Cesium Lithium Borate Research Articles

A Low-Wavelength Host Absorption Edge of Cesium-Lithium Borate CsLiB-=SUB=-6-=/SUB=-O-=SUB=-10-=/SUB=-

We have carried out an experimental study of the VUV edge of the optical host absorption of cesium-lithium borate crystals CsLiB6O10 (CLBO). The transmission (T=293 K) and absorption (T = 80, 293 K) spectra were studied, the short-wavelength edge of the transparency band (cutoff wavelength) and the energy position of the edge fundamental absorption at which the absorption coefficient k=50 cm-1 were determined. The absorption edge temperature shift coefficient -5.5·10-4 eV/K was determined. Based on low-temperature reflection spectra (T=10 K, theta=17o, E=7-30 eV) the Kramers-Kronig method was used to calculate the spectra of optical constants: refractive index (n) and absorption index (k), real (ε1) and imaginary (ε2) parts of the complex permittivity , as well as the absorption coefficient μ. The lowest energy peak, due to electronic transitions from the top of the valence band to the states of the bottom of the conduction band, was studied in the ε2(E) spectrum, the thresholds for interband transitions were determined Eg=7.95 eV. The origin of the fundamental absorption edge of cesium-lithium borate is discussed. Keywords:: Cesium-lithium borate CsLiB6O10 (CLBO), host absorption edge, optical properties.

Длинноволновый край фундаментального поглощения кристаллов цезий-литиевого бората CsLiB-=SUB=-6-=/SUB=-O-=SUB=-10-=/SUB=-

We have carried out an experimental study of the VUV edge of the optical host absorption of cesium-lithium borate crystals CsLiB6O10 (CLBO). The transmission (T = 293K) and absorption (T = 80, 293 K) spectra are studied, the short-wavelength boundary of the transparency band (cutoff wavelength) and the energy position of the edge are determined. fundamental absorption at which the absorption coefficient is k = 50 cm−1. The transmission (T = 293 K) and absorption (T = 80, 293 K) spectra were studied, the short-wavelength edge of the transparency band (cutoff wavelength) and the energy position of the edge fundamental absorption at which the absorption coefficient k = 50cm−1 were determined. The absorption edge temperature shift coefficient −(3–4.7)·10−4 eV/K was determined. The dependence of the absorption edge parameters of oriented LBO⊥ X and LBO⊥ Y crystals has been studied. Based on low-temperature reflection spectra (T =10K, θ =17◦, E = 4–32 eV ) the Kramers –Kronig method was used to calculate the spectra of optical constants: refractive index (n) and absorption index (k), real (ε1) and imaginary (ε2) parts of the complex permittivity , as well as the absorption coefficient μ. The lowest energy peak, due to electronic transitions from the top of the valence band to the states of the bottom of the conduction band, was studied in the ε2(E) spectrum, the thresholds for interband transitions were determined (Eg at T = 10K): 7.95 eV. The origin of the fundamental absorption edge of cesium-lithium borate is discussed.

Watt-level 193 nm source generation based on compact collinear cascaded sum frequency mixing configuration.

A compact, dual-stage, collinear-cascaded sum-frequency mixing configuration is presented for generating 193 nm sources. Due to the less-introduced, deep-ultraviolet optical components, the system is less prone to damage. In our proof-of-concept experiments, a 1030 nm laser and a 1553 nm laser synchronized to each other were used as drivers and an average power of ~0.7 W was obtained. For comparison, the noncollinear configuration gave an average power of 0.77 W. The difference of 0.07 W is attributed to the spatial walk-off inside the cesium lithium borate (CLBO) crystal, confirmed by indirect visualization. A possible way to overcome the small gap of 0.07 W is proposed for future work.

Record fifth-harmonic-generation efficiency producing 211 nm, joule-level pulses using cesium lithium borate.

The fifth harmonic of a pulsed Nd:YLF laser has been realized in a cascade of nonlinear crystals with a record efficiency of 30%. Cesium lithium borate is used in a Type-I configuration for sum-frequency mixing of 1053 and 266nm, producing 211nm pulses. Flat-topped beam profiles and pulse shapes optimize efficiency. The energies of the fifth harmonic up to 335mJ in 2.4ns pulses were demonstrated.

303 nm continuous wave ultraviolet laser generated by intracavity frequency-doubling of diode-pumped Pr3+:LiYF4 laser

We demonstrate an efficient and compact ultraviolet laser at 303 nm generated by intracavity frequency doubling of a continuous wave (CW) laser diode-pumped Pr3+:YLiF4 laser at 607 nm. A cesium lithium borate (CLBO) crystal, cut for critical type I phase matching at room temperature, is used for second-harmonic generation (SHG) of the fundamental laser. By using an InGaN laser diode array emitting at 444.3 nm with a maximum incident power of 10 W, as high as 68 mW of CW output power at 303 nm is achieved. The output power stability in 4 h is better than 2.85%. To the best of our knowledge, this is high efficient UV laser generated by frequency doubling of an InGaN laser diode array pumped Pr3+:YLiF4 laser.

