Figure 28

Figure 28: Thermal lensing from a ring radiator. Red dashed curve: nearest paraboloid (weighted by the readout beam intensity). The readout beam is TEM00 with w = 2 cm. The curvature is weakly dependent on the beam width: 87 km W for w = 2 cm, 95 km W for w = 6.65 cm. Green dashed curve: Zernike expansion of the lens