We report on passively mode-locked think disk lasers with up to 60 W average power, nonlinear pulse compression to 33 fs with 18 W average power, and a fiber-feedback parametric oscillator generating 15 W in the 1.5-μm region.

With the goal to set up a high average power Diode Pumped Solid State Laser (100 Joules/10 Hz/10 ns), the Laboratory for Use of Intense Laser (LULI) is now studying various solutions concerning the amplifier medium, the cooling, the pumping and the extraction architectures. In this paper, we present the last states of these developments and the solutions already chosen.

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. Several works on Ho:YAG laser end-pumped by diode-pumped Tm:YLF laser have demonstrated high power operations. To simplify the set-ups, experiments with Tm-Ho intracavity lasers have been done; they demonstrated a 36.5% slope efficiency. Unfortunately these set-ups did now allow Q-switched operations and the thermal lens in the rods led to relatively poor beam quality (M² ~ 5-6). We design an original intracavity configuration with a dichroic polarizing beamsplitter to decouple Tm:YLF and Ho:YAG cavities. This solution improves the beam quality and allows Q-switched operations. We obtained 1.9 W of 2.09 μm at the 17.3 W diodes pump level. The slope efficiency of the diode-pump to the Ho laser output and the optical-to-optical conversion efficiency achieved are respectively ~ 21.4% and ~ 11%. As anticipated, we experimentally scaled a shift of Tm:YLF emission from 1.908 to 1.953 μm that leads to an efficiency decrease for the Tm laser. In this intracavity geometry, Ho:YAG acted as a saturable absorber. Instead of a cw operation in free running, we observed random Tm:YLF laser pulses of ~ 2.5 μs that each resulted in a 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. Possible ways to optimize the efficiency and avoid the passive Q-switching behaviour of Ho:YAG are suggested.

We demonstrate a highly efficient and low threshold passively mode-locked femtosecond Yb:KYW laser pumped by an InGaAs narrow-stripe laser diode and which incorporates a semiconductor saturable absorber mirror. Near-transform limited pulses of 123fs at 1047nm were produced at an average mode-locked power of 107mW for only 308mW of incident pump power. An optical-to-optical conversion efficiency of 35% was achieved and the corresponding electrical-to-optical efficiency exceeded 14%.

We present the results of experimental investigation of laser-diode bars side-pumped Nd³⁺:KGd(WO₄)₂ (KGW)-laser with self-conversion of laser wavelength at 1351 nm to the first Stokes component 1538 nm.

Q-switch performance of YAG:Nd at the wavelength of 1.32 μm under 2 W laser diode pumping has been studied using plane-plane and confocal resonator configurations. YAG:V³⁺ passive shutter has been applied. The pulse train with frequency 17 kHz and pulse duration of 8 ns have been obtained. An overage power of 430 mW and 160 mW were achieved in CW and Q-switch modes respectively, peak power in Q-switch mode being of 700 W.

Slowly opened Q-switch modulation superior in giant pulse operation. All of active and passive modulators: LiNbO₃-Plastic Dye Sheets-LiF:F₂-Cr⁴⁺:YAG-RG1000 Color Filters-InP and GaAs semiconductor slabs have been investigated and analyzed. Diode-pumped microchip all solid state lasers using the above passive modulators are demonstrated respectively..

It has been established, for the first time, that the shift of luminescence of Cr³⁺ ions in forsterite from 900 to 950 nm (FWHM~240 nm) occurs gradually as the Li-codopant concentration is increased. Selectively excited polarized luminescence at 300 and 77 K is used to interpret the nature of the emitting Cr³⁺ centers. The features of the observed spectra can be explained by replacement of the initial Cr³⁺ centers by Cr³⁺-Li associates. The red shift of the Cr³⁺ luminescence peak and simultaneous reduction of the Cr²⁺ ions content are shown to be promising for the development of a tunable Cr³⁺-forsterite laser.

Glasses based on the lanthanum borate (La₂O₃ • 3 B₂O₃) with total rare-earth concentration up to 40 mol.% were sintered. Spectroscopic properties of glasses (Yb⁺³ concentration 1-15 at. %) were investigated. Absorption and fluorescence spectra as well as fluorescence decay kinetics for all compositions had been measured.

