Thermal lensing in high-power diode-pumped Yb:KGW laser

Abstract

We investigated thermal-lensing effects in a diode end-pumped Yb:KGW laser with slab shaped active element. Performance and thermal lensing properties for Ng cut Yb:KGW and Yb:KGW cut for athermal propagation direction are presented. It is found that crystal cut along athermal direction provides weaker thermal lens than Ng cut active element, however, due to anisotropic Yb:KGW characteristics, thermal lens is highly astigmatic. End bulging contribution to thermal lensing under intense pump was measured (for Ng cut active element).

A continuous wave Yb:KGW laser with polarization-independent pump absorption

“…In this case, the negative thermo-optical coefficient dn/dT plays a dominant role in the formation of the thermal lens, and to some extent this is balanced by the positive effect of thermal expansion. This is in sharp contrast to the previously reported positive values of thermal lenses in [12,13] where the positive effect of thermal expansion took a dominant place over the negative thermo-optical effect (e.g. in N p -cut crystals), or both the thermal expansion effect and the thermo-optical effect had positive values (e.g.…”

Application of Yb:KGd(WO4)2crystals to lasers with high brightness beams

“…where ν is the Poisson ratio, k is the thermal conductivity, σ T is maximal tension that the material can resist, α is the thermal expansion coefficient, and E is the Young's modulus. Thus, for example, a Yb:KGW slab with thickness of 1 mm can stand pump power up to 100 W without thermal stress failure [17,18]. Gradients of temperature and stress result in an aberrational thermal lens long before thermal breakdown of laser material [15,16,19].…”

Efficient high-power orthogonal dual-slab Yb:KGd(WO4)2 laser oscillator with TEM00 mode

“…D. Stucinskas. et al obtained a CW output power of 17 W with Ng-cut Yb:KGW crystals and 8.5 W with athermal cut Yb:KGW crystal [22]. The diode-pumped single crystal and dual-crystal Yb:KGW lasers were reported by G. Kim et al.…”

“…D. Stucinskas et al studied the thermal lensing in Ng-Yb:KGW crystals by wavefront detector. Under the lasing condition, the thermal lens focal power of the two axes differed widely, leading to severe astigmatism with the elliptical beam profile [22]. P.A.…”