EDFL.

We demonstrate a practical ultra-fast Nd-doped fiber laser operating in the 894-909 nm spectral range, in both soliton and stretched pulse dispersion supporting regimes. Using purposely designed semiconductor saturable absorbers, a truly self-started mode-locking regime of operation with clean, transform limited pulses, was achieved.

We report here a compact diode-pumped fiber laser that represents a promising route to designing a portable picosecond light source that is rugged and compact. The laser design presented in this paper is based on a high-contrast semiconductor saturable absorber mirror (SESAM) and targets a reliable picosecond-range fiber laser. The cavity is simple, since no dispersion compensators are used, the SESAM-based mode locking mechanism is robust, and self-starting resulted in low-maintenance turn-key operation. We investigated pulse formation in a short-length fiber cavity and found that nonlinear effects in a near-resonant SESAM in combination with the large cavity dispersion are the predominant mechanism that causes self-starting and stabilization of mode-locking. The effect of the recovery time of the SESAM on the stretched-pulse width and spectrum for resonant-type absorber mirrors was also studied.

We present the investigation of the amplification of a laser diode emitting at 976 nm in a single mode ytterbium-doped fiber in order to develop a blue laser source at 488 nm by second-harmonic generation. An optimization of the non-linear frequency-doubling process is described theoretically. First results on the amplification of the laser diode are presented.

A highly efficient Yb doped double clad fiber laser, one end pumped by a 975nm diode attack source and generating up to 115.6 of CW output power at 1100nm is reported in this paper, the maximum optical-optical conversion efficiency is 79% and the slope efficiency is about 69%. The frequency doubling of the fiber laser is obtained with conversion efficiency of 6% by using PPLN as nonlinear optical material.

We examine here the lasing conditions of a Ce :LiCAF laser crystal placed intracavity with a BBO nonlinear crystal and pumped longitudinally throughout an input dichroic mirror by the 532 nm radiation of a frequency-doubled diode-pumped Nd :YAG laser. The comparison with the results obtained with an off-axis configuration shows lower laser slope efficiencies but similar laser performance in terms of threshold absorbed pump fluences (around 200 mJ/cm²). A model based on revisited spectroscopic parameters is developed to account for these laser performance.

New hybrid matrices based on silica aerogels obtained under supercritical conditions, a highly porous material with porosityt up to 90%, have been synthesized. The open porous network of the aerogel was saturated with pyrromethene dyes solved in organic mooners, and polymerization took place inside of the silica structure. The resulting polymer filled nanoporous aerogels, cast in the form of cylindrical monoliths, were used as gain media in solid-state dye lasers. Under the demanding conditions of tightly focused transversal pumping with 532 nm, 5 mJ pulses at 10 Hz repetition rate, highly photostable laser emission was obtained.

We present a diode-pumped Yb³⁺: YAl₃(BO₃)₃ (Yb:YAB) laser system and measured the polarized outputs of the CW and femtosecond mode-locked lasers with semiconductor saturable-absorber mirrors (SESAM) at the fundamental wavelength. For the CW output, polarization ratios were 88.1% and 87.2% . For the mode-locked system, polarization ratio reached 38.5%.