An enormously high concentration of Cr³⁺-Cr³⁺ and Ho³⁺-Ho³⁺ dimers is found in synthetic forsterite doped by Cr or Ho ions, respectively. The measurements were performed by means of high-frequency two-dimensional EPR spectroscopy in the frequency region of 65-250 GHz at 4.2 K in magnetic fields up to 0.8 T. The analysis of the spin Hamiltonian parameters and rotational diagrams showed that the Cr³⁺-Cr³⁺ dimers are formed by a pair of Cr³⁺ ions with an Mg²⁺ vacancy between them replacing three Mg²⁺ ions in M1 positions situated in a quasi-one-dimensional chain aligned parallel to the crystal c-axis. It is found that the interaction between Cr³⁺ ions in the dimer is the ferromagnetic exchange with parameters J_z = 0.47 GHz and J_t = 0.79 GHz. Most probable structures of Ho³⁺-Ho³⁺ dimers consist of two Ho³⁺ ions coupled by the dipole-dipole interaction (J_z = 11.4 GHz) and situated in the M2 octahedral positions in the same bc-layer with a Mg²⁺ vacancy in the M1 position between them. The mechanism which favors the formation of dimers of trivalent impurity ions in forsterite is proposed. It is connected with the conservation of the overall charge balance under the substitution of three nearest neighboring Mg²⁺ cations by the two impurity ions with a Mg vacancy between them.

The laser characteristics of Cr²⁺:ZnSe single crystal produced by a seeded physical vapor transport method were investigated. The free-running laser action centered at 2.45 µm with the quantum slope efficiency of 87% was demonstrated under pumping by the 1665 nm output of Co:MgF₂ laser.

New potential ytterbium-doped laser crystals-disordered scheelite-like double sodium-gadolinium tungstate NaGd(WO₄)₂ and sodium-lanthanum molybdate NaLa(MoO₄)₂, had been grown by Czochralski technique. Polarized absorption and fluorescence spectra as well as fluorescence decay kinetics had been measured for these crystals, doped with Yb³⁺ ions. Gain cross-section for different population inversion of ²F₅/₂ level had been calculated.

Absorption and emission spectra of Yb³⁺ in yttria-stabilized cubic zirconia were studied. Selective emission spectra of Yb³⁺ in crystal ZrO₂-O,3% Yb₂O₃ 12% Y₂O₃ at wavelength scanning the exciting light in the absorption band range were registered. Emission spectra of Yb³⁺ with 3 ms and 5 μs time-delay relation to excited pulse were also obtained for the crystal. The results of the carried out experiments are discussed within assumption frame of existing three basis types of optical centers.

The paper reports the experimental results on the temporal characteristics of coherent stimulated emission on the ³P₀-³H₆ transition of Pr³⁺ ion dopped into the LaF₃ matrix while tuning of pumping frequency in the vicinity of the ³H₄-³P₀ transition. The generation pulse duration was found to be about 10 ns, and it was delayed by 3-4 ns relative to the beginning of the pumping pulse at the exact resonance. It was observed that as the detuning increased, the shape of the coherent stimulated emission pulse changed and its delay increased up to 10ns. A theoretical interpretation of the experimental results observed is proposed.

Method for measuring nonlinear refractive index (n₂) of optical materials is presented. It is based on the analysis of large scale beam distortions caused by the nonlinear aberrational lens induced by power radiation in the medium under study. Absolute n₂-values for new Russian laser phosphate glass KGSS 0180/35 (n₂ ≈ 1.2•10^-13 CGSE units) and widely used glasses GLS 22 (n₂ ≈ 1.9•10^-13 CGSE units) and K8 (n₂ ≈ 1.4•10^-13 CGSE units) were obtained with this method for laser pulse duration of 4 ns. Also, evaluation of nonlinear phase delay induced in the laser beam that has passed through the glass samples under study for a longer pulse duration of -up to 25 ns has been performed.

At the recent years a technology of ceramic laser media on the base of crystals with a cubic symmetry has been developed. The perspective of the usage of ceramic materials in many different applications including high-power short pulse lasers stimulates the work on the systematic study of the properties of these new laser media. In this report a nonlinear refractive index, n₂, was studied for several garnet and sesquioxide laser ceramics using Z-scan method. This technique with a “top-hat” probe beam intensity distribution was used. Nonlinear indices in the range of (2-6)x10^-13 were measured for YAG, Y₂O₃, Lu₂O₃, and Sc₂O₃ ceramic samples. These data together with the laser and spectroscopic parameters of several Nd³⁺ and Yb³⁺ doped crystals of a cubic symmetry were used to estimate in the complex the properties of laser ceramics for the application in high-power pulsed-repetitive laser-drivers for inertial confinement fusion (ICF) program. A high heat conductivity of ceramic materials is a profitable characteristic for this application as compared to glasses which are used now for experiments in ICF at single shots regime. Compared to single crystals, ceramic elements provide laser designers with a variety of new design options for the projects of laser-drivers. The usage of ceramic active elements with low and increased n₂ values in the channels of a powerful laser facility is discussed.

