Study on laser intensity modulation by spherical inclusion in silica subsurface

Abstract

A three-dimensional model of the field in the vicinity of a spherical inclusion in fused silica illuminated by a laser beam is established based on Mie scattering theory, and intensity distributions of the scattered field modulated by the inclusion are studied. The effects of refractive index and the radius of inclusion on light intensity enhancement factor (LIEF) and the position of the maximum intensity are analyzed. The results show that modulation effect of inclusion can be considered ineffective when inclusion radius is below 40 nm. When the radius is above 40 nm, inclusions (voids, Al, Fe, ZrO 2 ) act as positive or negative lenses for the incident laser. Maximum light intensity is two orders of magnitude larger than the incident wave intensity in some parts distance away from inclusion. For a non-dissipative inclusion, maximum LIEF increases with the increasing difference between refractive index of inclusion and fused silicon. With the increasing of refractive index, the point of the maximum intensity moves from the backward to the forward of the inclusion. For a dissipative inclusion, with the increasing of the imaginary part of the refractive index, real part of the refractive index has less effect on LIEF. LIEF increases with increasing radius, and the points of maximum intensity move from the forward to the backward of the inclusion.

Optically Induced Structural Instability in Gold–Silica Nanostructures: A Case Study

“…This implies that the rate of heat transfers to the surrounding medium and the resultant vapor bubble formation becomes the primary source for PA signal generation, and hence, for a coated nanostructure, it depends mainly on the shell thickness. − However, in such nanosystems, the PA signal generated can be evaluated to be about a few pascals to kilopascals whose magnitude negligibly affects the structural stability of the system. In the current investigation, the possibility of supplementary phenomena such as surface evaporation and light intensity modulation effect is eliminated because of silica coating on Au cored nanostructure (≤40 nm) . Therefore, under normal conditions, a primary source of pressure generation can always be assigned to the thermal expansion of nanostructure.…”

“…In the current investigation, the possibility of supplementary phenomena such as surface evaporation and light intensity modulation effect is eliminated because of silica coating on Au cored nanostructure (≤40 nm). 26 Therefore, under normal conditions, a primary source of pressure generation can always be assigned to the thermal expansion of nanostructure.…”

Modeling and analysis of post plasmonic effects in optically excited metal nanosystems

“…An eventual strong enhancement of the electromagnetic field in interference points resulting in damage of silica lattice pattern. However, considering the case of nano sized AuNP (radius < 40nm), the effect of this field intensity modulation is insignificant [95]. ticle by evaporation due to heat deposition on the lattice but this occurs only near boiling point of the nanoparticle.…”

“…Additionally, the effect of presence of crack was studied stating that pre-existing cracks in silica can amplify the damage effect by either trapping the nano-inclusions or by field amplification [93]. A study on intensity modulation by spherical inclusions shows that intensity enhancement by particles greater than 40 nm is significant [95]. However, these studies use direct fluence in the range of 4 J/cm 2 and above or intensity in the corresponding range for nanosecond pulsed irradiation.…”