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Concept of a solid-state femtosecond laser system with a multigigawatt power level in the 4–5 μm range has been proposed. The system contains an ultrashort pulse seeder, a two-stage chirped pulse amplifier based on a broadband Fe2+:ZnSe active element with optical pumping by a YSGG:Cr:Er laser, and an output stage that provides additional nonlinear optical compression of an amplified pulse to approximately 30 fs in a dielectric CaF2 medium with anomalous group velocity dispersion in this spectral range.

A room-temperature laser based on a single crystal has been studied. The crystal was pumped by a nonchain electric-discharge HF laser with a light pulse FWHM of . The pump spot diameter on the crystal surface varied from 3.9 to . The slope efficiency at these values of was 37% – 39 %, respectively. The maximum laser energy was (at ) with the total efficiency with respect to the absorbed pump energy of . A further increase in the laser energy was not achieved because the crystal was destroyed at an incident pump energy and power of and , respectively. The damaged region has a form of a long narrow channel shifted from the entrance surface inside the active element.

We demonstrate a first-of-its-kind efficient chirped pulse amplification of broadband mid-IR (4-5 μm) femtosecond seed pulse (230 ps, 4μJ) generated in AgGaS2 based OPA driven by Cr:forsterite laser in multi-pass Fe2+:ZnSe amplifier optically pumped by solid-state Q-switched Cr:Yb:Ho:YSGG laser (2.85 μm, 30mJ, 5Hz, 0.6 J/cm2). The system delivers 1.2 mJ at pulse duration of 230 ps. Straightforward compression to 150 fs pulse is achievable with 70% efficiency using diffraction grating pair with peak power of about 6 GW. Further non-linear compression in a bulk CaF2 due to the SPM and anomalous GVD should provide the enhancement of peak power up to 20 GW. Possible routes to reach sub-TW and even TW power level in mid-IR are discussed.

Continuous-wave lasing is obtained for the first time in a Cr2+:CdS crystal pumped by a thulium fibre laser at 1908 nm. The output power of the laser at 2534 nm achieved 0.81 W with the slope efficiency with respect to the absorbed pump power equal to 52.3%. The parameters of Cr2+:CdS and Cr2+:CdSe lasers are compared. A Cr2+:CdSe crystal generated 1.7 W of cw radiation at 2638 nm with the slope efficiency with respect to the absorbed power equal to 53.4%.

The influence of atomic iodine donors (CH3I and CF3I) on the output energy of a pulsed oxygen-iodine laser was investigated. Their influence on the time dependence of the luminescence intensity of I (2P1/2) iodine atoms formed by laser photolysis of an RI–O2–M mixture (R = CH3, CF3, M is the buffer gas) was also studied. An analysis of the experimental data and of the results of numerical modeling, demonstrated that when CF3I was used as the iodine donor, CF3O2 quenched strongly the O2(1Δ) excited oxygen. The proposed kinetic model yielded the rate constant k = (3–5) × 10−11 cm3/s for the reaction O2 (1Δ) + CF3O2 → O2 (3∑) + CF3O2.

Singlet delta oxygen O 2 (Z 1 ' g ) (SDO) production in a slab discharges ignited in oxygen gas mixtures was experimentally studied. An influence of gas mixture content and input electric power on SDO yield was analyzed. In self-sustained RF slab discharge SDO yield of 10±5% was measured by comparison luminescence intensity of SDO going from a chemical generator and SDO generated in electric discharge. SDO yield of 7.2% was measured by intracavity laser spectroscopy method. It was demonstrated that the choice of electrodes material is very important. Experiments on SDO production in slab non-self-sustained discharge with external ionization by repeating high-voltage pulses were carried out. SDO concentration was measured by the method of intracavity laser spectroscopy. The measured concentration of SDO was about 1.5 10 16 cm -3 , with SDO yield of ~10.6%. A development of electric discharge oxygen-iodine laser with SDO production in long electrodes slab discharge is discussed. Keywords: singlet delta oxygen, singlet oxygen yield, slab discharge, RF discharge, non-self-sustainted discharge, intracavity laser spectroscopy

Singlet delta oxygen O 2 (a 1 Δ g ) (SDO) production in a slab discharges ignited in oxygen gas mixtures was experimentally studied. An influence of gas mixture content and input electric power on SDO yield was analyzed. In self-sustained RF slab discharge SDO yield of 10±5% was measured by comparison luminescence intensity of SDO going from a chemical generator and SDO generated in electric discharge. SDO yield of 7.2% was measured by intracavity laser spectroscopy method. It was demonstrated that the choice of electrodes material is very important. Experiments on SDO production in slab non-self-sustained discharge with external ionization by repeating high-voltage pulses were carried out. SDO concentration was measured by the method of intracavity laser spectroscopy. The measured concentration of SDO was about 1.5 10 16 cm -3 , with SDO yield of ∼10.6%. A development of electric discharge oxygen-iodine laser with SDO production in long electrodes slab discharge is discussed.

