Meaning
Non-destructive testing uses the change in refractive index of a fluid or solid near a heated surface to track energy absorption. In the process of photothermal deflection, a pump laser heats the sample and a second probe laser detects the tiny tilt in its own path as it skims the surface. This technique measures absorption levels that are too low for conventional sensors to notice.
Measurement Accuracy
Shifts in the probe beam reveal exactly how much energy the sample turned into heat. Because photothermal deflection bypasses direct contact, it avoids contaminating the test subject. The resolution of this method reaches thresholds relevant for the purest optical coatings.
Sensitivity Range
High precision detectors track the angle of the deflected probe beam. Results from photothermal deflection help scientists identify trace impurities in crystals or thin films. It is particularly useful for checking the quality of mirrors used in gravitational wave detectors or high power systems.
Geometric Factors
Distance between the sample surface and the probe laser determines the strength of the signal. If the photothermal deflection signal is weak, operators adjust the alignment to find the region of maximum index gradient. This setup allows for rapid mapping of surface variations.
