Identification of Whispering Gallery Mode (WGM) coupled photoluminescence and Raman modes in complex spectra of MoS2 in Polymethyl methacrylate (PMMA) microspheres

A ripples structure is observed in the photoluminescence (PL) spectra of MoS2 adsorbed on the surface of single polymethyl methacrylate (PMMA) microspheres in contrast to the broad spectra of nanosheets. Theoretical simulations and photonic nanojet technique have been used to identify the ripple structures. Part of these structures has been found to be due to the whispering gallery modes (WGMs) of the microcavity. The Raman modes of MoS2 and PMMA, on the other hand, are identified by the photonic nanojet induced enhancement. This work helps applications in photonics and sensing technique which require clean systems with well characterized spectral lines.