Nonlinear Laser Crystal Research Articles

Pure and Yb-Doped LaxYySc4-x-y(BO3)4 Crystals: A Review of Recent Advances

This paper reviews the progress in developing the LaxYySc4-x-y(BO3)4-LYSB and Yb-doped LaxYySc4-x-y(BO3)4-LYSB:Yb huntite-type crystals grown by the Czochralski method as new candidates for the next generation of nonlinear optical (NLO) and/or laser crystals. Considering the incongruent melting of these crystals, the initial compositions of the melt and the pulling and rotation rates were optimized. Additionally, a special thermal setup was engineered to grow LYSB-type crystals by the Czochralski crystal growth method. The chemical compositions of the LYSB and LYSB:Yb grown crystals were found to be La0.78Y0.32Sc2.90(BO3)4 and La0.78Y0.32Yb0.04Sc2.86(BO3)4, respectively. Therefore, for the LYSB:Yb crystal, the doping concentration of Yb3+ ions was considered to be 4 at.% with respect to the nonstoichiometric (La1-xYx)1.25Sc2.75(BO3)4 undoped compounds, i.e., LYSB:Yb (4 at.%). In terms of NLO properties, the obtained results demonstrate that LYSB and LYSB:Yb (4 at.%) crystals possess remarkable properties specific to huntite-type crystals. The main advantage of these crystals consists in the fact that they may be obtained with large dimensions and excellent optical quality by the Czochralski method, which recommends them as a new class of highly efficient crystals for different NLO applications, including second harmonic generation (SHG) of high-power or high-energy laser beams. The laser performances of the LYSB:Yb (4 at.%) crystal prove its favorable intrinsic properties to generate laser emissions in the 1 µm range with high efficiency. The efficient laser emission at ~1028 nm together with good NLO characteristics to convert its own emission into emission at ~514 nm via SHG make the LYSB:Yb (4 at.%) crystal a very promising active medium to be used in self-frequency doubling configuration.

Pr:LGSB as a new nonlinear optical crystal: Czochralski growth and optical characterization

Herein, we report on the Czochralski growth and optical characterization of Pr:LGSB as a new nonlinear optical (NLO) and laser crystal. Single crystals of Pr:LGSB were grown by the Czochralski method, for the first time to the best of our knowledge, from the starting melt compositions La 0.656 Pr 0.022 Gd 0.572 Sc 2.75 (BO 3 ) 4 and La 0.651 Pr 0.027 Gd 0.572 Sc 2.75 (BO 3 ) 4 . The crystal growth parameters were optimized and two Pr:LGSB crystals with good optical quality were obtained. The chemical compositions of the grown crystals were determined to be La 0.750 Pr 0.020 Gd 0.450 Sc 2.780 (BO 3 ) 4 and La 0.743 Pr 0.025 Gd 0.452 Sc 2.780 (BO 3 ) 4 corresponding to a Pr 3+ ions concentration in the crystals of 2.0 at% and 2.5 at%, respectively. The spectroscopic properties were investigated and the obtained results show that the 2.5 at% Pr:LGSB is a promising laser crystal emitting in the orange spectral range at ~ 603 nm. The refractive indices were measured and the phase-matching curves for type I and type II SHG were determined. The walk-off angle, the external angular acceptance, and the nonlinear coefficient d 11 for type I SHG of 603 nm fundamental wavelength were also evaluated. This work shows that the 2.5 at% Pr:LGSB crystal could be a new promising candidate for obtaining laser sources in the UV range (~ 301.5 nm) in SFD configuration. • Pr:LGSB crystal were grown by the Czochralski method for the first time. • Spectroscopic and NLO properties of the 2.5 at% Pr:LGSB crystal are presented. • 2.5 at% Pr:LGSB has promising properties for laser emission in the orange domain. • Phase-matching curves for type I and type II SHG are determined. • Preliminary prospects for SFD in the UV domain were analyzed.