Q-switched and diode-pumped 2 μm solid state lasers are becoming of increasing interest for efficient pumping of mid-infrared emitting optical parametric oscillators (OPOs). In particular, Thulium and Holmium rare earths seem to be most suited for systems with high efficiency due to their long upper state lifetime. In addition, the Ho:YAG emission around 2.1 μm is not in the strong absorption spectral band of water and it is a suitable wavelength for non linear crystal pumping, such as ZnGeP₂. Several works on Ho:YAG laser end-pumped by diode-pumped Tm:YLF laser have demonstrated high power operations¹. To simplify the set-ups, experiments with Tm-Ho intracavity lasers have been done; they demonstrated a 36.5% slope efficiency². Unfortunately these set-ups³ did not allow Q-switched operations and the thermal lens in the rods led to relatively poor beam quality (M²~5-6). We designed an original intracavity configuration with a dichroic polarizing beamsplitter to decouple Tm:YLF and Ho:YAG cavities. This solution was to improve the beam quality and allow Q-switched operations. 1.9 W of 2.09 μm at the 17.3 W diodes pump level were obtained. The slope efficiency of the diode-pump to the Ho laser output and the optical-to-optical conversion efficiency achieved were respectively ~ 21.4 % and ~ 11 %. As anticipated 4, a shift of Tm:YLF emission was experimentally scaled from 1.908 to 1.953 μm which led to an efficiency decrease for the Tm laser. Unfortunately, in this intracavity geometry, Ho:YAG acted as a saturable absorber. Instead of a cw operation in free running, random Tm:YLF laser pulses of ~ 2.5 μs were observed that each resulted in an Ho pulse (~ 200-250 ns). When the acousto-optic modulator (AOM) worked, the Ho pulses did not follow the Q-switched frequency. In fact Ho emission depends on the Tm:YLF pump energy accumulated between two gates of the AOM. Some possible ways to optimize the efficiency and to avoid the passive Q-switching behaviour of Ho:YAG are tested and first results are presented in this paper.

Q-switching of mid-infrared Er:YAG laser was obtained with an electro-optical shutter. For that the LiNbO₃ Pockels cell was used in transversal quarter-wave arrangement with the Brewster angle cut faces used as a polarizer. Parameters and dependences of this Q-switched system were investigated, i.e. a pulse length and generated pulse energy, delay between switching of flashlamp and Q-switch circuit, high voltage applied on Pockels cell were measured and optimized. The resulted giant pulse length and energy was 60 ns and 55 mJ, respectively. This generated pulse was obtained for the applied voltage around 1.4 kV and for the optimum delay value 450 us. Problem of mid-infrared giant pulse delivery, which is needed for various technological applications, was solved by a specially designed cyclic olefin polymer coated silver hollow glass (COP/Ag) waveguide. Parameters of this waveguide were: diameter 700/850 um and length 1 m. The measured transmission was 74 % which corresponded to delivered intensity 86 MW/cm². Q-switched Er:YAG laser radiation in connection with this special delivery system gives a possibility of the surgical treatment in many medicine branches, for example ophthalmology, urology or dentistry.

Broadly tunable near- and mid-infrared lasers are of interest for a variety of applications including high-resolution spectroscopy, metrology, pumping of nonlinear optical frequency converters such as optical parametric oscillators (OPOs) and standoff chemical sensing. Tunable laser sources in the 2-3 um region include Cr²⁺ doped chalcogenide lasers; cryogenic systems, such as color center lasers; limited tunability devices, such as Tm and Ho lasers, gas or chemical lasers, and diode lasers; and nonlinear optical devices such as OPOs. Transition-metal-doped chalcogenide lasers are of high interest because of their high versatility, broad room-temperature wavelength tunability, high optical efficiencies, and their potential to be scaled to high powers via direct diode or fiber laser pumping. To date, continuous-wave, gain-switched, Q-switched and mode-locked laser operation has been demonstrated. Material advantages include broad absorption and emission bands, high fluorescence quantum efficiencies at room temperature, high gain cross-sections, and minimal loss mechanisms such as excited-state absorption or upconversion. Additionally, the materials can be produced by a variety of methods, including several direct growth techniques and diffusion doping. The principal material disadvantages include a relatively large change in refractive index with temperature (large dn/dT), which can induce thermal lensing, and a short, microseconds, energy storage time. In this paper we review fundamental material properties, the current state-of-the-art of continuous-wave and pulsed Cr²⁺ doped chalcogenide lasers, and recent research results.

