V. F. Losev

Multi-terawatt femtosecond laser system of visible range based on a photochemical XeF(C-A) amplifier

AbstractThis paper reports on the creation of a THL-100 multi-terawatt hybrid laser system based on a Start-480M titanium-sapphire starting complex and photochemical XeF(C-A) amplifier with a 25-cm aperture. The complex produces 50-fsradiation pulses of energy up to 5 mJ at a second harmonic wavelength of 475 nm. The active medium of the amplifieris created in a XeF 2 /N 2 mixture under vacuum-ultraviolet radiation of electron beam-excited xenon. The results of firstexperiments on femtosecond pulse amplification in the active medium of the XeF(C-A) amplifier are presented todemonstrate that a laser beam peak power of 14 TW has been attained.Keywords: Chirped pulses; Femtosecond pulses; Hybrid (solid/gas) laser system; Photochemical XeF(C-A) amplifier;Second harmonic INTRODUCTIONAt present, the development of ultra-high power laser sys-tems with a pulse duration of 10–100 fs is based mainly onnear-infrared solid-state titanium-sapphire or parametric am-plifiers and amplification of positively chirped pluses, i.e.,stretched in time (0.5–1 ns), by linear frequency modulation(Strickland & Mourou, 1985) with their subsequent com-pression to the initial duration. Stretching of a pulse is re-quired to decrease its power below a threshold at which thebeam is self-focused; in solid-state systems, pulses are nor-mally stretched about 10

Development of a hybrid (solid state/gas) femtosecond laser system of multiterawatt peak power

Terawatt hybrid laser (THL-100) system on the basis of Ti:sapphire starting complex and final amplifier with gaseous optically driven active media on XeF(C-A) molecules is presented. Laser system is built at Institute of High Current Electronics SB RAS, Tomsk, Russia. It consists of Ti:sapphire starting complex and photochemical XeF(C-A) amplifier. The active media of amplifier pumped by VUV radiation has 24 cm aperture and 110 cm length. The results of numerical modeling of the output parameters and first experimental results are presented in this paper.

Development of a 100-terawatt hybrid femtosecond laser system

Terawatt hybrid (solid state/gas) laser (THL-100) system on the basis of Ti:sapphire starting complex (50 fs, 5 mJ) and photochemical XeF(C-A) amplifier with the aperture of 24 cm is presented. Laser system is built at Institute of High Current Electronics SD RAS, Tomsk, Russia. The design and peculiarities of optical pumping of XeF(C-A) amplifier, methods of pump power measuring, gain distribution across the active volume are discussed. The results of numerical modeling of the output parameters simulation are presented and one compared with first experimental results.

LBO: optical properties and potential for THz application

High quality lithium borate (LBO) samples cut along (1 0 0), (0 1 0) and (0 0 1) axes were studied by terahertz time-domain spectroscopy (THz TDS) between 0.2–3 THz. It was found that in the direction of crystallographic axis X the optical absorption coefficient is the lowest amongst all known anisotropic nonlinear crystals, and that birefringence is as large as 0.42. Dispersion equations for the entire transparency range of LBO were developed for the first time. Phase matching for down-conversion into the THz range was found to be possible. Phase matching availability, low optical loss in the transparency band, and high optical damage threshold make LBO one of the most promising nonlinear materials for THz generation.

Interaction of high intensity optical pulses with modified nonlinear GaSe crystals

The modified Bridgman method with heat field rotation was used to grow ε-polytype single crystals of pure and 1, 2 and 10 mass % S-doped GaSe or solid solution crystals GaSe1-xSx, x = 0.002, 0.091, 0.412. The interaction of ultrashort laser pulses of ∼ 100 fs duration at 800 nm and 2 μm with the grown crystals was studied at room temperature. Up to 3.4-fold advantage of S-doped crystals in limit pump intensity (no decrease in the transmission) was found under 800 nm pump at S-content increase up to 10 mass %. The advantage became a half less at 2 μm pump due to a decrease of two-photon absorption in pure GaSe crystals. The spectral dependence of transient absorption is recorded with 37 fs resolution and interpreted. It was ascertained that first observable damage of high quality crystals is caused by dissociation of submicrometer thick surface layer to initial elements and do not influence the frequency conversion efficiency until alloying of dissociated Ga. Local microdefects, multiphoton absorption and transient transmission processes are identified as key factors responsible for damage threshold.

