Barium Nitrate Crystal Research Articles

Development of Methods for Growing LiIO3 and Ba(NO3)2 Crystals as Materials for Laser Frequency Converters

New methods for growing LiIO3 and Ba(NO3)2 crystals have been developed. Barium nitrate crystals up to 12 × 12 × 100 mm3 in size and lithium iodate crystals up to 120 × 120 × 200 mm3 in size of necessary optical quality are obtained. The influence of рН on the morphology of Ba(NO3)2 growth faces is investigated. The data on the morphology of the {111} and {$$\bar {1}\bar {1}\bar {1}$$} faces of crystals grown at different solution acidities are obtained by atomic force scanning microscopy. The possibility of fabricating optical elements from LiIO3 crystals of ~100 × 100 × 100 mm3 in size is shown.

Raman Laser with a Singly Resonant Cavity: Theoretical Model and Experiment

A semiclassical theoretical model of a Raman laser possessing a cavity which is resonant at the Stokes wavelength and not resonant at the pump wavelength has been developed. The wave equations describing evolution of amplitudes of the pump and Stokes pulses in the Raman cavity have been derived. Results of the theoretical modeling have been analyzed for conditions of an experiment with the Raman laser on barium nitrate crystal under the nanosecond pulse pump. Numerically calculated energy characteristics of the Raman laser as well as space-time dynamics of the Stokes generation have been demonstrated to be in reasonable agreement with the experiment.

Influence studies of doping on FTIR Spectra and Thermogravimetric Analysis of Barium Nitrate Crystals

Pure and Magnesium Nitrate hexahydrate (MgN) doped Barium Nitrate (BaN) crystals were grown by slow evaporation technique. FTIR spectral studies have been carried to identify the presence various functional groups. An FTIR spectrum of grown crystals confirms the presence of ionic bonds in the structure of pure and doped BaN crystals. The influence of MgN doping on FTIR spectra was absorbing frequencies by pure and doped BaN crystals were studied. Thermogravimetric of pure and doped BaN crystals were analysed to characterise thermal stability. Thermal parameters are evaluated using thermogram. The results are presented and discussed in this paper.

Generation of sub-100-fs Stokes pulses upon SRS in a barium nitrate crystal

72-fs pulses are generated at the first Stokes component frequency upon stimulated Raman scattering in a barium nitrate crystal for the radiation of the Ti3+:Al2O3 laser with the pulse duration of 50 fs. The energy efficiency of conversion is 20%. The barium nitrate crystal was optically pumped by two consecutive orthogonally polarised chirped pulses with the following time compression of the Stokes radiation pulse.

(2+1)D surface solitons in virtue of the cooperation of nonlocal and local nonlinearities

We introduce a type of (2+1)D surface soliton in virtue of the cooperation of nonlocal and local nonlinearities. Furthermore, taking advantage of diffusion and drift nonlinearity this type of surface soliton is demonstrated theoretically and experimentally in a storintium barium nitrate crystal. The dynamics behavior of the excitation and propagation of this type of surface soliton are studied using the beam-propagation method and the nonlinear equation of light rays.

Spectral shift of Raman generation band in a Bessel pump beam

A spectral shift in the first Stokes generation band has been observed at stimulated Raman scattering in a Bessel light beam. Under nanosecond pulse excitation in barium nitrate crystal, the Stokes emission propagating along the Bessel beam axis has been found to be frequency shifted toward the blue side by 3.7 GHz with respect to the Stokes emission propagating along the surface of a cone. Numerical data have shown that the observed frequency shift is directly related to the contribution of the real part of the Raman susceptibility to the refractive index. This contribution causes an increase in the Stokes gain out of exact Raman resonance owing to induced focusing, which inhibits diffraction spread of generated light and thus provides its better spatial overlap with the pump beam.

Efficient Raman amplification of low divergent radiation in barium nitrate crystal

One stage first Stokes amplification by a factor of 1600 was demonstrated in a barium nitrate Raman amplifier. The amplified pulse energy was up to 63 mJ at pump energy of 208 mJ. M2 factor of Stokes signal radiation was 1.5 while for amplified radiation 2.2.