We present here the first CW high power laser operation obtained under diode-pumping with an Yb³⁺:CaF₂ crystal. This crystal exhibits good thermo-optical properties and can easily be grown in bulk crystals or in thin films. A maximum power of 5.8 W in a diffraction limited beam has been obtained with a 5% ytterbium-doped crystal of 4 mm-long. Moreover, the laser wavelength has been tuned over 54 nm, between 1018 and 1072 nm, and the double-pass small-signal gain has been measured to be more than 1.8, showing the great potential of Yb³⁺:CaF₂ as a gain media for ultra-short pulses operation or as amplifier.

An all solid state disk laser system-named "Advanced Disk Laser (ADL)" -particularly tailored for laser induced fluorescence (LIF) in combustion processes is presented. The system currently under development comprises an Yb:YAG-seedlaser and a regenerative amplifier. Both are based on the disk laser concept as a new laser architecture. This allows a tunable, compact, efficient diode pumped solid state laser (DPSSL) system with repetition rates in the kHz region. After frequency conversion to the UV-spectral region via third and fourth harmonics generation, this laser-due to its unique properties such as single-frequency operation, wavelength tuneability and excellent beam profile-is well suited for excitation of small molecules such as formaldehyde, OH, NO or O₂, which are characteristic for combustion processes. Using the method of planar laser induced fluorescence (PLIF) we observed concentration distributions of formaldehyde in cool and hot flames of a specially designed diethyl-ether burner. The images recorded with 1 kHz repetition rate allow visualizing the distribution of formaldehyde on a 1 ms time scale. This demonstrates for the first time the usability of this novel laser for LIF measurements and is the first step towards integration of the ADL into capsules for drop towers and the international space station.

Properties of the laser operation and simultaneously stimulated Raman scattering in the new SRS-active neodymium doped SrWO₄ crystal coherently end-pumped by alexandrite 752 nm laser radiation were investigated. The maximum generated energy 90 mJ from the free-running Nd³⁺:SrWO₄ laser at 1057 nm wavelength was obtained with the output coupler reflectivity 52%. The slope efficiency reached s = 0.52, the beam characteristic parameters M² and divergence q were 2.5 ± 0.1, and 1.5 ± 0.1 mrad, respectively. Maximal output energy of 1.46 mJ for the fundamental wavelength was obtained for Q-switched Nd³⁺:SrWO₄ oscillator with a double Fabry-Perrot as the output coupler (R = 48%), and with the 5% initial transmission of LiF:F₂- saturable absorber. Up to 0.74 mJ energy was registered at the first Stokes frequency. The pulse duration was 5 ns and 2.4 ns for the fundamental and Stokes radiation, respectively. The energy of 1.25 mJ at 1170 nm was obtained for closed Raman resonator with special mirrors. For the case of mode-locking, two dye saturable absorbers (ML51 dye in dichlorethan and 3955 dye in ethanol) were used and SRS radiation in the form of pulse train was observed. The influence of the various Raman laser output couplers reflectivity as well as the initial transmissions of passive absorbers were investigated with the goal of the output energy maximization at the Stokes wavelength. In the output, the total measured energy was 1.8 mJ (for ML51 dye) and 2.4 mJ (for 3955 dye). The SRS output at 1170 nm was approximately 20% of total energy.

We report on flashlamp pumped oscillator - three amplifiers Nd:YAG picosecond laser system in which the liquid saturable dye used for passive mode locking is replaced by semiconductor saturable absorber with multiple quantum well (MQW) structure. This element placed at Brewster angle inside a laser resonator had 100 layers of absorber and therefore it has high nonlinearity and is suitable for high power Q-switched and mode locked operation. The short pulse train from oscillator contained only 5-6 pulses with total energy of 3 mJ in single transversal mode, the pulse duration was 80 ps. After amplification, the maximum energy of the pulse train was 180 mJ. In the regime of the amplification of a single selected pulse the energy on the output of the third amplifier was 50 mJ. Operation of the oscillator in active-passive regime of mode locking using an additional acousto-optic mode-locker leads to improvement of reproducibility and stability of output parameters.

