By considering selected examples of new structure types, guidelines are set forth for the synthesis of new solid-state inorganic borates that are likely to have desirable properties for nonlinear optical applications. The structures of two new, noncentrosymmetric orthoborate fluorides BaCaBO3F and Ba7(BO3)3F5 demonstrate a feasibility for controlling linear optical properties and for producing noncentrosymmetric borates that melt congruently. The structure of SrLi(B3O5)3 represents an additional example of a noncentrosymmetric borate resulting from chirality of the B3O7 ring. In addition to potential practical value, crystals of the type AMOB2O5 (A = K, Rb, and Cs; M = Nb and Ta) provide a unique means for examining the structural dependent interrelationships of linear and nonlinear optical properties.
A porous, luminescent surface is produced on n‐Si by irradiation in anhydrous or aqueous hydrogen fluoride without an externally applied potential. The photoluminescence spectra of the resulting surfaces are similar to those obtained by the anodization method. A porous surface is only produced when electrical contact is made between the n‐Si disk and a metal surface such as Au or Hg, and, in the aqueous system, when dissolved
O2
is present.
Spectroscopic and laser properties have been characterized for Nd 3ϩ in LaSc 3 ͑BO 3 ͒ 4 . The Judd-Ofelt analysis has been applied to the measured room temperature absorption spectrum to determine the radiative decay rates and branching ratios of Nd 3ϩ transitions from the 4 F 3/2 metastable state to the 4 I J lower-lying manifolds. The parameters ⍀ 2 , ⍀ 4 , and ⍀ 6 are larger than those reported for Nd 3ϩ in other laser host crystals. The value of ⍀ 4 /⍀ 6 is approximately 3.0 times larger than that of Nd 3ϩ in yttrium-aluminum-garnet ͑YAG͒ and about 1.4 times larger than that of Nd 3ϩ in the  phase of LaSc 3 ͑BO 3 ͒ reported recently. The measured room temperature fluorescence lifetime of the 4 F 3/2 → 4 I 11/2 transition is 150 s, while the Judd-Ofelt analysis predicts a radiative lifetime for the 4 F 3/2 state to be 249 s, resulting in the fluorescence quantum efficiency of 60%. The emission cross sections of the 4 F 3/2 → 4 I 11/2 and 4 F 3/2 → 4 I 13/2 intermanifold transitions have been also determined at room temperature. Finally, these results are compared with those of the standard laser material Nd 3ϩ :YAG.
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