ManuelMarchio - 22:01, Wednesday 10 October 2018 (1007)
Setup parameters
checked the parameters. and compared with the SPTS values
- The width at half maximum of the surface reference scan is 0.65mm, same as the SPTS company.
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I measured the phase of the pump (temporarily removing the filters from the PD). It is -22deg.
This means that for the surface reference, the calibrated phase is -81.5-(-22)=-59.5deg. Same as the SPTS company (-60deg).
The calibrated phase for the bulk reference is -93.5-(-22)=-71.5deg. Somewhat different but similar to the SPTS company (-66deg). - The surface calibration factor (from entry 973) is R=19 W-1, about 10% higher than the SPTS company (16.9 W-1).
Until now, I made a mistake on how to calculate the bulk calibration factor. The power in the formula for R should be the power of pump at the point where the signal is generated, which is the power inside the sample. Considering the Fresnel transmission and the depletion due to high absorption, the power at the middle point of the sample thickness is the incident power times the root squared of the transmission.
- So I measured the transmission of the sapphire. with a power meter T_sapp = 0.86
- I already measured the transmission of the bulk reference sample in entry 990. T_bulk = 0.55
- As absorption value of the bulk reference sample, instead of the nominal value from SPTS, I should use the one I measured with the power meter (entry 990) Abs = 105%/cm
- Using the incident power P_ref=32mW, now the correct calibration factor for bulk is R = AC/DC / ( P_ref*sqrt(T_bulk) * 1.05 ) = 0.78 cm/W
Summary:
- changing the reference absorption value from 116%/cm to 105%/cm reduced the absorption value by 10%
- correcting the power with the transmission coefficient reduced the absorption value of 20% because sqrt(T_bulk/T_sapp)=0.8
So the ratio between my measurement and LMA measurement on the Tama-size sample2 (comparison in entry 984) passed from a factor of about 2 to a factor of about 1.5-1.7
Images attached to this report