This work presents a method for determination of specific amplification coefficient for stimulated Brilloin scattering (SBS) of radiation based on measuring amplification of the Stokes signal in a medium sample used as the SBS-amplifier. Registration of spatial distributions of amplified beam intensity allows minimization of a measurements error caused by saturation of Stokes radiation amplification in the sample under study. Values of specific amplification coefficient for SBS of radiation are obtained under identical experimental conditions for new phosphate glass KGSS 0180 (g = 1.9 cm/GW) and for glasses widely used in laser systems: GLS 22 (g = 1.4 cm/GW) and K 8 (g = 1.3 cm/GW). By means of optical heterodyning of radiation a SBS-frequency shift of laser radiation at a wavelength of 1.054 microns is measured for new glass KGSS 0180 (▵v = 14.57± 0.02 GHz). It makes it possible to estimate hypersound propagation velocity in the tested glass (V ≈ 5030 m/c) at this frequency.

The functional lifetime of large aperture optical components used in high power lasers, like LIL and LMJ facilities, is mainly determined by laser damage measurements. We present experimental procedures and statistical analysis, made on small samples with mm-size beams, to determine damage densities and damage growth laws. The tests and analysis are compared to other results obtained with larger beams (few cm²) on large aperture components.

The research results of possibility of laser generation and amplification in Nd-doped YLF crystals on the transition ⁴F_3/2-⁴I_13/2 in the region of 1.3 μm are presented in this report. The possibility of wavelength control in the range 1.3136-1.3157 μm is demonstrated experimentally. The gain coefficient for iodine photodissociation laser wavelength λ=1.3152 μm in the crystal with 60 mm length is about 0.06cm^-1. The generation in the mode-locked regime with wavelength ~ 1.3 μm is obtained. The duration of pulses in the train does not exceed 800 psec.

Q-switched laser behavior of the new IRE RAS developed Yb-Er phosphate glass LGS-KhCh2 was studied using FTIR and water-cooled chamber with lamp pumping. Laser rod near 3 mm in diameter and 80 mm long was investigated. Laser output of 5-10 mJ was achieved at 1535 nm at 20 Hz repetition rate. For the first time, to our best knowledge, the CW operation of the erbium glass laser under lamp pumping is demonstrated.

Schemes are considered for the construction of radiation balanced and self-cooling lasers. The formula is obtained for the photon number of self-cooling laser with direct and up-conversion energy transfer in its generation field, their intensity of radiation and conditions of their realization are determined. Its advantages are discussed comparing with traditional laser.

Resonance periodical structures were found to have the one uniformly distributed mode. The difference between this mode gain and all the others modes gain is independent from the number of channels, while it is smaller, than the obtained critical value.

We describe the linear and nonlinear transfer characteristics of a multi-resonance optical device consisting of two ring resonators coupled one to another and to a waveguide. The propagation effects displayed by the device are compared with those of a sequence of a waveguide-coupled fundamental ring resonators.

Thin films of molecular J-aggregates of polymethyn dyes were obtained. Linear and nonlinear optical properties of the films were investigated. These thin films of J-aggregates were successfully used as saturable absorbers for passive mode-locking in YAG:Nd³⁺ laser for the first time. The reproduced generation of ultra short pulses with a duration of ~13 ps was obtained for two types of dyes forming the J-aggregates.

Second harmonic energy conversion efficiencies in KTP and BBO crystals have been investigated by using pico-second pulse. For extracavity-doubled, conversion efficiencies 43.8% and 32% were obtained, respectively. In intracavity-doubled, efficiencies 53.4% and 70% by using convex-ARR (Anti-resonant Ring) unstable resonator, 60.2% and 80.6% by using unstable confocal resonator were achieved, respectively. It shows that KTP crystal has higher conversion efficiency at lower intensity (under KTP gray-tracking threshold) and lower efficiency at high power laser compared to the BBO crystal. This result principally caused by the KTP gray-tracking phenomena.

