I tried to reproduce experimentally the situation of last simulations (Elog entry 288), but the data are a bit confusing. I think I'm missing something.

Here is what I did:

I made a scan of the bulk reference sample (blue data in the plot), and then I placed the tama-size sapphire sample in front of it, at about 15mm, and repeated the scan (black data in the plot).

Pictures of the setup: 2,3

With the sapphire sample, I noticed that:

 - the signal is very low

 - the phase signal has a strange shape.

This phase shape makes me think that the sapphire sample might reflect the transmitted pump beam back and then heat the reference sample again. This would change a lot the signal shape. So I placed the sapphire sample further, at about 45mm, and a bit tilted (about 3°) so the reflected beam would not go back on the measured point. Then I repeated the scan (red data in the plot). Picture 4. Then I tilted more the sample (about 6°) and repeated the scan (green data). I couldn't tilt the sample more because, otherwise, the probe beam would go out of the prism mirror.

Every time I moved the sapphire sample, I had to tune the focusing lens to center the probe beam on the detector.

I feel confused by the fact that changing the position of the sapphire sample make so different signals.