Members: Tatsumi, Manuel
Measured the bulk reference sample: Pump_power=30mW, Chopper=430Hz; AC=74mV; DC=3.94V; Abs=1.16/cm; --> calibration factor R=0.55W-1. fig.
Measured the surface reference sample: Pump_power=30mW, Chopper=430Hz; AC=380mV; DC=4.75V; Abs=0.22; --> calibration factor R=12W-1. fig.
Both values of R are consistent with the calibrations we made last year (considering a repeatability of 5-10%).
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Measured the shinkousha little sample (1.5"diameter) with pump maximum power 9W.
Scan along z axis: fig. Today's measurement looks noisier because I didn't apply the filter
Resolved map: fig. It show the same unhomogeneus pattern al last time we measured it.
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Measured the 2 sapphire tama-sized samples Hirose-san sent us few months ago:
the translation stage is too weak to bear 100mmx60mm samples, so we tried to put a height tunable jack on the table and the new mirror mount over it. Unfortunately, because of the translation stage position, there was not room enough to to reach the center of the sample. So we changed the jack with some heavy blocks and a V-shape. Then we could reach the center of the sample. We measured the probe AC noise and we found that with the probe passing through the sample, the noise (~50microV) is double respect to the noise without the sample (25microV). This means that a large part of the noise is due to the sample vibrations. So we put a rubber sheet below the block. But the noise doesn't change considerably. fig.
So we have ~50microV of noise level, which correspond in ppm/cm for sapphire at 9W pump power to ~50e-6V*3.34/6.5/9W/0.55W-1 = ~6ppm/cm
The specs say 5ppm/cm for silica at 1W, which for sapphire (3.34 correction factor) and 9W, correspond to about 2ppm/cm. So we have a noise level higher than what the specs say.
To measure the signal I take the mean of the AC signal (lock-in time constant 1s) over 100s
| AC mean 0W | AC mean 9W | absorption | |||
| [microV] | [microV] | [ppm/cm] | |||
| sample#1 | point A | 35 | 43 | 1 ± 4 | |
| sample#1 | point B | 37 | 53 | 2 ± 4 | |
| sample#1 | point C | 36 | 78 | 5 ± 4 | |
| sample#1 | point D | 43 | 49 | 1 ± 5 | |
| sample#1 | point E | 42 | 79 | 4 ± 5 | |
| sample#2 | point A | 37 | 48 | 1 ± 4 | |
| sample#2 | point B | 44 | 51 | 1 ± 5 | |
| sample#2 | point C | 35 | 43 | 1 ± 4 | |
| sample#2 | point D | 46 | 16 | -3 ± 5 | |
| sample#2 | point E | 44 | 30 | -1 ± 5 |
The point positions are shown in the picture. As best as I could do with this setup, the positioning has a 3mm error.
The measured absorption value is always below the noise.