Modeling and Implementing Nonlinear Equations in Solid-State Lasers for Studying their Performance

In this paper, the effect of radius variation of beam light on output efficacy of SFD Yttrium aluminium borate laser doped with Neodymium ion, which is simultaneously a non-linear and active laser crystal, is investigated in a double-pass cavity. This is done with a concave lens that concentrates (Reduction of optical radius within nonlinear material) as much optical laser as possible, resulting in increasing the laser efficiency, second harmonic and the population inversion difference. In this study, we first developed five discrete differential equations describing the interactions of 807 nm pump beam, 1060nm laser beam and 530nm second harmonic beam. Output efficiencies of laser and second harmonic beams at pumping power of Pp =20W and beam radius of 5μm have been presented. Meanwhile, in this paper, the first experiment for creating second harmonic in solid state lasers was fully described with a figure and its procedure was investigated and then the equations (second harmonic and laser and population inversion) were studied. Radius variation of beam light aims at increasing laser output efficacy and improving second harmonic and population inversion. The analytic methods which have been solved the discrete differential equations via Matlab.

Frequency domain optical parametric amplification.

Today’s ultrafast lasers operate at the physical limits of optical materials to reach extreme performances. Amplification of single-cycle laser pulses with their corresponding octave-spanning spectra still remains a formidable challenge since the universal dilemma of gain narrowing sets limits for both real level pumped amplifiers as well as parametric amplifiers. We demonstrate that employing parametric amplification in the frequency domain rather than in time domain opens up new design opportunities for ultrafast laser science, with the potential to generate single-cycle multi-terawatt pulses. Fundamental restrictions arising from phase mismatch and damage threshold of nonlinear laser crystals are not only circumvented but also exploited to produce a synergy between increased seed spectrum and increased pump energy. This concept was successfully demonstrated by generating carrier envelope phase stable, 1.43 mJ two-cycle pulses at 1.8 μm wavelength.

Energy transfer properties of Nd3+→Yb3+ in Nd:Yb:LiNbO3 crystals

Abstract Nd:Yb:LiNbO 3 nonlinear laser crystal is a candidate for NIR laser around 1000 nm and self-frequency-doubling laser around 500 nm, with mature pump technique using ~808-nm diode laser, via Nd 3+ absorption and efficient Nd 3+ →Yb 3+ energy transfer. High-quality Nd:Yb:LiNbO 3 crystals were grown by Czochralski method, and the main spectroscopic properties of Nd 3+ →Yb 3+ (Nd 3+ : 4 F 3/2 +Yb 3+ : 2 F 7/2 →Nd 3+ : 4 I 9/2 +Yb 3+ : 2 F 5/2 ) energy transfer in LiNbO 3 crystals were studied systemically based on emission spectra and luminescence decay curves. Energy transfer efficiency as high as 86% was obtained in a Nd 3+ (0.8 mol%) and Yb 3+ (2.0 mol%) codoped sample, so Nd:Yb:LiNbO 3 laser with a higher efficiency than that of Nd:LiNbO 3 laser might be achieved under identical pump conditions.

Nonlinear plasmonics at planar metal surfaces

We investigate the nonlinear optical response of a noble metal surface. We derive the components of the third-order nonlinear susceptibility and determine an absolute value of χ((3))≈0.2 nm(2) V(-2), a value that is more than two orders of magnitude larger than the values found for typical nonlinear laser crystals. Using nonlinear four-wave mixing (4WM) with incident laser pulses of frequencies ω(1) and ω(2), we generate fields oscillating at the nonlinear frequency ω(4WM)=2ω(1)-ω(2). We identify and discuss three distinct regimes: (i) a regime where the 4WM field is propagating, (ii) a regime where it is evanescent, and (iii) a regime where the nonlinear response couples to surface plasmon polaritons.

High-contrast step-index waveguides in borate nonlinear laser crystals by 3D laser writing

We report the ultrafast fabrication of high-contrast step-index channel waveguides in Nd(3+):YCa(4)O(BO(3))(3) borate laser crystals by means of 3D direct laser writing. Guiding up to 3.4 μm wavelength is demonstrated for the first time in a laser written crystalline waveguide. Modeling the measured fundamental modes at the wavelengths of 1.9 µm and 3.4 µm allowed us to estimate the high laser-induced refractive index increments (index contrasts) to be 0.010 (0.59%), and 0.005 (0.29%), respectively. Confocal µ-Raman spectral imaging of the waveguides cross-sections confirmed that the cores have very well defined step profiles, and that the increase in the refractive index can be linked to the localized creation of permanent intrinsic defects. These results indicate that this crystalline waveguides are a potential candidate for the development of 3D active waveguide circuits, due to the laser and electro-optic properties of rare earth doped borate crystals.

