Lithium Iodate Crystals Research Articles

(H3O)Li2(IO3)3: crystal structure and IR spectrum

The synthesis, IR spectroscopy, thermal and UV-Vis transmittance of the new lithium iodate crystal: (H3O)Li2(IO3)3, were studied. The crystal structure of (H3O)+·2(Li)+· 3(IO3)- was determined by single-crystal X-Ray diffraction analysis at 100(2) K. It crystallizes in the monoclinic system (P21/n) with the parameters: a = 8.3266(12) Å, b = 10.9893(17) Å, c = 11.2472(17) Å, α = γ = 90°, β = 111.360(4)° and Z(Z') = 4(1). The structure contains a hydronium cation (H3O)+, three crystallographic independent trigonal pyramidal IO3 anions, and two independent cations (Li)+ coordinated each by four oxygen atoms 3(IO3)- at the apices of strongly deformed tetrahedrons. The research results have revealed the mechanisms of crystal formation and the characteristic absorption bands of functional groups, which are of scientific importance. The possibility of the existence of certain properties is also discussed.

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.

Application potential of paratellurite and iodic acid crystals for acousto-optics in the Terahertz range

The possibility of applying paratellurite, iodic acid, and lithium iodate crystals in acousto-optics in the THz range has been investigated. The transparency windows of these crystals and their refractive indices in the THz range have been determined. The acousto-optic figures of merit of these materials are calculated for different acousto-optic interaction geometries.

Giant nonlinear optical activity in a plasmonic metamaterial

In 1950, a quarter of a century after his first-ever nonlinear optical experiment when intensity-dependent absorption was observed in uranium-doped glass, Sergey Vavilov predicted that birefringence, dichroism and polarization rotatory power should be dependent on light intensity. It required the invention of the laser to observe the barely detectable effect of light intensity on the polarization rotatory power of the optically active lithium iodate crystal, the phenomenon now known as the nonlinear optical activity, a high-intensity counterpart of the fundamental optical effect of polarization rotation in chiral media. Here we report that a plasmonic metamaterial exhibits nonlinear optical activity 30 million times stronger than lithium iodate crystals, thus transforming this fundamental phenomenon of polarization nonlinear optics from an esoteric phenomenon into a major effect of nonlinear plasmonics with potential for practical applications.

Photon coincidences in spontaneous parametric down-converted radiation excited by a blue LED in bulk LiIO_3 crystal

We report on experimental and numerical investigation of two-photon coincidence properties of the parametric spontaneous down-converted field excited by a high brightness blue LED in bulk lithium iodate crystal. Ratio of up to 11.5% of coincidence, which cannot be attributed to classical coincidences, to single photon counts was recorded at the outputs of multimode fibers, demonstrating well-preserved biphoton property. This result, combined with practically useful power of the source, suggests its possible application for a class of quantum experiments.

Sum-frequency mixing of radiation from two extended-cavity laser diodes using a doubly resonant external cavity for laser cooling of trapped ytterbium ions

Over 100 μW of continuous-wave tunable ultraviolet radiation at 370 nm is generated by the sum-frequency mixing of radiation from two extended-cavity laser diodes having powers of 60 mW at 822 nm and 8 mW at 671 nm in a lithium iodate crystal. The crystal is placed in an external cavity that enhances the powers of two fundamental beams simultaneously by approximately 40. This light source is successfully applied to the laser cooling of trapped ytterbium ions.

Dielectric studies of a α-LiIO3 crystals grown from neutral and alkaline solutions

The dielectric properties of lithium iodate crystals of the hexagonal modification grown from solutions with pH = 6.2, 7.1, and 11.0 in the frequency range from 25 Hz to 1 MHz at temperatures of 290–420 K were investigated. The temperature dependence of the imaginary part of the permittivity was found to exhibit clearly pronounced relaxation peaks originating from ionic mobility. The shift in the position of the relaxation maxima was used to calculate the activation energy and attempt frequency for mobile ions. The Cole-Cole diagrams revealed the existence of a spectrum of relaxation times. The presence of the specific feature in the ionic mobility of lithium iodate crystals grown from solutions with pH ∼ 7 was confirmed.

High-frequency broadband transducers of ultrasonic oscillations

The amplitude-frequency responses (AFRs) of ultrasonic oscillation transducers based on piezoelectric lithium iodate crystals of hexagonal modification and on magnetic soft ferrite powders are experimentally studied. The possibility to control the efficiency of magnetostriction powder transducers (MPTs) by variation in the value and orientation of the external magnetic field is shown. Results of measurements of the transformation efficiency for ferrites of various chemical compositions are presented.

Effect of fundamental radiation wave front astigmatism on the process of second optical harmonic generation in uniaxial crystals

Nonlinear processes of conversion of radiation with wave front astigmatism in nonlinear crystals of 6 and 3m symmetry are theoretically analyzed. Spatial-angular and energy structures of the second optical harmonic in lithium niobate and iodate crystals are investigated theoretically and experimentally.

Nonlinear frequency conversion of radiation of a focused Gaussian beam

Nonlinear conversion of radiation of a Gaussian beam focused by a lens possessing coma aberration is theoretically analyzed for nonlinear crystals of 6, 4, 4¯ symmetry group. With the help of computer modeling, spatial-angular and energetic structures of fundamental radiation on the crystal face and of the second optical harmonic in a lithium iodate crystal are obtained.

Fluorine-containing polysiloxane coatings for lithium iodate crystals

Fluorine-containing polysiloxane coatings for lithium iodate crystals

Polarization ring interferometers and their use for studying nonreciprocal optical effects

Based on the method of Jones matrices, we consider the optical properties of a polarization ring interferometer and show the possibility of its use for studying various nonreciprocal effects. Using such an interferometer, we measure nonreciprocal magnetooptical linear birefringence in a lithium iodate crystal.

