Katsuki-san, Marc

Today we removed the AZTEC sample in order to prepare the absorption and birefringence measurement of the TAMA T1 sample.

We reinstalled the steering mirror in the injection part to dump the sample reflection (see fig1)

We installed a flipping mirror before the birefringence readout to redirect the pump beam to the high power power meter (see fig2).

We reconnected the absorption photodiode to the lockin amplifier.

We installed the surface reference sample and with z = 42.3mm and zIU = 66 mm we got R_surf = 18.72 /W

We installed the bulk reference sample with z = 40.95 mm  and zIU = 65.7 mm and got R_bulk = 0.6679 cm/W.

We installed the TAMA T1 and using DC values could find Y_center = 121.92 mm and X_center = 326.74 mm.

We increased the pump laser current to 6A (beforehand we changed the HWP angle that control the power to 9 deg that corresponds to the min pump power) which gave Pt ~6.1W.

We realigned the DC at the previous z_center (62.4mm) and did long z scan but could not find clear surfaces absorption neither on the AC nor the phase.

This seems to confirm that this sample absorption is quite low ( previously measured at 18 ppm).

Because it is the first time using such high power with all the birefringence optical component we turned off the laser today and will start the absorption measurement tomorrow morning.