4-methyl umbelliferone compound is synthesized from resorcinol with ethyl acetoacetate under ultrasound irradiation as an assistant of reaction. The coumarin derivative, COM-ester compound, is synthesized from the 4-methyl umbelliferone with chloroethyl acetate also using ultrasound irradiation. The COM-ester compound is characterized via spectroscopic, FTIR and 1H NMR methods. The geometrical optimization and thermodynamic characterization of the COM-ester compound are theoretically investigated via DFT. To determine the HOMO, LUMO, Mullikan atom charges and electronic spectrum of the investigated COM-ester compound, the hybrid functional B3LYP and CAM- B3LYP procedures are applied. Nonlinear optical (NLO) properties of the COM-ester compound are studied via the diffraction patterns (DPs) and Z-scan techniques where it's nonlinear refractive index (NLRI), n2, is obtained using cw, low power laser beam. As high as 4.658 × 10−11 m2/W of n2 is obtained. The all-optical switching (AOS) of the COM-ester compound is tested using two 473 and 532 nm cw, visible laser beams, both static AOS and dynamic AOS.