S. V. Alekseev

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.

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.

Amplification of sub-nanosecond pulse in THL-100 laser system

The results of the formation and amplification of positive chirped 0.1 ns laser pulse at a central wavelength of 470 nm in the laser system THL-100 are presented. It is shown that a front-end allows forming a radiation pulse with a Gaussian intensity profile and the energy up to 7 mJ. At amplification in XeF(C-A) amplifier of the pulse with 2-5 mJ energy a saturated mode is realized and 3.2 J output laser beam energy is reached.

Formation of defects in lithium fluoride ceramics upon irradiation with femtosecond laser pulses

The interaction between femtosecond laser radiation in the filamentation mode and lithium fluoride optical ceramics is investigated experimentally. It is shown that irradiating optical ceramics based on lithium fluoride with femtosecond laser pulses in the near infrared spectral region effectively produces luminescence centers characteristic of radiation-colored single crystals.

Development of 100 terawatt hybrid laser system on base of photochemically driven XeF(C-A) amplifier

Development of terawatt hybrid (solid state/gas) laser (THL-100) system on the basis of Ti:sapphire starting complex 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 results of numerical modeling of the output parameters are discussed and first experimental results are presented. Simulation is shown that active medium of XeF(C-A) amplifier has gain in range of (1.8-4.5)×10−3cm−1 and it allows to extract by femtosecond pulse up to 3 J. This promises 60 TW output power to be produced in 50 fs pulse. In the first experiments when 2 mJ and 1 ps pulse was injected in XeF(C-A) amplifier the ∼1 J output energy and ∼10 TW power of was obtained.

Conditions of the generation of subnanosecond pulses in a THL-100 laser system

The results from the generation and amplification of positively chirped pulses of 0.05 ns duration at a central wavelength of 475 nm in a THL-100 laser system are presented. It is found that the initial complex allows the generation of such radiation pulses with Gaussian intensity profiles and energies of up to 7 mJ. When such pulses with energies of 2–4 mJ are amplified in an XeF(C-A) amplifier, it is possible to achieve a saturation mode and obtain at the output laser beams with energies of up to 3.2 J. The possibility of compressing subnanosecond pulses at a wavelength of 475 nm in a compressor based on diffraction gratings is demonstrated.

High power laser system of a visible range with output XeF(C-A) amplifire

THL-100 hybrid femtosecond laser system operating in the visible spectral range and the experimental results obtained by now are presented.

Broadening of the Spectra of Femtosecond Laser Pulses upon Passing through Optical Materials

Results from studying the conditions under which spectra generated by a 50 fs pulse from a Ti:Sa setup broaden at a wavelength of 475 nm are described, along with how to compensate for the accompanying positive dispersion. It is shown that the width of the spectra grows from 5 to 15 nm when the thickness of K8 glass is optimal. Pulse recompression with a spectral width of a 12.2 nm is achieved, along with a pulse duration of 22.6 fs.