Photothermal common-path interferometry (PCI): new developments

Continuous-wave laser particle conditioning: Thresholds and time scales

“…The dn/dt of the sample creates a phase change that affects a small portion of the HeNe probe laser. The local phase change causes self interference of the probe beam, creating an amplitude difference that is measured via a lock-in amplifier at the frequency of the chopped pump beam [7].…”

Optical absorption of ion-beam sputtered amorphous silicon coatings

“…The absorption of the coatings was measured using photothermal common-path interferometry (PCI) [21]. Section II A briefly describes the method.…”

“…The photothermal common-path interferometry measurement technique [21] uses a strong pump laser beam with small waist (high intensity) to create a thermally induced optical length change in a substrate either by direct absorption or, in this case, by the absorption in a coating applied to the substrate. A weak probe beam, larger in diameter than the pump beam, crosses the pump beam so that only the overlapping portion of the probe beam is affected by the optical length change and is phase shifted.…”

Comparison of Single-Layer and Double-Layer Anti-Reflection Coatings Using Laser-Induced Damage Threshold and Photothermal Common-Path Interferometry

“…The setup was calibrated using a Newport metallic neutral density filter, which had an absorption of 22% at 1064 nm (measured with a Cary 500 spectrophotometer). With these parameters, an optical absorption at 1064 nm of α = 0.02 ppm can be measured using pump powers up to 8.0 W. Further details of the measurement setup and process can be found in [1][2][3]. …”

“…The setup was calibrated using a Newport metallic neutral density filter, which had an absorption of 22 % at 1064 nm (measured with a Cary 500 spectrophotometer). With these parameters, an optical absorption at 1064 nm of  = 0.02 ppm can be measured using pump powers up to 8.0 W. Further details of the measurement setup and process can be found in [1][2][3]. The recorded signal is read from the crossing point of the pump and probe beams that move along the pump propagation direction, i.e., perpendicular to the coating in the z-direction (z-scan) or across the coating in the x-direction (x-scan).…”