An overview of the ongoing research taking place in our laboratory comparing direct and traditional pumping is given. It includes both Nd:YAG and Nd:YVO₄ pumping with either Ti:Sapphire or diode lasers as the pumping source. Latest results addressing basic quantities connected with the pump-lase cycle in Nd:YAG lasers will be presented in detail. By comparing heat generation and laser performance of Nd:YAG oscillators pumped via two channels - direct pumping to the upper lasing level at 885nm and band pumping around 808nm, it was found that the heat generated during lasing is 27% lower with direct pumping as compared to traditional band pumping. Moreover, the experimental results suggest that the coupling efficiency between the pump band and the upper lasing level is unity, and about 8% of the upper lasing level population decays via non-radiative channels.

By using laser selective excitation and low temperature time-resolved spectroscopy techniques, we have been able to experimentally identified the ion centers of tetragonal, trigonal and cubic symmetries in a low concentrated crystal as 0.03%Yb³⁺:CaF₂. This low temperature study was then completed by an analysis of the room temperature spectroscopic properties and of the laser potential of more concentrated Yb³⁺ doped CaF₂ single crystals grown in our laboratory. A laser slope efficiency of 50% with respect to the absorbed 920 nm pump power was obtained, and the laser wavelength could be tuned between 1000 to 1060 nm.

Yb:GdVO₄ laser crystals were elaborated by the Czochralski process. Thermal conductivity value was measured by photothermal analysis and reaches 8.1 and 7.1 W.m-1.K-1 along and perpendicular to the c-axis respectively. Optical spectroscopy is presented. cw laser oscillation is obtained for the first time in this material under titanium sapphire pumping at 984 nm. 420 mW were obtained for a 2% output coupler at 1029 nm. The laser wavelength can decrease to 1015 nm in thinner sample. In this case, the quantum defect is limited to 2.9 %. Thus, a new figure of merit taking into account the quantum defect is proposed. The small amount of heat release in the material gives good expectation for high power applications.

Diffusion-bonded surfaces inside a cavity usually have little effect on a laser beam when oriented perpendicular to the beam direction. They may have a severe effect on lasing efficiency and mode structure when oriented parallel to the beam. Characterization of the interface between diffusion bonded elements and the understanding of its effect on lasing is, Therefore, important. Isolating the effect of the bonding interface from effects such as an index difference between the bulks, we used bonded BK7 slabs as the bonded element. We measured the reflections arising from the bonding interface, and then put the slabs as a passive element inside a hemispherical resonator. It was found that even for similar materials, with no refraction index difference, significant reflections occur at the bonding interface for oblique angles of incidence. When put intracavity parallel to beam axis the bonded slabs caused a significant power loss and forced higher order lasing modes. The power loss depended on both, the transmission through the interface and the size of the interface cross section relative to beam diameter.

The emergence of new laser crystals has allowed crucial progress in the ultrashort-pulsed laser technology. Recently extensive researches on new Yb³⁺ doped crystals permit the development of all-solid-state femtosecond lasers. In the Yb³⁺ solid state lasers, thermo-mechanical properties plays a key role. Thermo-mechanical parameters are gathered and analyzed in the framework of simple theoretical models. Consequently, structural properties relationships could be expressed. The review of the state of the art on the Yb doped laser material for high power and ultrafast pulses generation are presented.

An experiment has been performed to analyse a nonlinear lensing effect in a flashlamp pumped Cr³⁺:LiSAF laser which has been found to be adiverging lensing effect. The latter is due to the refrctive index change which is assumed to be proportional to the excited ion population. The corresponding constant of proportionality has been measured from the time variation of the laser pulses far-field divergence.

Fiber laser for on-board Lidar applications (EDFL) are still in steadily progress. Due to limited peak power available from laser diodes at 1550 nm, Erbium Doped Fiber Amplifier (EDFA) are required. So, the design of such eye-safe laser emitters is based on an in-depth modelling of the EDFA. This paper presents a non-linear model including physical processes such as excited state absorption, pair-induced quenching and homogenous upconversion. All needed measurements have been made to fit the theoretical data without using fitting parameters. Taking into account the complex medium susceptibility of the EDFA allows us to specify precisely its behavior in wavelength, power and phase, with respect to various forms of signals used in a Doppler LIDAR. The experimental characterization of dynamic phase variations, at the output of the EDFA, has been successfully carried out, for the first time at our knowledge.