Low-threshold lasing in stimulated Raman lasers with nanosecond pumping

We have studied the conditions resulting in maximum lowering of the excitation threshold for pulsed stimulated Raman (SRS) lasers. It has been shown theoretically that in order to achieve the lowest possible values of laser radiation pulse energy needed to excite lasing in SRS lasers, we need high reflection of the cavity mirrors and low losses at the wavelength of the 1st Stokes component, high reflection of the output mirror at the wavelength of the pump radiation, and also matching of the confocal parameters for the exciting laser radiation and the cavity with each other and with the length of the Raman-active medium. The experimentally achieved excitation threshold for an SRS laser based on a barium nitrate crystal was 6 µJ, which quantitatively corresponds well to the calculation results. Lasing of up to five Stokes components simultaneously occurred. The efficiency for conversion of the laser radiation to one component was as high as 39%.

Numerical optimization of the extracavity Raman laser with barium nitrate crystal

The radiation transfer equations of the extracavity Raman laser including up to the third Stokes beams and backward Raman scattering terms were deduced in detail from the wave equation and material equations of stimulated Raman scattering. The radiation transfer equations were solved numerically to optimize the performance of the extracavity Raman lasers with barium nitrate crystal as the nonlinear medium. The optimum reflectivity of the output coupler at the first Stokes was figured out numerically to achieve the maximum conversion efficiency of the first Stokes, and found to be closely related to the pump pulse duration, peak intensity of the pump pulse, and Raman crystal length. With the resonator mirrors highly reflective at the first Stokes, the highest conversion efficiency of the second Stokes was obtained when the input mirror was highly reflective at second Stokes, whereas the output coupler was highly transmissive at the second Stokes. It was found that too high intracavity intensity of the second Stokes would impede the efficient energy extraction from the pump pulse to the first Stokes, and consequently, limit the conversion efficiency of the second Stokes.

Beam quality improvement at Raman conversion of multimode conical beam

The spatial structure of Raman-converted radiation was investigated numerically and experimentally for the case when the pump is a conical beam produced by an axicone from multimode laser radiation. Both conical and axial Stokes beam generation was found to be possible. The improvement of the laser beam quality was demonstrated numerically and supported by experiment on Raman conversion in barium nitrate crystal. The laser beam with the beam quality factor M2=11 was converted into the axial Stokes beam with M2=3.5 at the conversion efficiency of 20%. A two-times increase in the Stokes beam brightness was obtained.

Stimulated Raman conversion of radiation from a YAG:Nd laser with wavelengths of 1.319, 1.338, and 1.357 µm in a barium nitrate crystal

We have studied stimulated Raman (SRS) conversion to the first Stokes component of multimode (M2 = 8) radiation from a YAG:Nd laser with lasing wavelengths of 1.319 µm, 1.338 µm, and 1.357 µm in a barium nitrate crystal. We have obtained pulses of converted radiation with energies up to 120 mJ. We have achieved conversion efficiencies greater than 40% for each of the three Raman laser wavelengths of 1.530 µm, 1.556 µm, and 1.582 µm with divergence of the beams of converted radiation close to the diffraction-limited value (M2 < 1.5).

RAMAN GAIN COEFFICIENT OF BARIUM NITRATE MEASURED FOR THE SPECTRAL REGION OF TI:SAPPHIRE LASER

We report the measurements of the Raman gain coefficient for a barium nitrate crystal in the spectral region of a Ti:Sapphire laser using Raman amplification. The experimentally-obtained data are well described by the known empirical formula.

Multimode pumped continuous-wave solid-state Raman laser

We demonstrate the continuous-wave operation of a solid-state Raman laser containing a barium nitrate crystal as the Raman medium. The Raman laser, which has a singly resonant cavity, is pumped by multimode radiation. The Raman oscillation threshold is reached at approximately 2 W of pump power. As much as 500 kW/cm2 of Stokes power density at 60-kW/cm2 pump power density is obtained in the cavity.