Electron-beam-pumped high-power wide-aperture exciplex lasers and laser systems

High-efficiency, high-power pulsedXeCl* andKrF* lasers pumped with an electron beam and laser systems based on these lasers have been developed. This paper describes the principles embodied in their development and design. The results of investigations on the formation of high-quality, high-power pulses are presented. Pulses with a radiation energy of up to 2000 and 100 J have been obtained at λ=308 and 249 nm, respectively, with a minimum 10 μrad divergence of the beam.

Xenon laser action in discharge and electron-beam excited Ar—Xe mixture

Abstract The results of experimental investigations of the atomic Xe lasing in the near IR under excitation by an electron-beam, an e-beam controlled discharge and a discharge with ultraviolet preionization are presented in this paper. It is shown that with the use of any of the above methods of pumping, the maximum efficiency and energy of the laser were attained in mixtures with Ar. An output energy of 7 J and a specific energy of 2.3 J/1 with ∼ 1% efficiency were obtained under the e-beam excitation.

Generating femtosecond pulses in the mid-IR and THz ranges in GaSe1 − xTex crystals

GaSe crystals with 0, 0.07, 0.38, 0.67, 2.07, 3, and 5 wt % Te are grown. GaSe:Te (≤2.07 wt %) crystals are suitable for nonlinear optics applications. The optimum doping level is 0.07 wt %. This minimizes optical losses and increases the damage threshold by ≥20%, hardness by 33%, and the efficiency of femtosecond Ti:Sa laser frequency conversion into the 8.8–24 μm and 0.2–3 THz ranges by ≥50%.

Development of hybrid (solid/gas state) ultra-high power femtosecond laser system on the basis of XeF(C-A) amplifier

A terawatt hybrid laser(THL-100) system on the basis of a starting complex and a final amplifier with gaseous optically driven active media on XeF(C-A) molecules is presented.The starting complex manufactured consists of a Ti: sapphire master oscillator pumped by femtosecond pulses from a continuous laser pumped by(Verdy-8) at a wavelength of 532 nm,a femtosecond pulse stretcher,regenerative and multipass amplifiers pumped by a pulsed laser at a wavelength of 532 nm,a diffraction grating compressor and a second harmonic generator(KDP).The complex has the following output parameters of the laser beam: pulse duration is 50 fs,the energy of radiation at the second harmonic(475 nm) is 5 mJ.The complex can operate in a single pulse mode and a frequency of 10 Hz. The XeF(C-A) amplifier consists of a two high-voltage pulsed generator(linear transformer),a vacuum diode with six cold explosive-emission cathodes,a electron beam injection system,a Xe filled gas chamber-converter and a laser cell.The high-voltage generator consists of 12 transformer stages,and each of them involves eight capacitors(one is C=40 nF) and spark gaps.The capacitors can be charged up to voltage of 100 kV.E-beam in vacuum diode has the parameters in total current of 300 kA,peak voltage of 550 kV,pulse duration of e-beam power about 150 ns(FWHM).The total energies of the six 100 cm ×12 cm e-beams which pass through the foil into the Xe converter are 6-7 kJ in the 150-160 ns pulse(FWHM).Pump energy cascade processes lead rapidly to the formation of Xe*2,which radiates a fraction of the deposited energy in the continuum at(172 ± 5) nm.This VUV radiation is transmitted through CaF2 windows into the laser cell containing the mixture of XeF2 vapour and N2 buffer gas.VUV radiation makes photolysis of XeF2 molecules form XeF* excimer molecules.The active medium of the amplifier pumped by VUV radiation has 24 cm aperture and 110 cm length.The results of numerical modeling of the output parameters and first experimental results are presented in this paper.According to the modeling of the XeF(C-A) amplifier parameters and the first measurement of gain,it is shown that the maxmum output energy is 2-3 J,which means that the peak power has been up to 40-60 TW in a 50 fs pulse.Furthermore,It is very important that this laser system can provide a high temporal contrast up to 109-1010.

High-power excimer laser systems

Two-high power excimer laser systems with square (25 × 25 cm) and circular (with a diameter of 40 cm) cross sections of the output laser beam are described. The first (second) system consists of four (five) excimer lasers. The experimental results on the generation of the high-quality high-power laser pulses are presented. Laser beams with a pulse duration of 1–250 ns, a divergence of 0.01 mrad, a spectral line width of 0.01 cm−1, and a pulse energy of up to 330 J are obtained.