Thermal stresses and end-bulging in the laser disc from a tetragonal [1 0 0]-cut crystal

Abstract

The problem of thermal stresses and strains is considered in relation to the laser disc from a tetragonal crystal cut along [1 0 0] axis under plane stress approximation (for diode-pumped lasers). The formula describing the contribution of end-bulging of the disc to the optical power of the thermal lens is obtained. It is shown that end-bulging for anisotropic crystal is partially responsible for the astigmatism of the thermal lens. The relationship between the anisotropy of thermal expansion and the position of the principal meridional planes of the thermal lens is shown. Thermal stresses, strains and displacements, as well as the end-bulging term of the 'generalized' thermo-optic coefficient are calculated for a disc from an a-cut yttrium vanadate, Nd:YVO 4 . The stress fracture issues for this crystal are also analyzed.

Power scaling of single-longitudinal-mode Nd:GdVO4laser at 1342 nm

“…The lower threshold pump power, the higher output power, and the higher thermal fracture limit pump power for a composite Nd:GdVO 4 laser medium than that for a conventional Nd:GdVO 4 laser medium, confirms the fact that the laser performance can be improved by using a composite laser medium, and it also proves the validity of the theoretical analysis on the influence of cross dimensions of a laser medium on the thermally induced diffraction losses and thermal fracture limit pump power in part 2. A recent investigation [28] has shown that the thermal stresses are proportional to the radius of laser medium. It means that thermal fracture limit pump power P abs lim is the decreasing function of the radius of laser medium since the thermal stresses are also proportional to the pump power, and the maximum pump power (fracture limit) is a constant.…”

Thermal stresses and end-bulging in the laser disc from a tetragonal crystal: the case of LiYF4

“…Indeed, S′ 15 = −S 16 and S′ 35 = S 16 components are non-zero, equation (3b). It should be noted that for yttrium vanadate crystal, YVO 4 , S 16 = 0 so the plane of elastic symmetry exists for both a-cut and c-cut discs and, hence, all shear stresses are zero, as described in [18]. The angular dependence of τ zθ and τ rz stresses for 1 mm-thin Tm:LiYF 4 disc and P abs = 1 W are shown in figure 3 for various radial coordinates, exhibiting either positive or negative values.…”

“…The only report on a close topic is Sirotin's paper [16] which presents analytical expressions for stresses in a heated rod from any anisotropic crystal (including the case of tetragonal crystal like LiYF 4 ). Very recently, we performed the analytical analysis of the thermal stress-strain problem and end-bulging for tetragonal yttrium vanadate, YVO 4 [17,18]. However, the obtained solution cannot be applied to LiYF 4 .…”

Photo-elastic effect, thermal lensing and depolarization ina-cut tetragonal laser crystals

“…Here, α is the thermal expansion coefficient in the direction of light propagation, α is its mean value in the disc plane, α = (α a + α c )/2, n is the refractive index of an unpumped ('cold') crystal, Q A(B) are the so-called photo-elastic constants. Parameter ν * indicates the contribution of end-bulging effect that occurs due to the thermal stresses (in contrast to the part that originates solely from the thermal expansion) [21].…”