Absorption and photoluminescence spectra of Tm³⁺ and Ho³⁺ ions in LiYF₄ crystals have been investigated at various temperatures between 10 and 320 K. The photoluminescence is investigated under excitation with Xe-lamp and laser diode. In addition to blue up-converted emission of Tm³⁺ and Ho³⁺ and green up-converted Ho³⁺ emission, anti-Stokes emission bands are observed at 687 and 703 nm under excitation in the ³H₄ state of Tm³⁺ with 785 nm laser diode. These bands are observed above 200 K, and their intensities increase exponentially with increasing temperature. They are attributed to endothermic Tm³⁺ emission due to the transition to the ³H₆ ground state from the upper ³F₃ state which is thermally populated from the ³H₄ state. Discussion is given on the optical process of green up-converted Ho³⁺ emission which is generated by the 785 nm laser diode excitation.

Tm³⁺-doped glasses have two emission bands that peak around 1470 nm and 1800 nm in the near infrared, making them potentially important in the development of fiber-optic amplifiers and fiber lasers. The relative strength and the quantum efficiency of these bands depend on the glass composition as well as the active ion concentration. In this study, we have investigated the variation of the luminescence strengths as a function of glass composition and Tm³⁺ ion concentration in a new type of Tm³⁺-doped tellurite glass. In the experiments, two sets of samples with the host composition (1-x)TeO₂-(x)PbF₂ were prepared. In the first set, the active ion concentration was constant (1 mol. % Tm³⁺) and x=10, 15, 17, 20, 22 and 25 mol. %. The second set had samples with x=10 mol. % and the active ion concentration varied from 0.2 to 1 mol. %. In the experiments, absorption measurements were first made to determine the spontaneous emission probabilities of the 4f-4f transitions of the Tm³⁺ ions. The calculations were made by using the Judd-Ofelt theory. The samples were then excited with a 785-nm diode to measure the relative emission strengths of the 1470-nm and 1800-nm bands. Our results show that as the Tm³⁺ ion concentration increases from 0.2 mol. % to 1 mol. %, the ratio of the 1470-nm intensity decreases from 0.98 to 0.18 relative to that of the 1800-nm band.

For analyzing the properties of a laser, it is helpful to calculate the eigenmodes of the laser cavity. A new approach for modeling these eigenmodes is to approximate them by a finite element discretization of a 3D two-wave eigenvalue problem. In this paper, we analyze the properties of this model. First, we show that the two-wave eigenvalue problem is equivalent to an Helmholtz eigenvalue problem. Second, we analyze the stability of the finite element discretization and explain how to construct a suitable iterative solver. Numerical results are presented.

A self-organizing laser based on a single diode-pumped Nd:YAG slab with reciprocal cavity completed by dynamic holographic gratings was created and studied. The temporal dynamics, frequency spectrum and spatial characteristics of the generated beam were examined.

We present a computer numerical model (virtual sub-nanosecond laser) utilizing intracavity stimulated Raman scattering. The goal of this work is to shorten laser output pulses (for which the highly nonlinear frequency conversion process stimulated Raman scattering is used) and to obtain high efficiency (which is enhanced by placing a Raman-active crystal inside the cavity where the fundamental laser frequency intensity is maximal). The following laser components were modeled: a diodepumped solidstate laser active medium (a crystal of the Nd³⁺:YLF type), a closed cavity for a wave on its fundamental frequency with a Q-switching element and an internal subcavity with a Ramanactive crystal with controlled output coupler transmission at the Raman frequency. The model components are: a numerical integrator of a set of three rate equations (for an inverse population of the laser medium and for the number of fundamental and Stokes frequency photons), random number sources for radiation seeding, and an interactive data input interface and graphic output. A wide range of parameters was investigated and output pulses as short as 0.8 ns were found. The optimal conditions for the maximal peak power of Stokes pulses were determined and the conditions for generating pulse trains for burst laser machining were identified.

