Rukang Li

Nonlinear Optical Borate Crystals, Principles and Applications

Preface INTRODUCTION History of the Theoretical Understanding for Nonlinear Optical Crystals History of Development on Nonlinear Optical Borate Crystals Crystal Growth of Nonlinear Borate Crystals and Current Status of Applications THEORETICAL BASIS TO DEVELOP BORATE NONLINEAR OPTICAL CRYSTALS BORATE NONLINEAR OPTICAL CRYSTALS FOR FREQUENCY CONVERSION BBO LBO Family KBBF Family Other Borate Crystals Borate Crystals in Developing APPLICATIONS Rapid Proto-Typing Semiconductor Industry - Bia-Hole Drilling - Annealing - Marking - Inspection Bio-Medical Applications - Eye Surgery - Protein Processing Advanced Instrument Making

Chemical engineering of a birefringent crystal transparent in the deep UV range

A new birefringent Ba2Mg(B3O6)2 (BMBO) crystal with dimensions of 41 × 27 × 9 mm3 has been grown from a stoichiometric melt. The structure of BMBO, determined from single-crystal X-ray diffraction data, demonstrates that it belongs to the rhombohedral space group R with unit cell parameters of a = 7.094(5) A, c = 16.721(15) A and Z = 3. BMBO melts congruently with a melting point of 1000 °C and does not show any phase transitions from room temperature to the melting point. It is found that the BMBO crystal has a wide transmission range (178–3000 nm), large birefringence (Δn = no − ne = 0.2045–0.0767 from 190 nm to 3 μm) and high chemical stability. The BMBO crystal may serve as a unique birefringent crystal for polarizers, beam displacers and beam splitters in the ultraviolet, especially in the deep ultraviolet range.

167.75-nm vacuum-ultraviolet ps laser by eighth-harmonic generation of a 1342-nm Nd:YVO4 amplifier in KBBF.

We demonstrate a ps 167.75-nm vacuum-ultraviolet (VUV) laser by cascaded second-harmonic generation (SHG). The VUV laser is produced by eighth-harmonic generation (EHG) of a mode-locked ps 1342-nm Nd:YVO4 amplifier through three stages cascaded SHG with two LiB3O5 crystals and one KBe2BO3F2 crystal, successively. The 167.75-nm laser provides up to 65-μW output power, and the corresponding photon flux and photon flux density are 5.5×10(13)  s(-1) and 1.6×10(18)  s(-1)·cm(-2), respectively.

Two new barium borate fluorides ABa12(BO3)7F4 (A = Li and Na).

Two new barium borate fluorides LiBa12(BO3)7F4 and NaBa12(BO3)7F4 are obtained by spontaneous crystallization from high-temperature flux. The two compounds are isostructural and crystallized into the tetragonal system, I4/mcm space group, with unit cell parameters of a = 13.5709(6) Å, c = 14.9908(13) Å for LiBa12(BO3)7F4 and a = 13.6443(9) Å, c = 15.021(2) Å for NaBa12(BO3)7F4. Isolated Li/NaF4-BO3 units formed by Li/NaF4O square pyramids and B3O3 groups sharing the O5 atom are found occupying the octagonal tunnels built by Ba and BO3 groups along the c axis. High mobility of Li(+) ion is observed in the LiBa12(BO3)7F4 single crystal by ac impedance measurements at different temperatures.

On the calculation of refractive indices of borate crystals based on group approximation

Abstract A calculation method for the refractive indices of borate crystals based on anisotropic polarizabilities of anionic groups is proposed. Firstly the polarizabilities of some model groups are obtained from dipole-dipole approximation and then the environment parameters of different groups are obtained from least square fit of the refractive indices of well known optical crystals. This simple method can give accurate calculated refractive indices with errors not more than 3% in comparison with experimental values. Examples of applications of this method are shown to be successful in explaining the enhanced anisotropy of the KBe2BO3F2 family crystals, predicting refractive indices with the solid solution systems with fine tuned chemical compositions and designing new birefringent crystals suitable for the deep ultraviolet range.

A bright continuous-wave laser source at 193 nm

This Letter reports on the realization of a highly coherent light source at 193 nm. By frequency-quadrupling an amplified diode laser, over 15 mW of laser emission could be generated using the nonlinear crystal potassium fluoro-beryllo-borate. The high stability of the setup was proven in an 80 h-measurement, and the impact of the crystal transmission on the output power was thoroughly studied. This laser source is an ideal tool for photoemission spectroscopy and reaches the power level to replace excimer lasers in metrological applications.

1.3-mW tunable and narrow-band continuous-wave light source at 191 nm

We report on the realization of a continuous-wave light source based on nonlinear interaction in KBBF at a wavelength of 191 nm. More than 1.3 mW of deep-ultraviolet power was generated in a mechanically robust setup pumped by an amplified grating stabilized diode laser. Mode hop-free tuning over 40 GHz at 191 nm could be demonstrated.

2.14 mW deep-ultraviolet laser at 165 nm by eighth-harmonic generation of a 1319 nm Nd:YAG laser in KBBF

We report a nanosecond (ns) 165 nm deep-ultraviolet (DUV) laser with a maximum average power of 2.14 mW by eighth-harmonic generation (EHG) of a homemade ns 1319 nm Nd:YAG laser. The EHG was performed by cascaded second-harmonic generation (SHG) through successive stages of two LiB3O5 crystals and one KBe2BO3F2 crystal. The generated radiation at 165 nm is the shortest DUV wavelength ever generated through SHG method and the highest average power of all solid state lasers below 170 nm to our knowledge. Such a ns DUV laser at 165 nm is of great interest for photoemission spectroscopy and Raman spectroscopy.

Thermo-physical properties of nonlinear optical crystal K3B6O10Br

The thermo-physical properties of the nonlinear optical (NLO) crystal K3B6O10Br (KBB) were experimentally investigated, including specific heat, thermal conductivity, coefficient of thermal expansion and refractive index. The specific heat of KBB is lower than that of LiB3O5 and higher than that of other borate NLO crystals, such as β-BaB2O4, CsLiB6O10 and CsB3O5, and KBB manifests a high damage threshold because of its lower temperature gradient during laser pulse irradiation. The thermal expansion coefficients were obtained as αx = 5.09 × 10−6 K−1 and αz = 2.39 × 10−5 K−1, showing weaker anisotropy than those of commonly used NLO crystals. The temperature-dependent Sellmeier dispersion equations of the refractive indices were also obtained, and the phase-matching angles for second harmonic generation (SHG) at temperatures of 313, 343, 373, 403 and 433 K which were calculated from these equations are in good agreement with the experimental values. All results are indicative of the KBB crystal as a novel promising NLO crystal for high power SHG.

High average power third harmonic generation at 355 nm with K 3 B 6 O 10 Br crystal

We demonstrate a nanosecond 355 nm laser by third harmonic generation of an Nd: YAG laser with a 4 × 4 × 13.3 mm3 type I cut K3B6O10Br crystal for the first time. The maximum average power of 19.3 W is achieved with the corresponding conversion efficiency of 16.3% and the maximum conversion efficiency of 18.3% is recorded when the 355 nm average power is 15.8W. In addition, several nonlinear optical parameters including the angle and temperature bandwidths at third harmonic generation are also investigated.