Marc Matteo

This entry summarizes these past days activities.

We found a mistake in the fitting code (the wavelength was hard coded to 633 nm instead of 1064 nm making the previous estimation wrong by a factor sqrt(1064/633))

To avoid this issue, we coded a more flexible function 'fit_blade.m' that is saved in the PCI scripts folder on the desktop

With this function, we could finally tuned the pump beam telescope and recover Manuel's parameters (fig 1)

We also check the vertical and horizontal angle of incidence to be -0.2 deg and 2.5 deg respectively.

We also checked the probe beam parameters by placing a power meter in front of the absorption PD.

We also got same parameters as Manuel (fig 2)

The angle of incidence is 3.47 deg meaning that the relative angle between the probe and pump beam is also correct.

We installed the surface reference sample and tried to maximize the R coefficient by changing both the translation stage and imaging unit z positions.

While doing these motions, we could find the expected maximum at x = 35 mm and z_iu = 68 mm.

However, R = 14 /W meaning that we still had not optimal conditions.

After investigating other possible issues (chopper frequency, laser power, pd, lock-in are all fine) and repeating several times this calibration, we could not improved this value by much...

We installed the bulk reference sample and got R = 0.5536 cm/W.

Both surface and bulk calibration are 10 % lower than expected but the reason is still not clear to us...

We decided to use the 1.5 inches sapphire that Manuel used to check the setup calibration (eg check entry 1132).

We did the exact same measurement and got similar values (fig 3)  : mean absorption ~ 40 ppm/cm.

However, the sample was really dirty so it we cleaned this sample by wiping alcohol on it and repeated the measurement that gave identical result (fig 4)

It means that despite some issue with the setup, our calibration gives us reasonable results and can be considered to be working again.