Cs₂GeB₄O₉: a New Second-Order Nonlinear-Optical Crystal

Abstract

A new alkali-metal borogermanate with noncentrosymmetric structure, namely, Cs2GeB4O9, has been discovered, and a large crystal with dimensions of 20 × 16 × 8 mm(3) has been grown by a high-temperature top-seeded solution method using Cs2O-B2O3 as a flux. The compound crystallizes in the tetragonal space group I4 with a = b = 6.8063(2) Å, c = 9.9523(7) Å, V = 461.05(4) Å(3), and Z = 2. It features a three-dimensional anionic open framework based on GeO4 tetrahedra and B4O9 clusters that are interconnected via corner-sharing, forming one-dimensional channels of nine-/ten-membered rings along the a and b axes, which are occupied by Cs(+) cations. Cs2GeB4O9 exhibits a very high thermal stability with a melting point of 849 °C, and it possesses a short-wavelength absorption edge onset at 198 nm determined by UV-vis transmission spectroscopy measurements on a slab of polished crystal. Powder second-harmonic generation (SHG) measurement on sieved crystals reveals that Cs2GeB4O9 is a type I phase-matchable material with a strong SHG response of about 2.8 × KH2PO4. The preliminary investigation indicates that Cs2GeB4O9 is a new promising second-order nonlinear-optical crystalline material.

Synthesis, Crystal Structure, and Nonlinear Optical Properties of a New Alkali and Alkaline Earth Metal Carbonate RbNa5Ca5(CO3)8

“…UV nonlinear optical (NLO) crystals [1][2][3][4][5][6][7][8] have attracted widespread attention owing to their significant roles in laser science and related technology. Although several crystals with excellent nonlinear optical properties are well known, such as β-BaB 2 O 4 [9], LiB 3 O 5 [10] and CsB 3 O 5 [11], and part of which have been commercially manufactured and used worldwide, the design and synthesis of new NLO materials with large macroscopic nonlinearities and wide transparency ranges are still a particularly difficult challenge.…”

“…Similarly, the same planar triangular [CO 3 ] 2-groups are considered to be excellent NLO-active anionic groups as well. Recently, many excellent UV and deep-UV carbonate NLO crystals have been synthesized, such as ABCO 3 F (A = K, Rb, Cs; B = Ca, Sr, Ba) [19], APbCO 3 F(A = Rb, Cs) [20,21], K 2.70 Pb 5.15 (CO 3 ) 5 F 3 [22], Na 8 Lu 2 (CO 3 ) 6 F 2 [23], Na 3 Lu(CO 3 ) 2 F 2 [23], Na 4 La 2 (CO 3 ) 5 [24], CsNa 5 Ca 5 (CO 3 ) 8 [24], and Na 3 Re(CO 3 ) 3 (Re=Y, Gd) [25]. Lately Lin's group confirmed that [CO 3 ] 2-groups have a distinct advantage in birefringence and SHG effects in NLO crystals by theory calculation in comparison with [BO 3 ] 3-group [26].…”

Laser operated optical features in β-BaTeMo2O9:Cr3+ nanocrystallites

“…Most of inorganic oxide nonlinear optical crystals are characterized by stable output second order susceptibilities [1,2], which usually possess fixed parameters, and therefore cannot be operated by means of external fields (dc electrical, optical or acoustical one). However, in many applications of nonlinear optics and quantum electronics it is necessary to perform operations by these parameters [3,4].…”

Recent advances on second-order NLO materials based on metal iodates

“…As for the metal-oxide-based system, two important types of inorganic asymmetric units favor NLO activity: trigonal planar (BO 3 ) 3− with a -conjugated system [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], and cations subject to second-order Jahn-Teller (SOJT) distorted cations such as octahedrally coordinated d 0 transition metal (TM) cations (e.g. Nb 5+ , V 5+ , Mo 6+ ) and lone-pair cations (Se 4+ , Te 4+ , Pb 2+ , Bi 3+ , etc.)…”

“…During the last ten years the explorations of new borate-based NLO crystals for the use in UV and deep-UV regions have greatly expanded the borate family to include beryllium-borates [21][22][23], borosilicates [24], borogermanates [26,27], galloborates [28], borosulfates [29,30], etc. In the meantime several new metal phosphates with good SHG properties have been also discovered [40,41].…”