Picosecond green and deep ultraviolet pulses generated by a high-power 100 kHz thin-disk laser.

We report on the generation of the second (515 nm) and fourth (257.5 nm) harmonics from a 100 kHz diode-pumped solid-state laser operating at a wavelength of 1030 nm which uses one Yb:YAG thin disk in the regenerative amplifier and delivers 60 W of the average output power in pulses of 4 ps duration. Thirty-five W in green light and 6 W in deep ultraviolet (DUV) were achieved. The sensitivity of the second harmonic generation efficiency toward the lithium triborate crystal temperature is demonstrated in experiment. The overall conversion efficiency from NIR to DUV of 10% was achieved. The β-barium borate and cesium lithium borate crystals were used as green to DUV convertors and compared regarding the efficiency and spectral bandwidths. The achieved output power is unique for DUV picosecond pulses.

Bandwidth analysis of type-I optical parametric chirped pulse amplification systems

We propose a set of empirical formulas to describe the signal broadband gain regime and ultra-broadband gain point under a given pump wavelength for a type-I optical parametric chirped pulse amplification (OPCPA) system. These formulas are applied in the usual nonlinear crystals (beta barium borate, potassium dihydrogen phosphate, deuterated potassium dihydrogen phosphate, cesium lithium borate, lithium triborate, and yttrium calcium oxoborate), and the corresponding results agree with numerically calculated ones. The empirical formulas provide guidelines for selecting appropriate crystals or pump wavelengths to design OPCPA for broadband or ultra-broadband gain bandwidths with appointed signal wavelength.

All solid-state 1917 nm deep-UV light source by seventh harmonic generation of an 888 nm pumped, Q-switched 1342 nm Nd:YVO_4 laser with excellent beam quality

In this paper we report on the realization of a deep-UV light source using the 1.3 μm transition of neodymium as pumping wavelength. The 191.7 nm radiation was obtained by generating the seventh harmonic of a high-power Q-switched 1342 nm Nd:YVO4 laser. A cesium lithium borate crystal was used for sum frequency mixing of the sixth harmonic and the fundamental. With a total of four conversion stages, up to 240 mW were achieved, with excellent beam quality at 155 mW (M2 < 1.7) and 190 mW (M2 < 1.9).

Humidity effect on hydration of CsLiB6O10 nonlinear optical crystal: X-ray diffraction study

Cesium lithium borate crystals (CLBO) grown from melt were kept under the relative humidity of 15–77%. At RH 45% or lower, water molecules are incorporated into CLBO structure resulting in symmetry reduction from I4¯2d to I4¯ without the loss of crystal quality. At higher humidity, crystal degradation is caused by the presence of liquid water on its surface as a result of capillary condensation.

Growth and characterization of Al-doped CsLiB6O10 crystal

To improve the hygroscopic nature of cesium lithium borate (CsLiB6O10, CLBO), the aluminum (Al) doping of CLBO crystal was investigated. By using the top-seeded solution growth (TSSG) method with a [001] direction seed, an Al-doped CLBO crystal with the dimensions of 60×58×24mm3 was grown from the self-flux system. The influence of Al doping on crystal growth and various properties of CLBO was discussed. The growth rate of CLBO crystal along the c direction was reduced by Al doping. Compared with undoped CLBO, the optical homogeneity and transmittance of Al-doped CLBO had no obvious change, but the hygroscopic nature of Al-doped CLBO was improved.

Development of a versatile high temperature top seeded solution growth unit for growing cesium lithium borate crystals

The design and fabrication of a state of the art high temperature top seeded solution growth (HTTSSG) unit with seed and crucible rotation options is discussed. Crystals from solid solutions of high viscosity could be grown using the setup. The fabricated setup is used to grow high optical quality single crystals of cesium lithium borate with dimensions 50x40x40 mm(3) for frequency conversion of ir to UV laser through harmonic generation.

Multiphoton absorption in CsLiB6O10 with femtosecond infrared laser pulses

Nonlinear absorption and refraction characteristics of cesium lithium borate (CsLiB6O10) crystal have been studied using Z-scan technique. Ti:sapphire laser with 110 fs pulse width operating at 800 nm wavelength and pulse repetition rate of 1 kHz is used as the source of photons. Intensity of the laser pulse is varied from 0.541 to 1.283 T W/cm2 to estimate the intensity dependence of multiphoton absorption coefficients. Using the theory of multiphoton absorption proposed by Sutherland [Handbook of Nonlinear Optics, in 2nd ed., edited by D. G. McLean and S. Kirkpatrick, Dekker, New York (2003)], found that open aperture Z-scan data fit well for the five-photon absorption (5PA) process. 5PA coefficients are obtained by fitting the expressions into the open aperture experimental data for various peak intensities (I00). The nonlinear refractive index n2 estimated from closed aperture Z-scan experiment is 1.075×10−4 cm2/T W at an input peak intensity of 0.723 T W/cm2. The above experiment when repeated with a 532 nm, 6 ns pulsed laser led to an irreversible damage of the sample resulting in an asymmetric open aperture Z-scan profile. This indicates that it is not possible to observe multiphoton absorption in this regime of pulse width using 532 nm laser.

