Lithium triborate

Only certain types of crystalline materials can exhibit second harmonic generation (61). Because of symmetry considerations, the coefficient must be identically equal to zero in any material having a center of symmetry. Thus the only candidates for second harmonic generation are materials that lack a center of symmetry. Some common materials which are used in nonlinear optics include barium sodium niobate [12323-03-4] Ba2NaNb O lithium niobate [12031 -63-9] LiNbO potassium titanyl phosphate [12690-20-9], KTiOPO beta-barium borate [13701 -59-2], p-BaB204 and lithium triborate... 

The Opal uses a temperature-tuned, 90 phase-matched lithium triborate (LBO) crystal as its nonlinear gain medium (see Fig. 2.11). It is pumped at either 775 nm or 810 nm with an average power of 2 W at a repetition rate of 82 MHz the pump pulse width amounts 80 fs. The Opal produces two output wavelengths, the main resonated signal output and a less powerful (p 50%) idler output. Table 2.1 summarizes the performance obtained. 

The IR and Raman spectra of lithium triborate glasses doped with Nb205 contained characteristic features of NbOe units. The IR spectra of oxide materials (Mn,Fe)(Nb,Ta)206 gave assignments to Nb/Ta-Oe and Fe/Mn-Oe octa-hedra. Raman spectroscopy was used to monitor the M (= Nb or Ta) environments in phosphoniobate and -tantalate glasses doped with iron. ... 

The so-called metaborates of empirical formula B02 can take several forms. The infinite linear (B02) T ion is found in the low-temperature form of LiB02 (449), Ca(B02)2 (275), and Sr(B02)2 (46). At high temperatures and pressures, the lithium compound possesses a sphaleritelike structure with boron in four-coordination (278). The triborate isolated B3Or group is found in the barium (297), sodium (276), and potassium (361) compounds, and the framework B30 " group, in which all the boron atoms are tetrahedral, exists for a high-pressure calcium metaborate phase (280) and copper metaborate (284). Two other anhydrous calcium metaborates are known to give the series... 

In order to test this hypothesis and determine an appropriate structural model for solution-deriyed lithium borate networks (gels), Brinker et al. performed FTIR investigations of crystalline alkali borates and partially hydrated crystalline alkali-borates (with N4 = 0.25 to 0.50). A prominent spectral feature (see, e.g.. Fig. 37a) of the anhydrous tetra- and triborate compounds is the 1260-cm vibration due to oxygens bridging between trigonal borons contained in separate primary units [183] (Fig. 38a). Anhydrous lithium diborate is composed exclusively of diborate units linked by oxygens bridging between 3- and 4-coordinated borons and exhibits no 1260-cm vibration [185]. Partial hydrolysis of the tetra- (and triborates) causes a dramatic reduction in the relative intensity of the 1260-cm vibration (Fig. 37b). 

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