Figure 7.
Slope measurements of an active grating with an in-position LTP. (a) The measured grating slope and its target polynomial slope function y t′(x) = c 1 x + 2c 2 x + 3c 3 x 2 + 4c 4 x 3, in which c 1 = 1.95 × 10−5, c 2 = 9.08 × 10−6, c 3 = −3.85 × 10−9 and c 4 = 5.94 × 10−14. The function y t′(x) is vertically offset for clarity. (b) The difference between the measured and target slope functions. The r.m.s. of this difference is 0.23 µrad. (c) The profile function of the grating surface obtained from the integration of the measured slope, with the height at the grating centre defined as zero.