Investigation of optical phonon modes and figure of merit of graphene oxide nanosheets for use in optical switching devices

X-ray diffraction pattern (XRD), Transmission electron microscope (TEM), Raman spectroscopy and Fourier transform infrared (FTIR) are used to characterize the structure of graphene oxide nanosheets. The results show the presence of thin graphene oxide layers, which have a suitable crystal structure with a peak of about 10 degrees and a ratio of ID/IG about 0.99. Also, by employing Kramers-Kronig (KK) relations and obtaining their refractive index, extinction coefficient and dielectric function via FTIR spectroscopy, the optical phonon modes, the transverse optical phonon (TO) and the longitudinal optical phonon (LO), of this material have been calculated. Then, the nonlinear optical (NLO) properties were obtained through the single-beam Z-scan method using a continuous wave (CW) Nd:YAG laser with a wavelength of 532 nm. The Z-scan results show that graphene oxide nanosheets have the phenomena of self-focusing and two photon absorption (TPA). In addition, a suitable figure of merit (FOM) was obtained for these nanosheets.