interaction that 2D materials have demonstrated has made them highly attractive for practical device applications. Graphene, the archetype 2D material was explored extensively for a wide array of photonic applications 1 . However, due to the lack of direct bandgap in graphene, considerable attention has shifted towards 2D materials known as layered transition metal dichalcogenides (TMDs) 2,3 . These TMDs are a group of naturally abundant material with a MX 2 stoichiometry, where M is a transition metal element from group VI (M = Mo, W); and X is a chalcogen (M = S, Se, Te). One of the most intriguing aspect of TMDs is the emergence of fundamentally distinct electronic and optoelectronic properties as the material transitions from bulk to the 2D limit (monolayer) [4][5][6][7][8] . For example, the TMDs evolve from indirect to direct bandgap semiconductors spanning the energy range of 1.1 to 1.9 eV in the 2D limit 4-6 .Among the TMDs, molybdenum disulphide (MoS 2 ) is one of the most widely studied systems used to demonstrate 2D light emitters 9 , transistors 10,11 , valleytronics 12-15 and photodetectors 16,17 . The novel excitonic properties of 2D MoS 2 that make it very interesting for both fundamental studies and applications include: (i) the enhanced direct band gap photoluminescence (PL) quantum yield of the monolayer compared with the bulk counterpart 7,8 , (ii) the small effective exciton Bohr radius (0.93 nm) and associated large exciton binding energy (0.897 eV) 18,19 providing the opportunity for excitonic devices that operate at room temperature (RT) and (iii) the 2D nature of the dipole orientation making the excitonic emission highly anisotropic 20 . 3The interaction of a dipole with light can be modified by altering the surrounding dielectric environment. The most widely studied and technologically relevant phenomenon in this context is the Purcell enhancement wherein the spontaneous emission rate of the dipole is enhanced using an optical cavity by altering the photon density of states. Here the coupling between the dipole and the cavity photon is defined to be in the weak coupling regime since the interaction strength is weaker than the dissipation rates of the dipole and the photon. This regime has been demonstrated in the 2D materials using photonic crystal cavities coupled to 2D layers of MoS 2 21 , and WSe 2 22 . It resulted in an enhancement of the spontaneous emission rate and highly directional photon emission.When the interaction between the dipole and the cavity photons occur at a rate that is faster than the average dissipation rates of the cavity photon and dipole, one enters the strong coupling regime resulting in the formation of new eigenstates that are half-light -half-matter bosonic quasiparticles called cavity polaritons. Since with the pioneering work of Weisbuch et al. 23 there have been numerous demonstrations of cavity polariton formation and associated exotic phenomena in solid state systems using microcavities and quantum wells that support quasi 2D excitons [24][25][26] . H...

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