Quantitative pump-induced wavefront distortions in laser-diode- andflashlamp-pumped Nd:YLF laser rods

摘要

Detailed interferometric measurements of the induced thermalndistortions due to laser-diode and xenon flashlamp pumping of Nd:LiYFn4 are presented. The thermal distortions are quantified innterms of the primary aberrations of defocus, astigmatism, coma, andnspherical. Defocus and astigmatism are shown to dominate the thermalnaberrations. The measured defocus and astigmatism are converted to thenconventional thermal-focal lengths in two perpendicular directions withnrespect to the Nd:YLF crystalline c axis for each of the twonpolarization states Σ and Π. A comparison of the thermal-focalnlengths measured with our xenon flashlamp and laser-diode-pumped rods isngiven when the rods are pumped to the same small signal gain. Wencalculate effective dioptric-power coefficients from our data forncomparison to those reported in the literature for krypton-flashlampnpumping. A thermal time constant of 1.5 s is measured for ournlaser-diode-pumped Nd:YLF laser rod