Self-frequency-doubling of ultrafast laser inscribed neodymium doped yttrium aluminum borate waveguides

Buried channel optical waveguides, supporting orthogonal polarizations, have been fabricated in a neodymium doped yttrium aluminum borate nonlinear laser crystal by ultrafast laser inscription following the so-called “double line” approach. Confocal fluorescence and second harmonic imaging experiments have revealed that the original fluorescence and nonlinear properties have been not deteriorated by the waveguide inscription procedure. Preliminary laser experiments have shown the ability of the fabricated structures for green laser light generation under 808 nm optical pumping by self-frequency-doubling of the 1.06 μm laser line of neodymium ions.

Nonequivalent Yb3+ centres in Y1-xYbxAl3(BO3)4 laser crystals

The absorption spectra of nonlinear laser crystals Y1-xYbxAl3(BO3)4 grown from bismuth—lithium—molybdate and potassium—molybdate solution—melts are comparatively studied by high-resolution Fourier spectroscopy. The differences observed in the fine structure of the absorption spectra are correlated with the variations in the solution—melt composition and in the concentrations of bismuth and molybdenum impurities in the crystals. It is shown that the concentration of the molybdenum impurity (the main factor hindering lasing in the UV spectral region) in the single crystals grown from the bismuth—lithium—molybdate solutions is more than an order of magnitude smaller than in the crystals grown using the potassium—molybdate solution—melt. The described method can be used for express analysis of the quality of UV laser crystals and for improving the solution—melt technologies of growth of laser crystals and crystals used for generation of the fourth harmonic of Nd:YAG laser radiation.

Cover Picture: Efficient Two‐Photon Excited Amplified Spontaneous Emission from Organic Single Crystals (ChemPhysChem 9/2010)

Compared to currently widely used excimer and dye lasers, solid-state lasers offer obvious technical advantages. Two categories of solid-state laser technologies, namely sum-frequency of second harmonic generation (SHG) in nonlinear laser crystals and two-photon pumped (TPP) upconversion lasing of organic molecules are being adopted for wavelength shortening, of which the latter is more important, because phase matching requirements are eliminated. So far, TPP lasing has been realized for many applications, all based on molecules distribution into a polymer matrix. On p. 1871, Q. Yu, H. Sun et al. report Tpp upconversion cavityless lasing from an organic single crystal. The use of high quality crystals as the laser medium, significantly increasing the gain and the lasing efficiency and surmounting the shortcomings of polymer systems such as poor conduction, which results in a low damage threshold and short lasing lifetime, may pave the way to practical use for TPP solid-state laser sources.

New nonlinear laser effects in α-quartz: generation of a two-octave Stokes and anti-Stokes comb and cascaded lasing in the spectral range of the second and third harmonics

Crystals that are simultaneously χ(2)- and χ(3)-active offer a wide range of possibilities for the generation of new coherent wavelengths of light. Frequency conversion processes such as stimulated Raman scattering, second and third harmonic generation, or parametric sum and difference frequency mixing can be combined effectively in the same noncentrosymmetric crystal in cascaded χ(3) ↔ χ(2) lasing processes. We present several new manifestations of these effects under picosecond laser excitation in α-quartz (SiO2), the oldest nonlinear-laser crystal. Among them are 45 Stokes and anti-Stokes wavelength comb generation of more than two octaves (from 0.3692 μm to 1.5142 μm) and self-conversion of Raman-generation frequencies into the wavelength region of the second and third harmonics of one-micron pumping via many-step cascaded χ(3) ↔ χ(2) processes.

