Numerical modeling of a four-rod pumping scheme for improving TEM ₀₀ -mode solar laser performance

A four-rod solar pumping concept is proposed for the significant improvement in TEM ₀₀ -mode solar laser performance. A quadrangular pyramidal reflector is used to separate the focused solar rays from a 2.0-m diameter parabolic mirror into four focal spots. Four laser heads, each one consisting of a double-stage biconical lens/conical pump cavity and a small diameter Nd:YAG rod, are placed at each of the four focal zones. TEM ₀₀ -mode laser output of 7.22 W is numerically obtained from each rod, resulting in 28.9 W(4 × 7.22 W) total TEM ₀₀ -mode power from the four-rod scheme with 9.41 W/m ² collection efficiency. This value is 2.5 times more than that of the numerically calculated laser power collection efficiency from a single-rod pumped by the same parabolic mirror. A brightness conversion efficiency of 0.86% is achieved. Substantial improvements in TEM ₀₀ -mode solar laser stability and thermal performance are also numerically demonstrated.