Sensitivity improvement of a pump–probe set-up for thin film and microstructure metrology

Video Ultrasonics by Pulsed TV Holography: A New Capability for Non-Destructive Testing of Shell Structures

“…These techniques make use of very short stress pulses, generated by thermoelastic deformation of the surface irradiated by an ultrashort optical pulse, that propagate across the specimen and are subsequently detected by another optical probing pulse after a controlled delay. The detection principle is usually the change in the specimen optical reflectivity (Thomsen et al 1986;Rossignol et al 2005;Vollmann et al 2002), although the change in the surface slope (OBD) (Wright and Kawashima 1992) and interferometric detection (Hurley and Wright 1999) have also been reported. The fine achievable temporal resolution (of the order of picoseconds), lateral resolution (of the order of micrometers), and the specific and expensive equipment needed make these techniques especially adequate for characterizing microstructures and thin films in laboratory, but not well-suited for macroscopic industrial inspection where the temporal and spatial scales are much larger.…”

Internal Vibrations of Edge Dislocation Dipoles

“…The commercial apparatus works with the frequencies up to 10 GHz, using special equipment, the ultrasound frequency 600 GHz was reached in thin foils [7]. The main problem is a strong attenuation increase at higher frequencies, especially in metals.…”

“…In the last equation the effective mass m of a dislocation per unit length can be estimated [7] as m = ρb 2 ,where ρ is the mass density. For example, for copper, G = 45. , that is, ω S is in the range of 100 GHz, that is, the frequencies f in the range of 10 GHz.…”

Acoustic Waves: A Probe for the Elastic Properties of Films

“…It is nowadays implemented by femtosecond laser pulses, and is intrinsically suited to characterize thin supported films and multilayers. It follows the optical pump-and-probe scheme (Belliard et al, 2009;Bienville et al, 2006;Bryner et al 2006;Vollmann et al 2002). The pump beam, a femtosecond laser pulse, is focused, by a spherical lens, at the specimen surface and, at least partially, absorbed.…”