Laser irradiation and scanning were carried out by a lab-built confocal Raman system, which consists of a 532 nm continuous laser source with a maximum power of 55 mW and a Zaber ASR-E closed-loop microscope stage (Zaber Technologies Inc., Canada) for scanning and focusing control. An Olympus (MPLFLN50X) objective lens (50×, NA = 0.50) with ~0.7 μm beam spot size was used to scan over the samples' surface, and the optical shutter of the spectrometer controlled the exposure time. Assuming the Gaussian beam profile, the calculated 1/e 2 diameter of the focused laser beam was 0.61 μm using the optical parameters in the setup (λ = 532 nm, M 2 = 1, focal length of the objective = 3.6 mm, beam diameter at lens = 4 mm). However, experimentally, the beam profile was a tad asymmetrical, and the beam spot size of ~ 0.7 μm was measured from the SEM image of the individual melted TiO2 matrix due to plasmonic heating.