Tasoltan T. Basiev

Spectroscopic and laser properties of Nd3+ doped fluoride crystals in 1.3-um region

For a number of neodymium doped fluoride crystals both with regular and disordered structure the Judd-Ofelt analysis of absorption spectra have been performed, and fluorescence and lasing spectra were studied in order to reveal the most promising materials for optical amplification in a 1.3 micrometers telecommunication window. The most suitable crystalline media investigated was found to be cubic disordered fluorides based on (50 - 70%) SrF2 - (50 - 30%) CaF2 solid solutions with Nd3+ optical centers having tetragonal local symmetry. These crystals have (1) low value of excited state absorption line strength, (2) high metastable level lifetime (1.2 - 1.3 ms), (3) high enough emission cross section for fluorescence (approximately 4 X 10-21 cm2), and (4) proper fluorescence peak at about 1310 nm wavelength and comparatively wide fluorescence band with about 20 nm FWHM.

New Visible SrF2:Pr3+ Ceramic Laser at 639 nm

For the first time to our knowledge SrF2:Pr3+ fluoride ceramics was developed and visible 639 nm wavelength oscillations were obtained in diode pumped CW mode with slope efficiency above 9%.

Spectroscopic and Oscillation Properties of Yb 3+ Ions in BaF 2 -SrF 2 -CaF 2 Crystals and Ceramics

Absorption and emission cross sections of Yb3+ions in SrF2crystal and CaF2-SrF2and BaF2-SrF2solid solutions were determined. Tuning in 1000-1080 nm region was observed. Physicochemical and oscillation properties of CaF2ceramic were investigated.

Tunability of Lasers Based on Yb 3+ -Doped Fluorides SrF 2 , SrF 2 -CaF 2 , SrF 2 -BaF 2 , and YLF

Ytterbium doped fluorides were investigated as gain medium in diode pumped laser, tunable using birefringent filter. Smooth, broad tunability was reached using new fluoride solid solutions Yb:SrF2-CaF2(1005 −1082 nm) and Yb:SrF2-BaF2(1004 1083 nm).

Accumulated photon echo in CaF2-YF3 : Nd3+ crystals

Abstract Accumulated photon echoes were used to measure 1–800 ps dephasing times ( T 2 ) for the 4 I 9/2 → 4 G 5/2 , 2 G 7/2 transition of Nd 3+ ions located in two different symmetry sites in highly disordered CaF 2 -YF 3 crystals. The temperature dependence of 1/(π T 2 ) from 9–100 K is described by a single phonon absorption process.

BaWO4 crystal for quasi-cw yellow Raman laser

The possibility to use BaWO4 solid state Raman laser for conversion of quasi-cw laser radiation has been demonstrated. The operation of yellow Raman laser with 1 kHz repetition rate and pulse width 10-600 ns under pumping with second harmonic of Nd3+:YLiF4 laser (527 nm) was investigated. The 1st Stokes (544 nm) and 2nd Stokes (583 nm) component radiation with promising characteristics was obtained at 1-10 W pump power.

ZnSe:Cr 2+ laser coherently pumped by Er:YAP 1.66 μm laser or Tm: YAP 1.97 μm laser

Tunable mid-infrared laser radiation sources are of interest for many applications in spectroscopy, ranging, remote-sensing, medical diagnosis and treatment and also for pumping nonlinear (OPO) and laser materials. The ZnSe:Cr2+ is a promising laser active material for lasing in the range of 2-3 μm. Up to now number of sources have been used for pumping ZnSe:Cr2+ active medium: Er-fibre laser, color-center laser, Co:MgF2 laser, Tm lasers, and Raman-shifted Nd:YAG laser [1-4]. In our study we have demonstrated, characterized and compared ZnSe:Cr2+ laser coherently pumped either by flashlamp-pumped Er:YAP (wavelength 1.66 μm) or diode pumped Tm:YAP (wavelength 1.97 μm) laser radiations. For the case of ZnSe:Cr2+ laser pumping by wavelength 1.66 μm, the Er:YAP laser was constructed. From the measured output radiation characteristics followed that the maximal ZnSe:Cr 2+ laser output pulse energy was 5.5 mJ (slope efficiency 23%), and the length of pulse 120-160 μs. With the help of dispersive prism inside the resonator, the generated laser radiation was tunable from 2100 nm to 2450 nm with only 2 times drop in laser efficiency. The temporal profile and spatial structure of the generated laser beam were measured. Consequently, the diode-pumped Tm:YAP laser was constructed for coherently pumped ZnSe:Cr2+ laser. LIMO laser diode (40 W) was used for longitudinal pumping of Tm:YAP laser. The output characteristics and tuning curves were measured for various ZnSe:Cr2+ laser resonator arrangements and also for various pumping radiation conditions in pulsed regime (pulse duration, repetition rate, duty cycle). The maximal obtained ZnSe:Cr2+ laser output pulse energy was 0.35 mJ for the Tm:YAP pump pulse energy 13.5 mJ (pulse radiation 5 ms, repetition rate 20 Hz). The generated laser radiation was tunable from 2100 nm to 2450 nm. The temporal profile and spatial structure of the generated laser beam were measured.

Nd:BaWO4 Raman Laser

Raman laser was constructed on the base of new Nd:BaWO4 material Q-switched by LiF:F2- crystal. Emission at 1169 nm was obtained in 1.3 ns long pulse with energy 0.8 mJ.

Stimulated Raman Scattering in the Mid IR Range 2.31-2.75-3.7 µm in a BaWO4 Crystal under 1.9 and 1.56 µm Pumping

The first Stokes component (2.31 µm) and four Stokes components up to 2.75 and 3.7-µm were obtained in a BaWO4 crystal under 1.9-µm and 1.56-µm pumping, respectively. SRS and laser breakdown thresholds were measured.

Nd:SrWO 4 Raman laser

Properties of the laser operation and simultaneously stimulated Raman scattering in the new SRS-active neodymium doped SrWO4 crystal coherently end-pumped by alexandrite 752 nm laser radiation were investigated. The maximum generated energy 90 mJ from the free-running Nd3+:SrWO4 laser at 1057 nm wavelength was obtained with the output coupler reflectivity 52%. The slope efficiency reached s = 0.52, the beam characteristic parameters M2 and divergence q were 2.5 ± 0.1, and 1.5 ± 0.1 mrad, respectively. Maximal output energy of 1.46 mJ for the fundamental wavelength was obtained for Q-switched Nd3+:SrWO4 oscillator with a double Fabry-Perrot as the output coupler (R = 48%), and with the 5% initial transmission of LiF:F2- saturable absorber. Up to 0.74 mJ energy was registered at the first Stokes frequency. The pulse duration was 5 ns and 2.4 ns for the fundamental and Stokes radiation, respectively. The energy of 1.25 mJ at 1170 nm was obtained for closed Raman resonator with special mirrors. For the case of mode-locking, two dye saturable absorbers (ML51 dye in dichlorethan and 3955 dye in ethanol) were used and SRS radiation in the form of pulse train was observed. The influence of the various Raman laser output couplers reflectivity as well as the initial transmissions of passive absorbers were investigated with the goal of the output energy maximization at the Stokes wavelength. In the output, the total measured energy was 1.8 mJ (for ML51 dye) and 2.4 mJ (for 3955 dye). The SRS output at 1170 nm was approximately 20% of total energy.