Mode coupling in light scattering spectrum results in the shifts of characteristic frequencies of uncoupled bare excitations, various interference effects, and line shape anomalies. Therefore, it is necessary to analyze the Raman spectrum from coupled modes by means of the appropriate line shape function in which the coupling effect is considered.
We discussed the significance and the indeterminancy of two coupled Damped Harmonic Oscillator (DHO) model which is generally used in analysis of the Raman spectrum from linearly coupled modes. Also, we discussed how the spectra are formed when Fermi Resonance and Fano Resonance occur in solids.