New nonlinear optical and laser crystals of borate family

(Er,Yb):YAl3(BO3)4 single crystals have been obtained using K2Mo3O10 based flux by dipping seeded solution growth at a cooling rate of 0.2–5 °C/day at temperatures from 1060 °C to 1000 °C. The Er and Yb segregation coefficients vary from 0.80 to 1.02. A valuable technique for characterizing the non-linear performance of the crystal to identify the presence of twins in borate materials has been developed. Over 1.1 W of green emission was obtained from a diode-pumped Yb:YAB laser. Spectroscopic properties of Er,Yb:YAB crystals have been investigated leading to the demonstration of efficient continuous-wave (CW) and Q-switched diode-pumped (Er,Yb):YAB laser operation.

Diode pumped passive Q switching of Yb3+-doped GdAl3(BO3)4 nonlinear laser crystal

The authors report the passive Q switching of a diode pumped Yb:GdAl3(BO3)4 (Yb:GAB) laser. The slopes of the average output power are 25% and 39.5% under different experimental conditions. The repetition rates occur in the 1–4.5kHz range and pulse energies of 125 and 165μJ with about 30ns duration are obtained. An experimental comparison with passively Q-switched Nd:GAB laser is provided. A theoretical analysis is performed. It is in reasonable agreement with the experimental data and it is shown to be a useful tool for predicting the optimization of the cavity parameters.

Temperature dependence of Nd3+↔Yb3+ energy transfer in the YAl3(BO3)4 nonlinear laser crystal

The temperature dependence of the Nd3+→Yb3+ energy-transfer rate in the YAl3(BO3)4 nonlinear laser crystal has been investigated from the analysis of fluorescence decay curves recorded in the 10–600 K range. Three different regimes, independent on the dopant concentration, have been observed in the thermal behavior of the Nd3+→Yb3+ energy-transfer rate. By comparing experimental results with theoretical predictions based on the Dexter model [J. Chem. Phys. 21, 836 (1953)], the origin of these different regimes has been explained. In addition, the influence of temperature and of both Nd3+ and Yb3+ concentrations on the Nd3+←Yb3+ energy back-transfer rate has been also investigated, concluding that it is a migration-assisted energy-transfer process. Finally, the populations of both Nd3+ and Yb3+ metastable states achieved after continuous-wave Nd3+ excitation have been calculated and measured and results have been explained in terms of the thermal behavior of both forward- and back-transfer rates.

Continuous-wave laser oscillation at 929nm from a Nd3+-doped LiNbO3:ZnO nonlinear laser crystal: A powerful tool for blue laser light generation

This work reports on room-temperature continuous-wave laser action at 929nm from a Nd3+:LiNbO3 nonlinear laser crystal co-doped with ZnO. The spectroscopic parameters of the quasi-three-level F3∕24→I9∕24 laser channel are discussed. In nonoptimal preliminary experiments, pump power at threshold was found to be as low as 105mW.

Influence of Nd^3+ and Yb^3+ concentration on the Nd^3+→Yb^3+ energy-transfer efficiency in the YAl_3(BO_3)_4 nonlinear crystal: determination of optimum concentrations for laser applications

The Nd3+→Yb3+ energy-transfer efficiency in the YAl3(BO3)4 nonlinear laser crystal has been investigated as a function of both donor (Nd3+) and acceptor (Yb3+) concentrations. An analytical expression giving the value of the energy-transfer rate for any Nd3+ and Yb3+ concentrations has been obtained on the basis of the analysis of experimental data. From this expression, a basic model is proposed to determine the Nd3+ and Yb3+ concentrations that optimize the Yb3+ output laser power obtained from a 808-nm diode-pumped Nd3+; Yb3+:YAl3(BO3)4 crystal.

Review Article: Modern developments in the physics of crystalline laser materials

The article [1] is a comprehensive review on recent advances in the development of novel lasing nano-crystalline ceramics as well as nonlinear crystals including organics for frequency converters. Several new attractive technologies in the physics and techniques of crystalline lasers are also discussed. Stimulated Raman scattering has been observed in metal-organic bis(guanidinium) zirconium bis(nitrilotriacetate) (GuZN-III), making this material promising for use as Raman laser converters. The cover picture is a projection of the unit cell of the GuZN-III single crystal along the [001] direction and its three structure fragments 2[C(NH2)3]+, H2O, and [Zr(NTA)2]2. The hydrogen bonding system is plotted by dashed lines for one selected guandinium and water molecule. Alexander A. Kaminskii is head of the Laser Crystal Physics Laboratory of the Institute of Crystallography and Director of the Joint Open Laboratory for Laser Crystals and Precise Laser Systems of the Russian Academy of Sciences. He is one of the leading researchers in physics and spectroscopy of insulating laser and nonlinear-laser crystals. Recently he has been elected member of the Editorial Board of physica status solidi (a).