Numerical Simulation of SRS of Cylindrical Wave Beams

A method for numerical simulation of stimulated Raman scattering of cylindrical wave beams in a nonlinear medium has been developed. The features of the spatial structure formation of interacting wave fields in the regime of conservation of azimuthal angular distributions of amplitudes have been investigated. The radial intensity profiles of diffracting light beams in the near-field zone and their angular spectra in the far-field zone corresponding to different stages of energy exchange in the process of amplification from the noise in the barium nitrate crystal have been calculated. It has been shown that in the field of Bessel beams waveguide structures of the soliton type with a peak intensity of the self-channeling Stokes component significantly exceeding the initial pumping intensity are formed. A comparison of the conversion efficiencies under pumping by Gaussian and Bessel light beams has been made.

Effect of centrifugation on the crystal structure of barium nitrate

The structure of barium nitrate crystals grown from supersaturated aqueous solutions under normal conditions and during centrifugation at 11.8×103g is studied for the first time by a high-precision powder neutron diffraction method. It is established for the first time that centrifuging leads to displacement of the nitrate oxygen atoms in the xy plane (resulting in rotation of the NO3 trigonal prism about the third-order axis) and to variation of the bond lengths and angles in the coordination polyhedron of Ba atoms. The latter changes result in the appearance of a torsional mode in the phonon spectrum of barium nitrate and in increasing stiffness of the crystal lattice, as evidenced by a significant increase in microhardness of the samples grown in the centrifuge.

Stimulated Raman scattering in alkaline-earth tungstate crystals

Results on spontaneous Raman spectroscopy of alkaline-earth tungstate crystals are presented. The frequency of the modes active in stimulated Raman scattering (SRS) modes was found to increase and their width to decrease with increasing cation radius and mass in the series of alkaline-earth (Ca, Sr, Ba) tungstates. High peak values of the Raman scattering cross section for barium and strontium tungstate crystals — new media offering promise for SRS — were predicted and observed in the experiments. Laser experiments on the SRS threshold showed that the SRS gain for the barium tungstate crystal was close to the record value observed for the barium nitrate crystal, which is extensively used in SRS.

Comparative spontaneous Raman spectroscopy of crystals for Raman lasers

A comparison of the spectroscopic parameters of Raman-active vibronic modes in various crystalline materials with a view to the use of these crystals for stimulated Raman scattering (SRS) is presented. It includes data on the Raman frequency shift, linewidth, integral, and peak Raman scattering cross sections. For steady-state SRS the highest Raman gain coefficient has been proved to be in barium nitrate and sodium nitrate crystals; for transient SRS it is expected to be in lithium niobate and tungstate crystals. Barium tungstate and strontium tungstate are proposed as new highly efficient Raman materials for both SRS cases.

Physical, chemical and optical properties of barium nitrate Raman crystal

The physical, chemical and optical properties of barium nitrate crystal are considered from the point of its application for development of solid state Raman lasers and shifters. The described growth procedure has shown the possibility to fabricate laser elements with high optical homogeneity. Using Raman spectroscopic investigation of vibronic modes in barium nitrate crystal the linewidth broadening and frequency shift were measured. This proved that internal Raman modes in barium nitrate crystal have weak couplings with lattice phonons that results in high gain of Stimulated Raman Scattering (SRS).

Raman spectroscopy of crystals for stimulated Raman scattering

Raman frequency shift, line width, integral and peak Raman scattering cross sections were measured in various crystals using spontaneous Raman spectroscopy. The highest Raman gain coefficient in steady state Stimulated Raman Scattering (SRS) regime was proved to be in barium nitrate crystal; for transient SRS it is expected to be in lithium niobate and tungstate crystals. Barium molybdate crystal is proposed as a new highly efficient Raman material. OCIS: 300.6450; 290.5910; 190.2640

Stimulated Raman scattering of laser radiation in Raman crystals

Experimental study of stimulated Raman scattering (SRS) in barium nitrate and potassium gadolinium tungstate crystals are presented. Main features of crystalline single and multipass Raman shifters, Raman lasers with external and intracavity pumping are investigated and compared. Optimization of the optical schemes resulted in development of compact solid state Raman lasers for new important near infrared and eye safe spectral region of 1.2–1.5 μm.