The control of thermal lensing effect is of importance to scale the output power of diode-pumped solid-state lasers. It is particularly critical for end-pumped systems. In order to reduce the thermal lensing of diode-pumped Nd:YVO₄ lasers, we use a composite structured crystal with an undoped end cap of YVO₄ attached to the Nd:YVO₄ crystal. A numerical model is setup to simulate the temperature, stress, and end bulging of the composite crystal, as well as thermal lensing. The comparisons on thermal behaviors for composite and normal Nd:YVO₄ crystals are given in the paper. A diode-end-pumped Nd:YVO₄ laser with output power of 15.6W under the pump power of 29W and optical-to-optical efficiency of 54% is demonstrated by using the composite crystal.

Laser oscillators and amplifiers based on rare-earth-doped fibers are able to generate ultra-short laser pulses in the femtosecond regime. The typical limitations of fiber-based ultra-fast systems, e.g. in pulse energy caused by nonlinear effects, can be overcome with appropriate laser designs. Then, a high spatial precision as well as a high temporal precision can be achieved in order to support nano-structuring, time-resolved spectroscopy, or frequency metrology.

We report on a diode pumped tunable Yb:glass femtosecond laser oscillator with electro-optical cavity dumping. Pulses with energies exceeding 400 nJ and peak powers of above 1MW were generated at repetition frequencies as high as 200kHz. We discuss two issues, the possibility of enhanced stability and spiking suppression by implementation of an active feedback technology. This laser forms a compact light source for various scientific and industrial applications like micromachining.

We report a highly efficient diode-pumped femtosecond Yb:KYW laser having a compact three-element resonator that incorporates a prismatic output coupler. Near-transform limited pulses of 107fs duration at a centre wavelength of 1056nm are produced at repetition pulse frequency of 294MHz by utilising soft-aperture Kerr-lens mode locking. The femtosecond operation had a mode-locking threshold at a pump power of 250mW and the laser was tunable from 1042nm to 1075nm. The optical-to-optical conversion efficiency exceeded 50% in this femtosecond-pulse regime.

Ultrafast lasers can be used to produce laser pulses with enormous peak powers and power densities. The very high peak power that can be achieved with femtosecond pulses means that in principle, nonlinear frequency conversion should be very efficient. It should be quite straightforward to use second-harmonic (SHG), third-harmonic (THG) and fourth-harmonic generation (FHG) to produce femtosecond pulses in the near- to deep-ultraviolet. We present results on a mode-locked Yb³⁺-fiber laser operating in the 980 nm spectral band. Such lasers are very attractive as a seed source for generating blue light using SHG. The laser comprised a linear fiber cavity defined by the fiber loop-mirror and the semiconductor saturable-absorber mirror (SESAM) used to self-start the mode-locking. SESAM operating in the 940-1050 nm wavelength-range comprised 26 pairs of AlAs/GaAs quarter-wave layers that form a distributed Bragg reflector with a center wavelength at about 1000 nm. The active region consists of five GaInNAs quantum wells embedded within GaAs layers. With proper alignment of the laser cavity, the laser was self-starting for pump powers above 50 mW at 915 nm. The output mode-locked pulse train at about 980 nm had an output power of 3 mW, a repetition rate of 30 MHz and pulse duration of 2.3 ps. The pulse spectrum exhibited soliton sidebands at all pump powers, confirming that the laser operates in the anomalous-dispersion regime. The time-bandwidth product was equal to 0.47, indicating that the pulses were nearly bandwidth-limited with Gaussian temporal and spectral profiles. The average value of the cavity dispersion near 1 µm, estimated from the soliton sidebands, was -1.6 ps². With a master oscillator power amplifier configuration (MOPA) more than 200 mW of the output power is expected with just two single-mode pump laser diodes.

