Borate Nonlinear Optical Crystals for Frequency Conversion

Abstract

After the discovery of BBO and LBO during 1979-1987, many research groups are involved in this field because the borate NLO crystals have several outstanding advantages, such as the relative larger second harmonic generation (SHG) coefficients, wide transparent spectral range on the UV side, high damage threshold, and so on. As a result, more than 20 borate NLO crystals have been discovered till now. In this chapter, we will introduce several typical borate crystals, which have indicated important applications, particularly in laser industry. These borate crystals include (1) b-BaB 2 O 4 (BBO), the basic structural unit of which is (B 3 O 6 ) 3À group. (2) LiB 3 O 5 (LBO) family, including CsB 3 O 5 (CBO) and CsLiB 6 O 10 (CLBO), the basic structural unit of which is (

Sr2Pb(BeB5O10)(BO3): An Excellent Ultraviolet Nonlinear-Optical Beryllium Borate by the Pb-Modified Construction of a Conjugated System and Lone-Pair Effect

“…Crystal materials with an ultraviolet (UV) nonlinear-optical (NLO) property can emit coherent and tunable laser beams by cascading second-harmonic-generation (SHG) methods, constituting the core part of solid-state laser systems. − UV laser sources have drawn extensive science and technology applications including laser medical treatment, material micromachining, and semiconductor manufacturing. − To achieve promising UV NLO materials, strict requirements should be satisfied simultaneously: (i) acentric crystal structures to induce a SHG response; (ii) a broad transparency range below a light wavelength (λ) of 300 nm (or E g > 4.13 eV); (iii) a large SHG efficiency [≥1 × KH 2 PO 4 (KDP)] beneficial to increasing the frequency conversion efficiency of the laser; (iv) sufficient birefringence (Δ n ) between about 0.07 and 0.1 for phase-matching ability; (v) high laser-induced damage threshold (LIDT) for a laser system with high power radiation; (vi) an easily grown large single crystal. However, integrating all of the good qualities into one crystal is challenging because a mutually conflicting nature exists between the SHG efficiency and E g and between birefringence and E g .…”