Nonlinear Optical Crystals: A Complete Survey

The development of nonlinear optical (NLO) borate crystals for generation of visible and UV light is reviewed. We first discussed on the basic principles of laser frequency conversion. Then, we examine the trends in research on NLO crystals. The background and present status of NLO borate crystals are summarized. The main considerations are focused on the discussion of crystals like CsLiB6O10 (CLBO), GdxY1−xCa4O(BO3)3 (GdYCOB) and K2Al2B2O7 (KAB). Properties of related materials like β-BaB2O2 (BBO), LiB3O5 (LBO), KBe2BO3F2 (KBBF), Sr2Be2BO7 (SBBO), CsB3O5 (CBO), GdCa4O(BO3)3 (GdCOB) and YCa4O(BO3)3 (YCOB) are included for comparison. We aim to provide a complete view of developing a new NLO borate material for actual laser applications. This review covers various aspects including the search for new materials, the growth of bulk crystals, the characterization of crystal properties as well as the development of new techniques to overcome obstacles in actual laser application, namely, thermal dephasing and laser-induced damage. Finally, perspectives on NLO borate crystals and all-solid-state UV lasers are evaluated.

Recent development of nonlinear optical borate crystals: key materials for generation of visible and UV light

The primary goal of this review is to present a clear chemical perspective of borates in order to stimulate and facilitate the discovery of new borate-based optical materials. These materials, whic...

Borates: A Rich Source for Optical Materials.

Nonlinear optical (NLO) crystals are essential materials for generation of coherent UV light in solid state lasers. KBBF is the only material that can achieve coherent light below 200 nm by direct second harmonic generation (SHG). However, its strong layer habits and the high toxicity of the beryllium oxide powders required for synthesis limit its application. By substituting Be with Zn and connecting adjacent [Zn2BO3O2] ∞ layers by B3O6 groups, a new UV nonlinear optical material, Cs3Zn6B9O 21, was synthesized. It overcomes the processing limitations of KBBF and exhibits the largest SHG response in the KBBF family.

Cs3Zn6B9O21: A Chemically Benign Member of the KBBF Family Exhibiting the Largest Second Harmonic Generation Response

Mid-IR nonlinear optical (NLO) materials are of great importance in modern laser frequency conversion technology and optical parametric oscillator processes. However, the commercially available IR NLO crystals (e.g., AgGaQ2 (Q = S, Se) and ZnGeP2) suffer from two obstacles, low laser damage thresholds (LDTs) and the difficulty of obtaining high-quality crystals, both of which seriously hinder their applications. The introduction of Cl, an element with a large electronegativity, and Pb, a relatively heavy element to promote the optical properties, affords an oxide-based IR NLO material, Pb17O8Cl18 (POC). High-quality POC single crystals with sizes of up to 7 mm × 2 mm × 2 mm have been grown in an open system. Additionally, POC exhibits a large LDT of 408 MW/cm2, 12.8 times that of AgGaS2. POC also exhibits an excellent second harmonic generation response: 2 times that of AgGaS2, the benchmark IR NLO crystal at 2090 nm, and 4 times that of KDP, the standard UV NLO crystal at 1064 nm. Thus, we believe that P...

Pb17O8Cl18: A Promising IR Nonlinear Optical Material with Large Laser Damage Threshold Synthesized in an Open System

High pulse energies of nanosecond-level fourth- and fifth-harmonic (4omega and 5omega) generation of a Nd:YAG laser have been obtained with a CsLiB(6)O(10) (CLBO) nonlinear crystal. 500 mJ of 4omega output with a conversion efficiency of 50% from the second-harmonic input was generated. 5omega output at 213 nm of as high as 230 mJ was obtained by sum-frequency generation of the 266- and 1064-nm beams, corresponding to a 10.4% conversion efficiency of the initial fundamental input energy. The characteristics of the CLBO crystal that permit this effective frequency conversion are discussed.

Takatomo Sasaki

Papers

High-power fourth- and fifth-harmonic generation of a Nd:YAG laser by means of a CsLiB 6 O 10