A A Sirotkin

New lasers based on c-cut vanadat crystals

Spectroscopic and lasing properties of c-cut Nd-doped Nd:Gd0.7Y0.3VO4, Nd:YVO4, and Nd:GdVO4 crystals were investigated. Spectral tuning from 1062 to 1067 nm was demonstrated. CW, Q-switching and mode-locking regimes for two-color laser operations were realized. A novel THz source based on Q-switch two-color diode-pumped solid state c-cut Nd:GdVO4 laser with Filter Lio as selective element and the GaSe nonlinear optical crystals as convertor was demonstrated. Terahertz radiation with wavelength 436 mm (0.56 THz) was detected. One picosecond laser pulses in mode-locking diode pumped c-cut vanadat lasers with a Kerr-lens and PbS-doped glasses as saturable absorbers are observed.

Mid-IR (4–5 µm) femtosecond multipass amplification of optical parametric seed pulse up to gigawatt level in Fe2+:ZnSe with optical pumping by a solid-state 3 µm laser

We demonstrate a first-of-its-kind efficient amplification of a broadband tunable (from 3.8 to 4.8 µm) mid-IR femtosecond seed pulse generated from a AgGaS2-based optical parametric amplifier pumped by a Cr:forsterite laser in a multi-pass Fe2+:ZnSe amplifier optically pumped by a solid-state nanosecond Cr:Yb:Ho:YSGG laser. A total gain of 2000 for an input seed energy of 40 nJ has been obtained. The magnitude of the output energy reaches 80 µJ at a pulse duration of 200 fs.

Diode pumped Nd:YAG laser with active Q-switching and mode locking for hole drilling

A diode-pumped Nd:YAG laser operating with active-passive Q-switch mode locking, has been developed. The acousto-optic repetition train was one kilohertz with generated pulse train widths 65 ns, single pulse widths 200 ps and an average power of 6.5 W. Improvement of efficiency of small diameter deep holes laser drilling in different materials was studied.

The investigation of the laser properties of a new class of the mixed YxSc1 − xVO4:Nd3+ crystals

The investigation of structural perfection and laser properties of a new class of mixed vanadates YxSc1 − xVO4:Nd3+ was carried out in this work. The research of the structural perfection of the crystals was carried out by applying the X-ray diffractometer. It was shown that the YxSc1 − xVO4:Nd3+ crystals have a good structural perfection. The lasing experiment shows that the maximal CW output power of 2 W was achieved upon 5.8 W pumping. The maximal slope efficiency of 41.5% was obtained along the [100] crystallographic direction for the π-polarization.

Mid-IR (4–5 μm) hybrid sub-GW Fe 2+ :ZnSe femtosecond laser system

We demonstrate an efficient amplification of the broadband tunable (from 3.8 μm up to 4.8 μm) mid-IR femtosecond (∼200 fs) seed pulse in optically pumped Fe2+:ZnSe amplifier [1]. The experimental setup is sketched in Fig. 1a. Seed radiation was generated in two-stage AGS-based optical parametric amplifier pumped by Cr:forsterite laser [2]. Mid-IR output radiation with energy up to 1 μJ was then directed into a multipass amplifier. Iron-doped ZnSe crystal was pumped by Q-switched Cr:Yb:Ho:YSGG laser with 40 ns pulse duration, total energy of 20 mJ, operating at 2.85 μm wavelength [3]. In order to prevent carbon dioxide absorption, the last OPA stage and multi-pass amplifier was placed in the chamber, where atmospheric air was substituted by noble gas. Prior to the main experiments, gain evolution measurements were carried out. They have shown that the lifetime of population inversion of Fe2+:ZnSe strongly depends on the temperature. It increases from 350 ns (at room temperature) up to 1 μs (at 7 degrees Celsius) paving the way for multi-pass amplification. As a result, femtosecond seed radiation with energy 0.7 μJ centered at 4.3 μm was amplified in six-pass Fe2+:ZnSe amplifier up to the energy 70 μJ (Fig. 1b), which corresponds to 0.5 GW peak power. Decreasing of the input energy down to 40 nJ did not prevent to decrease in output energy. Therefore the total gain was about 2000. Inset in fig. 1 (b) presents far-field beam profile of amplified pulses. Substitution of air by argon removes spectral distortions in the laser pulse caused by the absorption by atmospheric CO2 molecules. It does not radically improve the amplification process in Fe2+:ZnSe but stabilizes the operating regime (Fig. 1c).

Gigawatt mid-IR (4-5 μm) femtosecond hybrid Fe2+:ZnSe laser system

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.

Control of spectral parameters in vanadate lasers

This paper presents laser sources based on a novel methods control of spectral parameters in diode-pumped vanadate lasers. The operation of diode-pumped passively Q-switched variable-cut (8=var, φ=0) Nd:YVO4, Nd:GdVO4 lasers with Cr4+:YAG saturable absorber was experimentally investigated and their relative advantages and drawbacks were compared. The best passively Q-switched performance obtained in the experiments is from the variable-cut (θ=25°, φ=0) laser, which gives the narrowest pulse of 2.5 ns with the highest peak power of 10.3 kW.

Vanadate lasers with {sigma}-polarised radiation

Luminescent and lasing properties at the {sup 4}F{sub 3/2} - {sup 4}I{sub 11/2} transition of {alpha}-cut Nd:YVO{sub 4}, Nd:GdVO{sub 4}, Nd:Gd{sub 1-x}Y{sub x}VO{sub 4} and Nd:Sc{sub 1-x}Y{sub x}VO{sub 4} vanadate crystals are experimentally studied for {pi}- and {sigma}-polarisations. Polarisation dependences of the lasing characteristics of passively Q-switched Nd:YVO{sub 4}, Nd:Gd{sub 1-x}Y{sub x}VO{sub 4} and Nd:Sc{sub 1-x}Y{sub x}VO{sub 4} lasers with Cr{sup 4+}:YAG and V{sup 3+}:YAG Q-switches are investigated. It is shown that the laser wavelengths are different for {pi}- and {sigma}-polarizations. The best characteristics are achieved for the Nd:YVO{sub 4} laser with a Cr{sup 4+}:YAG passive saturable absorber for {sigma}-polarisation (minimum pulse duration shorter than 3 ns, maximum peak power up to 10 kW, maximum peak energy {approx}35 {mu}J at a slope efficiency up to 32%). (lasers)

A 913-nm diode-pumped quasi-three-level Nd{sup 3+}:Gd{sub 0.7}Y{sub 0.3}VO{sub 4} laser

Lasing parameters of a mixed Nd{sup 3+}:Gd{sub 0.7}Y{sub 0.3}VO{sub 4} vanadate crystal emitting at the 913-nm {sup 4}F{sub 3/2}-{sup 4}I{sub 9/2} laser transition are studied. The output power of up to 600 mW was obtained upon longitudinal diode pumping for the absolute and slope laser efficiencies of {approx}13% and {approx}17%, respectively. (lasers)

Active and passive mode locking in a diode-pumped Nd:Gd{sub 0.7}Y{sub 0.3}VO{sub 4} laser

Diode-pumped lasers based on mixed Nd:Gd{sub 0.7}Y{sub 0.3}VO{sub 4} vanadate crystals are studied. Continuous-wave lasing with the slope efficiency of 71% and the average output power up to 8.2 W is obtained. Active mode locking with an acousto-optic modulator, passive mode locking by the Kerr nonlinearity, and hybrid mode locking are investigated. Picosecond laser pulses of duration 1.7 ps are obtained at an average output power of 340 mW and a pulse repetition rate of 140 MHz. (lasers)