SFM and EFM Studies on a Clay-Based Dielectric Nanocomposite

A Laponite clay-based lithium iodate nanocomposite has been synthesized for non-linear optical applications. The surface morphology of dip-coated optical waveguides were analysed by Scanning Force Microscopy (SFM) techniques. Individual Laponite particles were first imaged by using Intermittent-Contact Atomic Force Microscopy on pure Laponite layers. Electrostatic Force Microscopy was then used on nanocomposite waveguides in order to obtain a “chemical contrast” of sample surface. The strong electrical contrast observed was attributed to sample topography and not to the different properties of each nanocomposite constituent. Finally, in ambient conditions, dip-coated layers were also shown to be sensitive to humidity which leads to the occurrence of surface lithium iodate crystals with sub-micrometer size.

Photoinduced Properties of Lithium Niobate, Tantalate, and Iodate Crystals

General aspects of optical (photorefractive) damage to LiNbO3, LiTaO3, and LiIO3 single crystals are analyzed. These compounds possess no semiconducting properties, and, as a consequence, the photorefractive effect in them defies classical description. A model for the optical-damage zone is proposed which is based on the hypothesis that this zone has an ordered, quasi-electret structure. The influence of high-intensity illumination on the properties of crystalline dielectrics is described analytically, and the effect of polymorphism on the photorefraction and photovoltaic conduction in such materials is analyzed. It is shown using LiNbO3 and LiIO3 as examples that the proposed approach is applicable to both single crystals of stoichiometric compounds and doped crystals.

Cascading second-order versus direct third-order nonlinear optical processes in a uniaxial crystal

We present an experimental and theoretical study of sum-frequency generation of two infrared photons and one visible photon in a lithium iodate crystal. The sum-frequency light can be generated directly in a third-order process as well as in two subsequent second-order processes. By comparing experimental results to numerical and analytical calculations, we demonstrate that the three possible cascading processes, i.e. two second-order cascading processes with phase matching in either the first or the second step and a cascading process with overall phase matching with both steps equally mismatched, are comparable in intensity to the direct third-order process. Polarization and angular-dependent measurements are used to assign the different processes. By using a spectrally broad infrared pulse and a spectrally narrow visible pulse we investigate the possibility of using the spectrally resolved nonlinear signals as a tool to unravel their origin. For the cascading processes, phase matching of the first step results in a spectrally broad sum-frequency signal while overall and second step phase matching give rise to a narrow signal.

Frequency-doubled diode laser for ultraviolet absorption spectroscopy at 325 nm

A frequency-doubled tunable diode laser for absorption spectroscopy in the ultraviolet is described. The device is based on an external cavity diode laser with a transmission grating. Second-harmonic generation at 320–327 nm is carried out using a lithium iodate crystal. The measured single-pass cw ultraviolet power is 60 nW and the system has a 40-GHz continuous mode-hop-free tuning range in the ultraviolet. The laser was demonstrated by measuring the 324.75-nm 42S1/2–42P3/2 transition of copper at atmospheric pressure with a single continuous scan.

LiIO3: growth and properties for optical and photoluminescent applications

Abstract Lithium iodate crystals (α-LiIO3) exhibit large piezoelectric, elasto-optic and non-linear optical effects. Indeed, the high non-linear coefficients of this material make it very useful for second harmonic generation and frequency mixing (d31 and d33 lying between −6 and −7×10 −12 V −1 m for wavelength between 1.06 and 2.12 μm ) [1] , [2] . Moreover, its very large transparency range [3] from 300 nm to 5 μm is very interesting for applications in the IR range. Our present studies concern physical characterizations of this material: • the phase transitions versus temperature have been studied by differential thermal analysis, thermogravimetry and X-ray measurements [4] ; • dielectric measurements versus temperature, by using the impedance spectroscopy technique, have led to a better understanding of the ionic conduction process occurring in α-LiIO3 [5] and optical applications: • waveguides have been realized in this material by ionic (H+) implantation [6] ; • photoluminescence studies have been performed in Cr3+ doped crystals. After a short description of the growth technique, results concerning photoluminescence are developed.

Relaxation phenomena in lithium iodate crystals

Ionic conductivity of lithium iodate crystals grown in various conditions has been studied in the polar c-axis direction. The dielectric response at room temperature is associated with relaxation of space charges. The temperature dependence of the dc ionic conductivity shows quite different activation energies in the range 35–470 K which are well related to the doping and acidity of the growth solution.

Quantum-efficiency measurement of photodetectors by means of correlated photons

We report the first results obtained at the Istituto Elettrotecnico Nazionale Galileo Ferraris of quantum-efficiency measurements of actively quenched avalanche photodiodes in the photon-counting regime. The measurements were performed with the technique of correlated photons generated by a parametric downconversion process in a nonlinear crystal of lithium iodate, an absolute technique that does not require any standard. We pay special attention to the problem of alignment of the optical bench and to the implementation of a parametric amplifier scheme with a diode-laser source. The technique is described, and results of quantum-efficiency measurements of two photodiodes are presented.

Parametric amplification for radiance measurements

This paper presents the first results of parametric amplification obtained at the Istituto Elettrotecnico Nazionale G. Ferraris (IEN) at a wavelength of 633.5 nm in a crystal of lithium iodate, pumped by an argon laser at a wavelength of 351 nm and injected by a diode laser at 788.2 nm in the noncollinear phase-matching case. Amplified and spontaneous parametric signals around 633 nm were measured in a photon-counting setup, at different powers of both the argon and the diode laser. This experiment is preliminary to the absolute radiance measurement of a thermal source.