You can use it for an approximate estimation of the possible content of triangles with one non-bridging oxygen atom in your glass if you consider the total content of Na2O, ZnO and TiO2 as that equal to the content of Na2O because, being an acidic oxide, B2O3 tends to mainly interact with more alkaline oxide, Na2O. Figure 5.6 shows the results of calculation of the content of basic structural units present in sodium borate glasses.
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It is based on information on the Gibbs free energies of formation of crystalline compounds existing in a given system together with information about their structure. A description of the theoretical approach for calculating the fractions of basic structural units is given in Sectons 5.3 and 5.4. You will find a detailed answer to your question in the attached file. However, the advent of thin film LN has addressed this issue. This leads to an ultimate limit in its conversion efficiency or requires huge voltages in modulator. Another limiting factor of LN are the huge mode sizes in indiffused waveguides in bulk samples. It takes more power This is also one of the reasone, why still alternatives are researched, such as KTP). Just search for research directed to address LNs photorefraction (which I think is also one field, where BBO comes in. But again, LN is not without its problems. LN is relatively resistant to scratches, it melts only a way above 1000☌ etc.
Even domain structures stay stable for years. In contrast to this, LN as a crystal stays stable for years. Large molecules tend to decompose or change their chemical structure under UV light, heat or ambient chemical enviromements. But polymers have one big issue, which is stability. People have built extremely efficient nonlinear frequency converters or electro-optic modulators out of this. By the way, you may now ask, we we are not using nonlinear polymers. If you just compare the nonlinear coefficients of these molecules with LN, you will find 100 or 1000 times higher nonlinearities easily. However, why is the B1g mode at 235 cm-1 suppressed in the excited spectrum? Is such a significant shift (to 259 cm-1) of the B1g mode possible?Ĭan you help me with the interpretation? Or do you know anybody who can help me here? The Raman band at 198 cm-1 comprise three components: 188, 198.6, and 215 cm-1. I assume that this mineral is stishovite with extreme intense bands at 198 and 753 cm-1.
However, such minerals do not exist in this paragenesis. Only some simple borates have such a band around 753 cm-1. The band at 259 cm-1is genuine and not a spike. Later the stimulated intensity of this phase decays too. Stishovite is at room-conditions metastable. Repetition was not possible because the phase also transformed after measurement into stimulated spectra of tridymite and quartz. The background intensity (basis line) for the “stimulated” spectrum corresponds to the strongest garnet band intensity at 915 cm-1 of the matrix mineral almandine.
I call this spectrum “stimulated” because the Raman spectrum with three extremely intense and sharp bands at 198, 258, and 753 cm-1 differ from the matrix spectrum by a factor of five. From a tiny crystal (about 2µm in diameter) inside a melt inclusion, I obtained a Raman spectrum with extraordinary high intensities. During my Raman work on melt inclusions in almandine from the granulite facies prismatine rock from Waldheim/Saxony, I observed an unusual metastable Raman spectrum.
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