We have developed a mode-locked diode-pumped Yb:KGW laser generating 100-fs pulses with an output power of 126 mW. The corresponding optical spectrum has a 13.4 nm FWHM bandwidth and is centred at 1037.4 nm. In the multiple pulsing regime, bound states of solitons with rotating phase difference were observed. Consecutive solitons were separated by less than 1 ps.

Efficient lasing at 1.645mm of bulk diode-pumped Er³⁺:Yb³⁺:YAG is demonstrated. The material is transversely pumped using three quasi-cw 960-nm laser-diode arrays in a simple arrangement. In free-running mode of operation, output pulse energy of 79mJ is obtained at 4.7J of incident optical pump energy. Lasing threshold lies in the range of 1.0-1.9J in long-pulse operation, depending on pumping conditions, while optical slope efficiencies of 2.2-3.4% were measured with respect to the incident pump energy. Furthermore, initial Q-switching experiments with a Co:MALO saturable absorber yielded pulses of 1.7mJ energy and 340ns FWHM duration. As the reported laser setup is also characterized by an uncomplicated and compact design, it represents a good crystalline rare-earth candidate system with superior material qualities to compete against the established glass-host materials in the eyesafe wavelength range.

Various single crystal semiconductor wafers that can passively modulate the microchip solid-state lasers were investigated. Direct laser output at eye-safe wavelengths as well as wavelength shifting from 1.06 μm to the eye-safe wavelengths can satisfactory use those single crystal passive semiconductor saturable absorbers.

V:YAG saturable absorber was used for efficient Q-switching and mode-locking of Nd:YAG and Nd:YAP flash-lamp or diode pumped lasers operating in 1.3 mm region. Crystals of Yttrium-Aluminum Garnet (YAG) doped with three-valence vanadium V³⁺ in tetrahedral position (V:YAG) were grown using of Czochralski method in reducing protective atmosphere. High purity oxides were used for crystal growth (Y₂O₃ (5N), Al₂O₃ (5N), V₂O₅ (4N)). Concentration of V₂O₅ in the melt reached up to 1 wt. %. Discs of the diameter 5 or 10 mm and of various thickness were machined from grown V:YAG crystals. The discs were both sides polished and AR coated so that minimum reflectivity at 1.08 and 1.34 microns was reached. The initial transmission of the saturable absorber was dependent on the sample's thickness and its annealing process. We report stability improvement of passively mode-locked (by these V:YAG crystals) Nd:YAP flash-lamp pumped lasers. The maximum output energy 53 mJ at wavelength 1340 nm was obtained for Nd:YAP flash-lamp pumped laser operating at repetition rate 5 Hz. Mode-locked train envelope width was measured to be 22 ns (FWHM). Individual pulses inside the train were shorter than 1 ns. Also results with composite Nd:YAG rod Q-switched by V:YAG crystal and with Nd:YAG/V:YAG monolith rod under CW longitudinal diode pumping was obtained and compared. These laser systems represent new powerfull sources in the near infrared region.

The paper describes the oscillator of a compact laser facility designed for investigating the opportunities and methods of in-lab simulation of the radiation and hydrodynamic effects, which occur during Supernova shell dispersion. The oscillator is designed as a neodymium glass laser in the self-mode-locking regime. In order to provide mode locking, it is used a thin layer of the phototropic dye solution 3274γ. Selection from the oscillation train of single laser pulse is performed by the electro-optic Pockels cell with the DKDP crystal and multi-layer dielectric polarizer. The cavity dumping system is controlled by the electronic units. The duration of a single pulse at the oscillator output does not surpass 500 ps, while its energy reaches 1.5 mJ.

Passively mode locked ring vanadate laser pumped by 1 W laser diode was developed. Laser threshold for free running regime was 55 mW, the bidirectional mode locked operation was obtained for incident pump power of only 630 mW. The repetition rate of the laser was 226 MHz, pulse duration 53 ps. New saturable absorber and configuration with two lenses inside the resonator improved stability of mode locking regime.

