Barium Borate Crystal Research Articles

Enhanced 355-nm generation using a simple method to compensate for walk-off loss

We theoretically and experimentally investigated a novel walk-off-compensation method for efficient ultraviolet beam generation. Through theoretical investigation, we described in detail how the power of a generated UV beam can be enhanced by the method; thus, we obtained a brief expression for the output power which has a prediction error of about 30%. In addition, we found that the beam quality can also be enhanced using this method. Through experiments using an alpha barium borate crystal as a walk-off compensator, we found that the power of the generated ultraviolet beam increased 1.9 times.

7.4 W yellow GaInNAs-based semiconductor disk laser

A high power frequency-doubled semiconductor disk laser emitting 7.4 W of output power at the yellow wavelength range is reported. Fundamental emission at around 1190 nm was achieved using a high quality gain mirror incorporating GaInNAs quantum wells. The infrared radiation was frequency doubled using an intracavity beta barium borate crystal. To the best of the authors knowledge, this is the highest output power reported for a single-chip semiconductor disk laser emitting yellow radiation.

Conical emission in β-barium borate under femtosecond pumping with phase matching angles away from second harmonic generation

The broadband parametric upconverted conical emission (CE) has been investigated in a β-barium borate crystal with phase matching angles away from second harmonic generation. A broad range of CE from 340 to 800 nm has been observed by varying the crystal thickness and the incident energy of the pump beam. It has been found that the tunability range can be increased with the thickness of the medium. The CE spectra and their angular positions have been measured and found to match with those calculated from recent theoretical models.

Athermal phase directions in barium borate crystals

Circular cones of propagation directions of ordinary or extraordinary waves exist in BaB2O4 crystals for which the phase of the wave remains constant when the crystal is heated. The axis of the cones is parallel to the optic axis of the crystal, while the cone half-angle at a wavelength of 532.1nm equals 77°16′ for the ordinary wave and 64°42′ for the extraordinary wave.

Formation and Quantification of Two-Photon Induced DNA Photolesions

The generation of DNA photolesions with a high degree of spatial confinement presents unique opportunities to study the recruitment of UV damage repair proteins to localized damage sites. Photolesion formation is typically accomplished by exposure to UV light which is difficult to manipulate with conventional optics, thus limiting the spatial control over the site of irradiation. As an alternative, we use two-photon absorption of visible light to mimic UV exposure in a form that can be manipulated by conventional optics. We frequency double the output of a tunable Ti:sapphire laser using a barium borate crystal to generate femtosecond pulses of 340-540 nm light. Sample irradiation is performed on 10-20μL volumes confined in a multiwell plate and scanned by a focused beam in a raster pattern through different axial planes. We have adapted a sensitive PCR-based assay to quantify the amount of two-photon induced damage. The assay is premised on a reduction in DNA transcription efficiency by the presence of bulky photolesions; decreased amplification of a sample relative to a control indicates the amount of damage. The assay and laser irradiation system are being tested on linearized pBR322 plasmid, and validated by comparison to direct UV exposure. Our preliminary results indicate that the degree of lesion formation exhibits a nonlinear dependence on power, which is in keeping with the intensity dependence expected for two-photon absorption. Additionally, maximal two-photon DNA damage occurs at wavelength lower than twice the single photon absorption maximum. We are analyzing our results to obtain quantitative information about the yield of photolesions generated by two-photon absorption.

Birefringence and absorption coefficients of alpha barium borate in terahertz range

In this paper we experimentally investigated the birefringence and absorption coefficients of alpha barium borate (α-BBO) crystal in the range of 0.3–10 THz by using a broadband air photonic terahertz time-domain spectrometer in both transmission and reflection modes. Several phonon modes were observed for o and e beams. The highest phonon mode at 6.8 THz has absorption coefficient of 1000 cm−1. The comparison between the optical properties of the α-BBO and beta barium borate crystals showed that their phonon frequencies are different and α-BBO crystal has smaller refractive index, birefringence, and absorption coefficients in low frequency region. The blueshift behavior of the lowest phonon of the α-BBO crystal over the temperature range of 10–293 K has also been characterized.

Terahertz-field-induced second-harmonic generation in a beta barium borate crystal and its application in terahertz detection

We report the observation of terahertz-field-induced second-harmonic (TFISH) generation in a beta barium borate (β-BBO) crystal based on a four-wave-mixing process. Using the conventional second-harmonic generation in the β-BBO crystal as a local oscillator, the crossed term between the TFISH and the local oscillator is proportional to the terahertz field. This phenomenon is used for coherent detection of intense terahertz waves, where a good linear response is observed for terahertz fields up to 160 kV/cm. In comparison, deviation from linear response and strong waveform distortion are observed when a 0.5-mm-thick ZnTe detector is used to characterize the same terahertz field.