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.

Growth and characterization of large CLBO crystals

A high optical quality Cesium lithium borate (CLBO) crystal with dimensions of 146×132×118 mm was grown by the Kyropoulos method. The 4th harmonic generation of a frequency doubled Nd:YAG laser, from 532 to 266 nm, was carried out with a CLBO crystal doubler, and an average output power of 28.4 W was achieved at 266 nm. Polished surfaces were etched to reveal the cracking mechanism of CLBO crystals. Through observation and comparison of the surface etching patterns, it is proved that CLBO crystals crack under chemical attack by water molecules penetrating from the (1 0 0) and (0 1 0) crystallographic planes.

Growth and calorimetric measurements on CsLiB 6O 10

Single crystals of cesium lithium borate (CLBO) were grown from stoichiometric melt, as well as from B 2O 3 deficient flux. Calorimetric measurements performed on the grown crystals show that the material transforms to glassy phase from the molten phase even at cooling rates as low as 1 °C/min. The transformation to the crystalline phase from the glass phase does not occur during the heating cycle in the DTA experiments. In order to estimate the onset of crystallization temperature of CLBO glass and ensure the appearance of crystallization peak during heating cycle, a new approach (seeded crystallization) was adopted in the DTA experiments. The onset of seeded crystallization temperature shows a strong dependence on the heating and cooling rates. The activation energy of seeded crystallization determined by Kissinger method turns out to be 3.07 eV. The ergodicity making (EM) of the glass transition as seen from the DSC measurement is ∼ 424 °C for a heating rate of 5 °C/min. Microscopic examination suggests that the glass CLBO transforms to crystalline phase via. dendrites.

Study on Ultra-Precise Machining of CLBO Crystal

Cesium Lithium Borate (CsLiB6O10 or CLBO) is the most effective non-linear crystal which generates ultraviolet harmonics of the Nd:YAG fundamental laser wavelength. In order to enhance the damage threshold, low CLBO surface roughness, by ultra-precision machining, is needed. Because the CLBO crystal has easy hydroscopic reaction and micro scratches in machining, ultra-precise machining of the CLBO crystal is a difficult technical problem. In this paper, the new lapping slurry and polishing slurry are introduced. And the deliquescence degree of CLBO is fallen to lowest. A new working technology is also adopted. After rough polishing, the concentration of ultra-precision polishing slurry is increased properly. So does the ultra-precision polishing speed, and the wiping speed is faster than the deliquescence speed. The CLBO crystal surface roughness can achieve 1nm and keep the surface quality well.

Degenerated optical parametric chirped-pulse amplification with cesium lithium borate

A gain amplifier for degenerated optical parametric chirped-pulse amplification (OPCPA) with lithium triborate and cesium lithium borate (CLBO) crystals was demonstrated in a near-collinear configuration. The signal gain of the final energy amplifier with CLBO was approximately 6. After compression, the 123 fs pulse duration was obtained. Compared with potassium dihydrogen phosphate, it is confirmed that CLBO is more effective as a nonlinear crystal in a final power amplifier for terawatt or petawatt OPCPA systems. To our knowledge, this is the first demonstration of OPCPA with CLBO.

Noncritically phase-matched second-harmonic generation in cesium lithium borate.

Efficient generation of 236-nm light was demonstrated by use of noncritically phase-matched second-harmonic generation in cesium lithium borate. Noncritical phase matching provided approximately 20x the nonlinear drive for second-harmonic generation than beta-barium borate for 236-nm generation. The 236-nm wavelength is the fourth harmonic of a 946-nm Nd:YAG laser. Phase matching was accomplished at a crystal temperature of -15 degrees C.

Absolute non-linear optical coefficients measurements of CsLiB6O10 single crystals by second harmonic generation

Abstract We present absolute measurements of the effective non-linear optical coefficients d eff of cesium lithium borate crystals (CsLiB 6 O 10 , CLBO) by second harmonic generation using a continuous Nd-YAG laser source. The experiments were carried out at room temperature, on crystals cut perpendicular to type I or type II phase matching directions, with two different crystal lengths along the propagation direction. The d 36 and d 14 non-linear coefficients involved in d eff developments are deduced and are shown to be equal as it is predicted by the Kleinman symmetry. Two different compositions prepared by the Czochralski technique from melt with compositions of 1:1:6 and 1:1:5.5 molar ratios of Cs 2 O, Li 2 O and B 2 O 3 are comparatively studied.

Effect of melt composition on the electrical conductivity and IR absorption of CsLiB6O10 crystals

AbstractThe dc conductivity of cesium lithium borate crystals grown from different melt composition has been studied in the 50 – 750 °C range. The temperature dependence of the electrical conductivity followed the Arrhenius law in most cases. The anisotropy of the electrical conductivity of crystals was rather small. The vibrational modes of water molecules present in the crystals were detected by infrared absorption technique. It was found that the intensity of the two OH stretching vibrational bands depends on the thermal history of the crystals, and, beside the two main water bands, some additional weak lines appear at –185 °C in the crystals with low Cs/B ratio.