On the other hand, one should be careful because these coupling parameters do not include the magnitude of the dipole, either µ αα (R) or µ αβ (R), and both values could vary significantly by changing R for a given system. These values also need to be included when judging if a system is under a particular coupling strength. Further, it should be noted that for Fabry-Pérot cavities, the area of the mirrors is typically considered constant when comparing different frequencies. In this case, the cavity volume is inversely proportional to cavity frequency, and A 0 would be independent of frequency, while λ would be frequency-dependent. For the majority of this review, these two parameters are used to represent coupling strength.