LEAKY-RAYLEIGH WAVE DETECTION AT AIR-SOLID INTERFACES BY OPTICAL HETERODYNE INTERFEROMETRY

Recent developments have proven optical heterodyne interferometry to b e a sensitive detector for ultrasonic amplitude and phase measurements in transparent materials. In this letter it is shown that this optica l technique is sensitive enough to detect leaky-Rayleigh as well as le aky-lamb waves in air reradiated from solids in the megaHertz region. Probing the leaky wave field at several positions parallel to the soli d surface can yield the Rayleigh wave velocity of both transparent and opaque solids. This method can be used for low optical reflectivity s olid surfaces: thus it can be extended for noncontact nondestructive e valuation applications. (C) 1997 Acoustical Society of America. [S0001 -4966(97)03610-2] PACS numbers: 43.20.Fn, 43.35.Zc [ANN].