5.32 W ultraviolet laser generation at 266†nm using sum-frequency method with CsB3O5 crystal.

Ultraviolet (UV) beam generation at 266 nm using the sum-frequency (SFG) method with CsB3O5 (CBO) crystals was first suggested in 1997 [Opt. Lett.22, 1840 (1997).10.1364/OL.22.001840]; however, there has been no further research in the past 25 years. Herein, by sum-frequency mixing in CBO crystals, we obtained a high conversion efficiency picosecond (ps) and a high-power nanosecond (ns) 266 nm UV beam output. First, a ps laser device with simultaneously radiated wavelengths of 1064 and 355 nm and repetition frequency of 10 Hz was used as the fundamental laser source, and the conversion efficiency from 1064 + 355 nm to 266 nm reached 20.35%. We then used a 1064 nm ns laser with a high output power and repetition frequency of 10 kHz as the pump source. We accurately modified the optimal phase matching direction of the CBO crystal, and the achieved output power at 266 nm reached 5.32 W.

Improvement on Magnetocaloric Effect through Structural Evolution in Gadolinium Borate Halides Ba2Gd(BO3)2X (X = F, Cl).

A new Gd3+-containing borate Ba2Gd(BO3)2F has been successfully grown via the high-temperature solution method using BaF2-NaF-B2O3 flux. Ba2Gd(BO3)2F crystallizing in the orthorhombic space group Pnma is with lattice parameters a = 7.571(4) Å, b = 10.424(5) Å, c = 8.581(4) Å, α = ß = γ = 90°, and Z = 2. Its three-dimensional framework was constructed from interesting pinwheel-like [Gd(BO3)F]∞ layers bridged by sharing [BO3]3-, which is different from the [Gd(BO3)]∞ layer in the model structure Ba2Gd(BO3)2Cl. The magnetic measurements indicated that Ba2Gd(BO3)2F has a larger magnetocaloric effect with -ΔSm,max = 27.82 J·kg-1·K-1at 2 K and 9 T than that of Ba2Gd(BO3)2Cl under the same conditions. Moreover, thermal stability, infrared spectrum (IR), and ultraviolet-visible-near-infrared diffuse reflectance spectrum were carried out to characterize the title compounds. The first-principles computations also looked into the electronic band structures, densities of states, and refractive indices.

Sr14.06Gd14.63(BO3)24: A Gadolinium-Rich Borate with Magnetic Refrigeration Performance.

A single crystal of Sr14.06Gd14.63(BO3)24 has been successfully grown through a high-temperature solution technique with K2O-KF-B2O3 as the flux. It crystallizes in the Pnma space group with parameters a = 22.3153(5) Å, b = 15.9087(4) Å, c = 8.7507(2) Å, and Z = 2. Sr14.06Gd14.63(BO3)24 has a three-dimensional (3D) framework built from [GdO] chains, in which the isolate [BO3]3- groups and Sr2+ ions fill in the space of the 3D framework. The magnetic measurements revealed that the title compound exhibits a large magnetocaloric effect with the magnetic entropy change of -ΔSm = 42.2 J kg-1 K-1 at 2 K for 7 T, which is higher than that of the commercial material, Gd3Ga5O12 (GGG), with -ΔSm of 38.4 J kg-1 K-1 under the same conditions. Moreover, the infrared spectrum (IR), UV-vis-NIR diffuse reflectance spectrum, and thermal stability were investigated.

Growth, Structure, and Properties of a Multifunctional Crystal Pr2CaB10O19.

A new praseodymium-based borate crystal Pr2CaB10O19 (PCB) has been grown through the high temperature solution method. PCB crystallizes in monoclinic space group C2 with unit cell parameters of a = 10.9475(10) Å, b = 6.5343(7) Å, c = 9.0336(8) Å, ß = 91.652(3)°, and Z = 2, in which B5O12 groups and PrO10 and CaO8 polyhedra constitute the three-dimensional framework. PCB exhibits a similar second harmonic response intensity to that of La2CaB10O19 and an intense orange fluorescence emission with a long fluorescence lifetime at about 610 nm excited by a xenon lamp light of 466 nm. The band gap, partial density of states, and birefringence have been investigated via theoretical calculations.

Deep-Ultraviolet Nonlinear Optical Crystal Cs2 Al2 (B3 O6 )2 O: A Benign Member of the Sr2 Be2 (BO3 )2 O Family with [Al2 (B3 O6 )2 O]2- Double Layers.

For the explorations of deep ultraviolet (DUV) nonlinear optical (NLO) borates, a type of important optoelectronic material, the (BO3 )3- group has been long regarded as the sole microscopic optically-active unit, and toxic Be-containing raw materials are frequently-adopted. Herein, a new DUV NLO crystal, Cs2 Al2 (B3 O6 )2 O (CABO), was designed and synthesized by simultaneously replacing the (BO3 )3- groups and Be2+ cations for (B3 O6 )3- units and Al3+ cations in Sr2 Be2 (BO3 )2 O, which possesses a favorable structure, through a chemical co-substitution approach. CABO exhibits a considerable DUV NLO capability because of the wide band gap and large birefringence originating from the [Al2 (B3 O6 )2 O]2- double layers. Remarkably, CABO melts congruently and does not contain the toxic beryllium, which is favorable for bulk-size crystal growth and practical applications.

High-energy noncollinear optical parametric-chirped pulse amplification in LBO at 800 nm.

The optical parametric-chirped pulse amplification (OPCPA) based on large-aperture nonlinear optical crystals is promising for implementation of an ultrahigh peak-power laser system of 10 PW and beyond. We demonstrated the highest energy broadband OPCPA at 800 nm, to the best of our knowledge, by using an 80 mm in diameter LiB(3)O(5)(LBO) amplifier, with an output energy of 28.68 J, a bandwidth of 80 nm (FWHM), and conversion efficiency of 25.38%. After compression, a peak power of 0.61 PW with 33.8 fs pulse duration is produced.