Process Engineering of Dimensional Fused Silica Etching

The process of dimensional fused silica etching was offered. The production process of molycoat by magnetron sputtering of molybdenum target in inert gas (Argon) on vacuum distillation unit (NIKA-2012 TN) was examined. The coat quality (delamination, discontinuity) was analyzed; the influence of the first kind internal strains on the type of the observed defects was determined. The research was conducted by means of microscopic and X-ray diffraction analysis. It has been established that the internal strain value in the coat depends on the sputtering gas (Argon) flow rate, and, consequently, its pressure in the magnetron system for molybdenum sputtering. Zero stresses are registered under Argon's flow rate, which is 7.5 L/h. Influence of internal stresses level in the barrier coating on the quality of etching dimple.

On the use of photoelastic effect and plane strain or plane stress approximations for the description of thermal lensing

Correct use of the photoelastic effect for the description of thermally induced refractive index change is discussed and the analytical relations between thermo-optic coefficients at zero stresses and zero strains are found for all classes of cubic crystals. These relations may be useful for the investigation of thermal effects in very promising sesquioxide class m3 laser crystals. An accepted set of elasto-optical coefficients of the YAG crystal and an alternative one found in the literature were used in numerical simulations. Significant differences in the calculated thermo-optic coefficients and induced birefringence are found using different sets of these coefficients. Misunderstandings related with the so-called photoelastic coefficients are resolved and new expressions for these coefficients are found. It is shown that the incorrect use of these coefficients for different pump beam distributions can lead to significant discrepancies for thermally induced birefringence. It is also shown that common use of the generalized thermo-optic coefficients significantly overestimates the values of optical power of thermal lenses when they are applied to the laser rods with lengths several times longer than their diameter.

Effect of Stress-Free Edges in Plane Shear of a Rectangular Orthotropic Region

The plane elastic problem of a rectangular orthotropic region is considered; subject to the boundary conditions of prescribed equal and opposite tangential displacements and zero normal displacements on the upper and lower edges and zero stresses on the remaining edges. The effect of the stress-free edges on the stiffness coefficient relating the tangential displacement and the corresponding shearing force is estimated in the form of upper and lower bounds for this coefficient.

Approximate Stress Functions for Triangular Wedges

The variational method is used to determine expressions for approximate stress functions for determining the effect of a third boundary to an infinite triangular wedge. The approximate function is a solution of a Euler-Lagrange total differential equation of the variational calculus with the constants of integration determined from the condition of least work. The approximate function yields zero stresses on the sloping faces of the wedge but furnishes correction stresses on the third boundary.