Development of an optical parametric generator with pulsed dye amplification for high-resolution laser spectroscopy

An injection-seeded optical parametric generator (OPG), coupled with three pulsed dye amplification (PDA) stages, was shown to produce tunable, narrow linewidth laser radiation. The OPG was composed of a pair of beta barium borate (β-BBO) crystals and pumped by the third harmonic (355 nm) output of a seeded Nd:YAG laser. The OPG was injection-seeded at the idler wavelength (824 nm) using an external cavity diode laser (ECDL) with a mode-hop-free tuning range of 20 GHz. Using the PDA stages, the OPG output signal (624 nm) was amplified to 19 mJ/pulse, while maintaining a spectral linewidth of approximately 160 MHz at full-width-half-maximum (FWHM) which was within a factor of 2 of the Fourier limit. A system of lenses and apertures was used to minimize amplified spontaneous emission (ASE) in the PDA stages. Using the OPG/PDA system, two-photon laser-induced fluorescence measurements of atomic oxygen were performed by sum-frequency-mixing the 624-nm beam with the third harmonic output of the seeded Nd:YAG laser to generate approximately 1 mJ/pulse of ultraviolet radiation near 226 nm. Voigt line shapes were found to be in good agreement with oxygen atom spectra in atmospheric-pressure, laminar, counter-flow flames; the magnitude of Doppler and collisional broadening was approximately the same. The measured O-atom concentration profile was found to compare well with that calculated using an opposed-flow flame code.

Observation of birefringence in BBO crystals in the terahertz regime

We present experimental results of birefringence in beta barium borate (β-BaB 2O 4 or BBO) crystals in the 0.2–1 terahertz (THz) frequency range. Standard polarized THz-transmission spectroscopy of a BBO slab cut under 90° was performed at different azimuthal orientations to determine the ordinary and extraordinary refractive indices. An average Δ n/ n value of 0.118 was calculated. Moreover, azimuthal angle-dependent absorption was observed at about 0.65 THz, in close agreement with calculations based on first principles. Our calculations showed the absorption feature was due to the low-frequency phonon modes of the [B 3O 6] 3− rings. These results suggest that a BBO-based THz optical-parametric-oscillator design is feasible.

A low-loss, robust setup for double optical gating of high harmonic generation

Previously, a second harmonic field was added to a polarization gating field by a Mach–Zehnder interferometer to gate the high harmonic generation process in argon gas. To reduce the losses of the interferometer, we developed a collinear setup consisting of only two quartz plates and a barium borate crystal. The high intensity at the focus allowed the double optical gating to be performed on neon gas. As a result, a supercontinuous spectrum was produced capable of supporting 130as. There is no delay jitter between the second harmonic field and the polarization gating field associated in this setup, which is necessary for generating stable single isolated attosecond pulses.

Limits to compression with cascaded quadratic soliton compressors

We study cascaded quadratic soliton compressors and address the physical mechanisms that limit the compression. A nonlocal model is derived, and the nonlocal response is shown to have an additional oscillatory component in the nonstationary regime when the group-velocity mismatch (GVM) is strong. This inhibits efficient compression. Raman-like perturbations from the cascaded nonlinearity, competing cubic nonlinearities, higher-order dispersion, and soliton energy may also limit compression, and through realistic numerical simulations we point out when each factor becomes important. We find that it is theoretically possible to reach the single-cycle regime by compressing high-energy fs pulses for wavelengths lambda = 1.0-1.3 microm in a beta -barium-borate crystal, and it requires that the system is in the stationary regime, where the phase mismatch is large enough to overcome the detrimental GVM effects. however, the simulations show that reaching single-cycle duration is ultimately inhibited by competing cubic nonlinearities as well as dispersive waves, that only show up when taking higher-order dispersion into account.

Electrical and dielectric properties of β-BaB 2O 4 (BBO) and CsLiB 6O 10 (CLBO) crystals

In barium borate (BBO) crystals, sodium and potassium ions, inherited due to the preparation technique, are dominant charge carriers. The conductivity between layers is higher; the conductivity activation energy and the conductivity at 350 °C being equal to 1.01±0.05 eV and (1.3±0.2)×10 −8 S/cm, respectively. The conductivity activation energy and the conductivity at 350 °C along the channels are equal to 1.13±0.05 eV and to (4±0.2)×10 −9 S/cm, respectively. Relative static permittivity is almost isotropic, and equal to 7.65±0.05. Upon storing of cesium–lithium borate (CLBO) crystals, pre-heating to 600 °C eliminates the influence of surface humidity. At 500 K, the ionic conductivity ranges from 4×10 −12 to 2×10 −10 S/cm; the conductivity activation energy ranges from 1.01 to 1.17 eV. Relative static permittivity is equal to 7.4±0.3.

Carrier capture times of the localized states in an InGaN thin film with indium-rich nanocluster structures

A femtosecond nondegenerate pump-probe technique of using two beta barium borate crystals for frequency doubling a 7fs Ti:sapphire laser is used for studying the ultrafast carrier dynamics in an InGaN thin film, in which nanoscale indium-rich clusters have been observed. The carrier capture time of the localized states (the cluster states) from the free-carrier states (the states of the background compound) is calibrated. The initial rise times of the differential transmission of the probe intensity are calibrated to give the time constant of about 300fs for the degenerate cases over the whole photoluminescence spectral range and for the nondegenerate cases, in which both pump and probe wavelengths correspond to the free-carrier states. However, when the carriers are excited in the free-carrier states and probed in the localized states, the rise time increases to the range of 590–715fs, which represents the carrier capture time of the localized states from the free-carrier states.