This paper presents experimental results on nonlinear refraction, nonlinear absorption and optical limiting in photrefractive crystals Bi₁₂SiO₂₀ (BSO) and Bi₁₂GeO₂₀ (BGO) at the fundamental and second harmonic wavelengths of picosecond Nd:YAG laser radiation. It is shown that nonlinear refraction was due self-focusing process when nonlinear absorption was due to three-photon absorption at the wavelength of 1064 nm and two-photon absorption at the wavelength of 532 nm.

It is described the amplifier of a compact laser facility designed for investigating opportunities and methods of in-lab simulation of the radiation and hydrodynamic effects, which occur during Supernova shell dispersion. The amplifier is assembled as a 7-pass layout with spatial separation of the beams in one active element made from neodymium glass. In order to enhance the contrast of the laser pulse directed onto the target with a sophisticated design, an optical shutter is placed at amplifier input. The optical shutter is designed around an electro-optic deflector with the crystal LiTaO₃ and a spatial filter. The electro-optic deflector is controlled with the electronic units using high voltage light-triggered silicon switches. The contrast of a single laser pulse at the amplifier output is ~ 10⁴, while its energy reaches 1.8 J in case of the duration of not more than 500 ps.

New analogs of the commercial dye Pyrromethene 567 (PM567), where the chromophore core is maintained but different substituents are introduced in position 8, have been synthesized, and their lasing properties when incorporated (dissolved or copolymerized) in polymeric matrices, using both linear and crosslinked polymers with different degrees of functionalization, have been studied. In general, the new materials exhibited laser emission with efficiencies and photostabilities much higher than those of the commercial dye PM567, demonstrating that by incorporating adequate chemical modifications in teh dipyrromethene.BF₂ complexes, and selecting the appropriate polymeric formulations, efficient and photostable solid-state dye lasers competitive with their liquid counterparts can be developed.

Optical spectroscopy and Raman spectroscopy have been used to investigate Yb³⁺-doped yttrium, lutetium and scandium oxyorthosilicate crystals (Y₂SiO₅ (YSO), Lu₂SiO₅ (LSO) and Sc₂SiO₅ (SSO)). Yb³⁺ Energy levels diagram are presented. In the three hosts, Yb³⁺ ions experience high crystal field strength, particularly in Yb:SSO. Absorption and emission cross sections are presented giving insight of the laser potentials of these hosts. As Yb:YSO has already presented very good laser performances, it appears that the Yb:LSO which presents comparable spectroscopic parameters is also an attractive host for laser oscillation in the 1 um laser range.

LIL and LMJ are two French high power lasers dedicated to fusion and plasma experiments. One of the main issues of these lasers is the beam amplification that is achieved by large glass slabs (Nd doped phosphate glass). We have determined several fundamental parameters of this laser glass. In order to avoid non-linear effects during beam propagation, the spectrum of the pulse is broadened. When the spectrum is not amplified symmetrically, temporal modulation appears in the pulse. As we need to accurately center the wavelength of the laser pulse in the amplifier material gain curve, we have achieved precise measurements of its fluorescence spectrum. To predict the behaviour of the laser glass for short pulses, we have determined the sublevels structure of the laser transitions. We have also made a Judd-Offelt analysis to calculate the emission cross-section of Nd³⁺ in this glass. Finally, we have developed an experimental setup to measure the fluorescence decay which is related to glass manufacturing. We obtained an accuracy close to 1 μs (for the fluorescence lifetime at 1/e).

A diodes pumped high average power Nd:YAG rod E-O Q-switched MOPA system was designed, fabricated and tested. The laser achieved a maximum average power of 600W in a near top-hat beam with the repetition rate of 500Hz, pulse width of 15 ns. Three different type diode pump laser module with the pump power of 500W, 6.5kW and 12kW were successfully developed for master-oscillator and amplifiers. The modules have an efficient absorption of the pumped light and homogeneous pump beam distribution in the laser medium.