Modern developments in the physics of crystalline laser materials

After a brief examination of known insulating laser crystals and the stimulated emission channels of their generating activator ions, this article reviews recent advances in the development of novel lasing nanocrystalline ceramics, as well as nonlinear and nonlinear-laser crystals, including organics, for χ(2) and χ(3) frequency converters. Several new attractive technologies in the physics and techniques of crystalline lasers are also discussed. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Spectroscopic study of Y b3+ centres in the Y Al3(BO3)4 nonlinear laser crystal

A spectroscopic study of Y b3+ ions in Y Al3(BO3)4 laser crystals is presented. Polarized absorption and site selective spectroscopy experimentsat low temperature have been used to determine the presence of two differentY b3+ centres in this host crystal in the concentration range 0.2–9 at.%. The contribution of thesecentres to the absorption spectra has been found to be dependent on the totalY b3+ concentration, and the Stark energy level diagrams corresponding to the differentY b3+ centres have been determined. The importance of electron–phonon coupling in the optical transitionsof Y b3+ ions has been also pointed out.

Nd3+→Yb3+energy transfer in theYAl3(BO3)4nonlinear laser crystal

The main properties of the ${\mathrm{Nd}}^{3+}\ensuremath{\rightarrow}{\mathrm{Yb}}^{3+}$ ${(}^{4}{F}_{3/2},{}^{2}{\stackrel{\ensuremath{\rightarrow}}{{F}_{7/2}}}^{4}{I}_{9/2},{}^{2}{F}_{5/2})$ energy transfer in yttrium aluminum borate nonlinear laser crystal have been studied. This host has been found especially suitable for efficient ${\mathrm{Nd}}^{3+}\ensuremath{\rightarrow}{\mathrm{Yb}}^{3+}$ energy transfer because of the good matching between phonon energy and the ${}^{4}{F}_{3/2}({\mathrm{Nd}}^{3+}{)\ensuremath{-}}^{2}{F}_{7/2}({\mathrm{Yb}}^{3+})$ energy gap (\ensuremath{\cong}1000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$). Energy-transfer probabilities in excess of 65% have been obtained for a ${\mathrm{Nd}}^{3+}$ (10 at. %) and ${\mathrm{Yb}}^{3+}$ (5 at. %) codoped sample. The influence of both crystal temperature and ${\mathrm{Nd}}^{3+}$ concentration on the transfer probability has been investigated. In the 15\char21{}350 K range the ${\mathrm{Nd}}^{3+}\ensuremath{\rightarrow}{\mathrm{Yb}}^{3+}$ energy-transfer efficiency increases with temperature, whereas for crystal temperatures above 350 K the ${\mathrm{Nd}}^{3+}\ensuremath{\leftarrow}{\mathrm{Yb}}^{3+}$ back transfer is activated, leading to a decrease in the effective ${\mathrm{Nd}}^{3+}\ensuremath{\rightarrow}{\mathrm{Yb}}^{3+}$ energy-transfer probability. The analysis of the decay curves obtained after pulsed excitation has been used to determine the multipole character of the ${\mathrm{Nd}}^{3+}\ensuremath{-}{\mathrm{Yb}}^{3+}$ interaction. The donor-acceptor energy-transfer microparameter was determined $[{C}_{\mathrm{DA}}({\mathrm{Nd}}^{3+}\ensuremath{\rightarrow}{\mathrm{Yb}}^{3+})\ensuremath{\cong}18\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}39}{\mathrm{cm}}^{6}/\mathrm{s}],$ and compared to those obtained for other ${\mathrm{Nd}}^{3+}\ensuremath{-}{\mathrm{Yb}}^{3+}$ co-doped materials.