INDEX electroluminescence

The parameters that are measured run a wide gamut from the routine (current, potential or some electrical parameter) to the exotic (e.g., beam deflection due to refractive index changes). A hierarchical approach to discussing these variant methods has been described [52]. Thus, the methods in Table 2 fall under the categories of purely electrical (entries 1-3, 8 and 9), purely optical (entry titled photoluminescence spectroscopy and entries 12 and 13), electro-optic (electroluminescence spectroscopy) or opto-electric (entries 4-7). We can also distinguish between frequency-resolved (entries 3-7) and time-resolved (entries 10 and 14) measurements, although it must be noted that in many instances (e.g., entries 8 and 11) both steady-state and time-resolved approaches are feasible. 

FIGURE 4.5. Electroluminescence spectra from three devices which have different optical thicknesses. The presence of a second mode in one of the spectra is a result of a closer than ideal mode spacing, If the refractive index difference between the materials that constitute the QWS is enhanced, the total optical thickness will be reduced and the mode spacing increased. 

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