Laser power enhancement cavities are usually applied for frequency doubling of continuous radiation in nonlinear crystals, because of relatively small available CW power. Besides, external cavities allow to produce single-frequency radiation. Four- or three-mirror ring cavity design with two focusing mirrors is usually used in experimental and theoretical studies as well as in applications. In these schemes the first curved mirror focuses a relatively wide beam into nonlinear crystal and the second one reproduces the original beam from divergent one, which comes out of the crystal. We propose the three-mirror cavity design with single curved mirror, which is used both for focusing and reproducing of the beam. Two additional flat mirrors allow to direct the beams into the crystal from and back to the focusing mirror and thus to close the ring cavity of triangle form. Calculations show that stability of the single-focusing-mirror cavity has larger tolerance for angles of the beam incidence at the curved mirror in comparison with traditional schemes and broader stability region. It is analogous to a two-mirror concentric cavity, but has advantages of a ring cavity at the same time. The compact cavity is experimentally realized for frequency doubling of 488 nm argon laser single frequency radiation in BBO crystal. Power enhancement achieved in the cavity is about 30 times. Thus 244 nm second harmonic power of 33 mW at 660 mW pump power is produced having about 10 m coherence length.

A theoretical model that describes second harmonic generation of focused ultrashort pulses in the presence of large group velocity mismatch (GVM) is presented. We observe a direct dependence of the optimal focusing on the strength of GVM. Our model also describes the temporal duration of the second harmonic pulsed under these conditions as well as the change in optimal phase mismatch. The theoretical results are compared with an experiment for second harmonic generation with focused femtosecond pulses in a “thick” crystal of KNbO₃ with a length much bigger than the time duration-GVM ratio.

The second harmonic generation, which appears upon optical poling of a bulk glass have been investigated theoretically and experimentally. The existence of two-beam generation pattern has been shown and peculiarities of the kinetics of process have been studied in oxide glass.

The development of compact high efficiency optical parametric oscillators (OPO) which generate widely tunable coherent radiation with small divergence and high angular pointing stability is a currently a topical problem. In the past, many efforts have been made to reduce the spectral bandwidth and the divergence of the OPO output beam. The spatial and spectral properties of a 355nm pumped pulsed ns-BBO OPO were improved by using type II phase matching and pump beam back reflection. In this way the OPO bandwidth was reduced by more than a factor of 20 to less than 0.1nm, and the divergence of the OPO beam was reduced in the phase matching plane by a factor of 5 to 1mrad. We investigated the spectral properties of the type II BBO OPO and KTP OPO pumped at 532nm and pump beam reflected. It was found, that the OPO bandwidth was reduced by more than a factor of 5 to less than 0.3nm at 680nm and 0.7nm at 1064nm. We determined, that in collinear OPO with inclined nonlinear crystal in the forward direction the output signal beam deviates from the pump beam. After reflection at the OPO out-coupling mirror the signal and pump beams inside crystal are non-collinear. After passing through the crystal in backward direction and reflection at the OPO rear mirror the signal and pump beams inside crystal are again collinear.

Optical phase locking of a diode laser to a mode of a femtosecond optical comb has been achieved with a system that joins the advantages of analog and digital phase detectors. Low noise and fast response are combined with broad phase range and lock reliability. Details of the circuit are illustrated, and properties of the different phase detectors in view of optical frequency measurements are discussed.

An heterodyne technique employing ultra-wide band Schottky diodes and a femtosecond pulsed laser was tested to perform frequency measurements in the far infrared range. Preliminary experiments demonstrate an efficient frequency down-conversion in Schottky diodes by mixing the microwave radiation with the output of a femtosecond laser used as a reference local oscillator.

We present a new laser setup suited for high precision spectroscopy on atomic strontium. The source is used for an absolute frequency measurement of the visible 5s²¹S₀-5s5p³P₁ intercombination line of strontium which is considered a possible candidate for a future optical frequency standard. The optical frequency is measured with an optical comb generator referenced to the SI through a GPS signal. We developed also an all solid state blue laser source that will be used for laser cooling of strontium, which will result in a better control on the systematic effects and a great improvement in the precision of the measurement.

Frequency shifts of the spin-forbidden ³P_j-¹S₀ transitions for Mg, Sr and Yb atoms due to external laser field are calculated, based on a combination of measured atomic parameters (transition energies) and perturbation theory. Calculations of the higher-order dynamic Stark effect have been performed in connection with precise measurements on cooled and trapped atoms and the design of the ultra stable optical clock in an engineered light shift trap. Dispersion properties of the polarizability and hyperpolarizability components and their behavior in the vicinity of both resonances and so-called “crossing points” for the upper and lower atomic states, are analyzed. The calculation of the radial matrix elements is carried out with the use of the Green’s function method on the model potential approximation. The Green’s function in this approach has a simply analytical representation and enables one obtain the matrix elements in the form of rapidly convergent hypergeometric-type series.

