Abstract | The usual frequency bandwidth of laser-ultrasonics is in most cases of order 1 to 30 MHz. Although this is sufficient for most applications, applications involving attenuation measurements in weakly attenuating materials, or velocity measurement in thin samples or coatings may require a much higher detection bandwidth. By shortening the generation light pulse and improving the interferometer electronics, laser-ultrasonic bandwidths of 500 MHz were achieved. Much higher bandwidths (up to 100 GHz) have been achieved by others using delayed femtosecond laser pulses, but what distinguishes our technique is the capability to acquire a full A-scan with a single generation pulse. The capabilities of high frequency laser-ultrasonics will be illustrated with measurements in aluminum foil and sheet, fused quartz, and galvanized steel. |
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