We then present the results of the pure absorptive 2D spectra for the monomer coupling to the cavity when varying cavity loss rates and light-matter coupling strengths. In the off-diagonal peaks (cross peaks) of the polariton 2D spectra, we observe the coherent energy exchange between the upper and lower polariton states, with the frequency corresponding to the Rabi splitting. Further, the cavity loss acts as a homogeneous broadening (width along the anti-diagonal direction of the diagonal peaks in Fig. ) that dampens the polaritonic energy transfer and signal intensities. The increase in light-matter coupling strength causes a larger splitting of polaritonic peaks. Finally, we present the 2D spectra of an exciton dimer coupled to a cavity. We present the total signal for the 2D spectra as well as individual contributions from different Liouville pathways, including ground state bleaching (GSB), stimulated emission (SE), and excited state absorption (ES), for both rephasing and non-rephasing pathways. These pathways are then interpreted from how different polariton eigenstates contribute to each of the signals on the basis of the dipole matrix in the polariton eigenbasis.