Efficient lasing of Fe:ZnSe was demonstrated with a 2.94 pm Er:YAG pump laser. Output energy of 130 mJ, an absorbed energy slope efficiency of 44% and continuous tunability from 3.8 to 4.4 pm at 85 K were obtained. Laser efficiencies were determined for temperatures ranging from 85 to 253 K.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The dynamics of the intracavity absorption was studied in a cw Co:MgF2 laser. The linear growth of the intracavity absorption was observed for the generation time values form 0 to at least 4 ms which corresponds to a 1200-km effective absorption path length.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The feasibility of developing an HgBr laser utilizing the B2∑+1/2→X2∑+1/2 transition by optical pumping of HgBr(X) radicals using the third harmonic of a neodymium laser was studied. The radicals were formed by photolysis of a mixture of HgBr2 vapor with various buffer gases using the fourth harmonic of the neodymium laser. Under these conditions the luminescence was due to the B–X transition in the HgBr radical and its intensity was three orders of magnitude lower than that calculated from the absorbed third-harmonic energy, basing due to the B→X transition in the HgBr radical could not be achieved. When the mixture was exposed to the fourth-harmonic radiation, emission of the 73S1–63P2 (λ = 546 nm) mercury line was observed and the output pulse energy increased with increasing pump energy.

The luminescence spectra (600–700 nm) were determined for active media of a chemical oxygen–iodine laser with different iodine concentrations. The red radiation observed at low iodine concentrations was attributed to the ICl molecule.

An investigation was made of the influence of the addition of polyatomic gases on the energetics of an H2–F2 laser in the case of controlled initial initiation. The results obtained indicated the presence of two mechanisms for raising the output energy of an H2–F2 laser. The first mechanism is common to all gases and involves a change in the specific heat. The second mechanism is specific to particular gases and is associated with an increased rate of the establishment of a rotational equilibrium of the HF molecules. The extent to which polyatomic gases have an effect depends strongly on the initial experimental conditions.

A study was made of the dependence of the duration of emission from an atmospheric-pressure H2–F2 laser on the composition of the mixture and on the degree of initiation. The initiation source was a neodymium glass laser system with a harmonic generator emitting 10-nsec pulses of the third and fourth harmonics which reached energies of 5 and 2J, respectively. The duration of emission from the H2–F2 laser was 45 nsec when the initial concentration of the fluorine atoms was [F]o=3×1017cm−3 and the composition of the mixture was F2:O2:H2:He=300:30:100:320 Torr. The divergence of the radiation emitted by this chemical laser was 1.1 mrad when the specific output energy was 40J/liter; this divergence was only 1.6 times greater than the diffraction limit.

The results are presented of an experimental investigation of the energy characteristics of an H2–F2 laser with partial pressures of F2 and H2 of 3 Torr, as a function of the initial initiation α and of the pressure of the diluent gas (He or SF6). In an F2:H2:O2:He = 3:3:1.2:30 Torr gas mixture when α = 8%, a specific output energy per unit volume of ev = 4.4 J/liter was obtained for a specific output energy per unit mass of em = 330 J/g. The results obtained provided evidence of the advantage of using the chain excitation mechanism in cw HF lasers.

Stimulated emission from an oxygen–iodine laser with a photodissociation source of excited oxygen O2(1Δ), based on ultraviolet photolysis of ozone, was observed for the first time. The ozone photolysis products, particularly O(1D) atoms, had an unfavorable influence on the lasing parameters. A study was made of the possibility of using CO2, N2, and N2O gases as effective agents for quenching of O (1D). An output energy e = 0.8 mJ/cm3 and an efficiency of energy transfer from the O2(1Δ) molecules to iodine atoms amounting to η = 41% obtained for a mixture of the composition characterized by the ratio CF3I:O3:SF6:He:N2O = 0.055:0.45:11:21:6 Torr were close to the corresponding values reported for an oxygen–iodine laser with a chemical generator of O2(1Δ).

A comparison of the output parameters of an H2–F2 laser initiated alternately by photolysis and electron beam methods was used to find the energy eFe = 4.3±0.9 eV needed to form one fluorine atom by an electron beam.

Quasi-cw operation of an IF(B–X) laser was achieved as a result of filling of levels by VT relaxation. The duration of emission from the IF laser was governed by the duration of the pump pulses and it amounted to 25 μs. The output energy was 3 mJ and the quantum efficiency was 15% relative to the absorbed pump radiation. An estimate was obtained of the VT relaxation rate constant of the ground state of the IF(X) molecule interacting with helium: kVT ≈ 10− 13 cm3/s.