The effect is determined of a steady electric or/and magnetic field on coherent frequency mixing of a two-colour radiation in atoms. Analytical formulas for the cross section dependence on polarization have been derived which provide information on a possible way to determining E2/M1 amplitude ratio from the efficiency of the de-field-induced coherent process for collinear laser waves. The polarization-dependent properties of the process’ cross section are determined analytically in the case of Indium and Thallium atoms.

The polarization dependence of a two-colour frequency mixing in free atoms may be used for determining the ratio of E2/M1 contributions to an amplitude of a dipole-forbidden radiation transition. The details are presented for Indium and Thallium atoms where this ratio represents an important quantity determining parity nonconservation effects on atomic optical spectrum.

The high temporal resolution and accuracy of spectrum restoration achieved with a correlation Fourier spectrometer substantially depend on the precise knowledge of the optical characteristics of the used operating white light source. However, the beforehand calibration of this source does not guarantee avoiding of errors due to random disturbances during spectrometer’s operation. In the present work we solved two tasks. We analyzed the noise sources in a three-channel Fourier spectrometer with simultaneous recording of interferograms for the etalon light source, for the operating source and for the investigated sample using Monte-Carlo simulations. As a second task we made a prototype of a correlation Fourier spectrometer and simulated the real-time tracking of changes in autocorrelation functions of different semiconductor light sources (LD, LED and high-power LED) using the measured interferograms. We proposed an analogous feedback system to perform a current correction of the autocorrelation of the operating light source following the changes in the autocorrelation function of the etalon source.

A precise interferometric method for three-dimensional shape measurements in a wide dynamic range with double symmetrical illumination of the objects is presented. The technique proposed is especially useful for remote, non-destructive in-situ measurements of art and archaeological objects. The method is based on projection two-spacing phase-stepping interferometry. The theoretical approach, experimental results as well as a sensitivity assessment of the measurements are discussed.

To control the optical parts of a wide range, it is suggested to use an interferometer with aligned branches, which includes a series of accessory lenses. To control large-dimension parts, a spherical mirror with a compensator is used as a power component. The paper presents the main specifications and schematic diagrams of the focusing objectives as well as the variants of the zoom-lens schematics and their characteristics intended to test the large-dimension parts of plane, convex and concave shapes.

A method of characterization of thin metal film from a complex response of a scanning differential heterodyne microscope is considered. The amplitude and phase responses are related with a reflection coefficient to be depended on film parameters: a thickness and a complex refractive index. The relationship between a sensitivity of the method and characteristics of layers under the semitransparent metal film has been established. It has been demonstrated that the error of the parameter determination can be minimized by changing of the thickness of dielectric layer under the film. The thickness of Au film has been determined experimentally from amplitude response. The possibility to use a phase response of a microscope was considered. The process of further modification of the method has been proposed.

We propose and study a novel optoelectronic device for thermal characterization of materials. It is based on monitoring the photothermal deflection of a laser beam within a slab of a thermo-optic material in thermal contact with the material under study. An optical angle sensor is used to measure the laser deflection providing a simple and compact experimental arrangement. We demonstrate the principle of operation of the sensor and simple procedure that can be used to measure thermal effusivity of liquids. The proposed device could be implemented into a compact sensor head for remote measurements using electrical and fiber optic links.

Absorption spectra of atmospheric air in the 2.41-2.46 μm wavelength region are recorded by intracavity laser spectroscopy technique using a Cr²⁺:ZnSe laser. The dynamics of intracavity absorption was studied for the generation time of 0-100 μs. The experiment demonstrates that the Cr²⁺:ZnSe laser operating in the IR 2-3 μm spectral region can be utilized for high sensitivity intracavity laser spectroscopy measurements.

A lidar system based on Er-laser with eye-safe radiation (the wavelength is 1.54 mm) has been created and tested for detection of smoke and other pollution in air. Both theoretical estimations and preliminary experiments show that the needed signal registration may be possible for distances of 10-12 km depending on smoke scattering parameters.

We present a theoretical study of an erbium-doped optical fiber operating in the superluminescent regime. Experimental results for different pump power levels and fiber length show that the theoretical model could render useful information for predicting parameters such as total output power, spectral bandwidth and optimum fiber length to achieve the superluminescent regime. These types of sources could have direct application in wavelength multiplexed arrangements of fiber sensor, fiber gyroscopes or in general, in any sensors in which a broad wavelength and stable light source is required.