Laser-ultrasound spectroscopy apparatus and method with detection of shear resonances for measuring anisotropy, thickness, and other properties

A laser-ultrasonic spectroscopy device, comprising:

• a laser for directing a laser pulse to an object to generate elastic waves in the object;
• a laser-interferometer for detecting surface displacements in the object arising from the elastic waves generated by the laser pulse of said laser;
• a converter for converting the surface displacements detected by said laser-interferometer from the time domain to the frequency domain to obtain frequency domain data;
• a shear resonance detector for detecting and measuring at least one shear resonance in accordance with the frequency domain data;
• and
• a property calculator for calculating at least one of a geometrical property, a physical property, and a microstructural property of the object in accordance with the at least one shear resonance detected and measured by said shear resonance detector,
• wherein the elastic waves are generated in the object without frequency sweeping, and
• wherein the laser pluse generates a broadband ultrasonic pulse in the object, whereby said laser simultaneously excites a broad frequency spectrum of elastic waves in the object.

A method for generating and optically detecting a shear resonance in an object, said method comprising:

• applying a radiation pulse from a pulsed source of radiation to an object to generate elastic waves therein;
• optically detecting, using an interferometer, the elastic waves generated in the object by said applying step;
• and
• analyzing the elastic waves optically detected in the object by said detecting step, said analyzing step comprising a shear resonance identifying step of identifying at least one shear resonance in the object in accordance with the elastic waves optically detected in the object by said detecting step,
• wherein the elastic waves are generated in the object without frequency sweeping, and
• wherein the radiation pulse generates a broadband ultrasonic pulse in the object, whereby said applying step simultaneously excites a broad frequency spectrum of elastic waves in the object.

A method comprising:

• directing a laser pulse to an object to generate elastic waves in the object;
• optically detecting, using an interferometer, surface displacements in the object arising from the elastic waves generated by the laser pulse of the laser;
• converting the surface displacements detected by said detecting step from the time domain to the frequency domain to obtain frequency domain data;
• a shear resonance detecting step of detecting at least one shear resonance in accordance with the frequency domain data;
• and
• calculating properties of the object in accordance with the at least one shear resonance detected by said shear resonance detecting step,
• wherein the elastic waves are generated in the object without frequency sweeping, and
• wherein the laser pulse generates a broadband ultrasonic pulse in the object, whereby said directing step simultaneously excites a broad frequency spectrum of elastic waves in the object.

An apparatus, comprising:

• a pulsed source of radiation for applying a radiation pulse to an object to generate elastic waves therein;
• an interferometer for optically detecting surface displacements in the object arising from the elastic waves generated by the radiation pulse generated by said pulsed source of radiation;
• and
• a resonance detector for detecting, in accordance with the surface displacements detected by said interferometer, a resonance of elastic waves propagating in the direction of the thickness of the object and having a polarization along an axis perpendicular to the direction of propagation,
• wherein the elastic wave generated in the object without frequency sweeping, and
• wherein the radiation pulse generates a broadband ultrasonic pulse in the object, whereby said pulsed source of radiation simultaneously excites a broad frequency spectrum of elastic waves in the object.