Ultrasonic Investigation on Nanocrystalline Barium Borate (BBO) Glass Ceramics

Barium Borate (BBO) glasses containing different compositions of BaO and B2O3 with BaF2, Cr2O3 and TiO2 have been prepared by normal melting and annealing technique. The prepared bulk BBO glasses have been subjected to heat‐treatment. The heat‐treated BBO glasses produce nanophase BBO crystals in its structure. The existence of nanophase structure of the BBO crystals have been studied through XRD and the results reveal that the size of the particles is in the order of less than 100 nm. The SEM studies also support the observed XRD study and it explores the crystalline BBO crystal in the nano range. Further, the ultrasonic velocity, attenuation and their related parameters have been measured before and after heat‐treatment. The observed higher magnitude of variation in the ultrasonic parameters in nanophase glasses when compared with bulk glasses reveals a reduction in the particle size. The present investigation reveals that ultrasonics is one of the best tools to characterise the nanophase materials.

Femtosecond transient fluorescence spectrometer based on parametric amplification

We report an experimental proof-of-principle of a method for recording femtosecond, time-resolved fluorescence spectra in the visible range. The method is based on a noncollinear parametric amplification in a beta barium borate crystal and provides time resolution of the order of 100fs. We demonstrate that with this method, transient fluorescence spectra as wide as 6000cm−1 can be recorded in a single time-delay scan. Fluorescence decay dynamics and transient spectra of Coumarin 6dye dissolved in aniline were measured to test the usefulness of the method.

Effect of fluoride ions on the preparation of transparent glass ceramics based on crystallization of barium borates

Formation of transparent glass-ceramics based on crystallization of barium borate (BBO) crystals from BaO·B 2O 3 glass-systems, with and without addition of BaF 2 has been investigated. Crystallization of glass-samples was done by controlled thermal heat-treatment, at nucleation and crystallization temperatures, for different times and rates. When the glasses were heat-treated at the nucleation temperature, transparent glass-ceramics containing 0.1–0.3 μm BBO crystals were prepared. It is obvious that fluorine influences the transparency of glass-ceramics.

Colored conical emission by means of second harmonic generation in a quadratically nonlinear medium.

Colored conical emission was observed experimentally in a thick beta-barium borate crystal as a result of spatiotemporal modulational instability. In the presence of both dispersion and diffraction, colored conical emission showed specific features that were characteristic of the nonlinear dynamics of the strongly coupled fundamental and harmonic fields. Experimental observation directly demonstrated that beam angular spectra were substantially modified as a result of exponential growth of perturbations by means of parametric wave mixing. Seeded amplification of colored conical emission was demonstrated to support ultrabroadband up-conversion.

Optical parametric spectral broadening of picosecond laser pulses in β-barium borate

We present that optical parametric luminescence generated near the degenerate point of a type I optical parametric tuning curve in β-BaB2O4 can be used as a spectrally broadened probe beam for a picosecond pump-probe spectroscopy. In particular, we show that it is possible to change the position of the central peak and spectral range in visible and infrared wavelengths by varying the incident angle of pump pulse with respect to the optical axis of barium borate crystal. The picosecond time-resolved diffuse-reflectance experiment is also performed in order to demonstrate usefulness of these spectrally broadened pulses as a probe source.

Spectral interferometric optical coherence tomography with nonlinear β-barium borate time gating

A high-speed, all optical coherence tomography system was designed and constructed. This tomography system employs spectral interferometry and optical Fourier transformation to reduce the number of mechanical scanning dimensions required for multidimensional profilometry. The system also employs a time gate comprising a beta -barium borate crystal driven by a femtosecond laser pulse to improve measurement time. This system has 43-mum depth resolution and 150-fs temporal resolution and is capable of taking 1000 cross-sectional image frames per second.

The major problems of seeding and growth of barium borate crystals in terms of new data on phase relations in BaO–B 2O 3–Na 2O system

Differential-thermal analysis indicates that phase instability occurs in the majority of melt-solutions of the BaO–B 2O 3–Na 2O system, from which crystals of barium metaborate (BaB 2O 4, BBO) can be grown. Experiments show that the arising inhomogeneity of the crystallization medium accompanied by liquation phenomenon might result in faulty seeding and growth of BBO crystals, difficulties in controlled shaping, trapping of abundant inclusions, and other negative effects. The composition of the widely used solvent in growing BBO crystals (“eutectic” between the composition of BaB 2O 4 and BaB 2O 4·Na 2O) is unstable and tends to polyvariant transformations and, hence, is far from optimum. The compounds Na 4BaB 4O 9 and NaBO 2 might be the components that form pseudo-binary systems with BBO relative to stable melt-solutions promising for further technological processing.