Nondestructive evaluation of aircraft composites using transmissive terahertz time domain spectroscopy.

Terahertz time domain spectroscopy (TDS) was assessed as a nondestructive evaluation technique for aircraft composites. Damage to glass fiber was studied including voids, delaminations, mechanical damage, and heat damage. Measurement of the material properties on samples with localized heat damage showed that burning did not change the refractive index or absorption coefficient noticeably; however, material blistering was detected.

Real-time, frequency-translated holographic visualization of surface acoustic wave interactions with surface-breaking defects.

A real-time, frequency-translated holographic imaging system has been developed by use of bacteriorhodopsin film. The system provides a capability for imaging surface acoustic waves and has been utilized to detect and characterize surface-breaking defects through near-field ultrasonic scattering effects. Frequency-plane filtering was used to discriminate between ultrasonic standing-wave and near-field scattering features, dramatically enhancing the holographic visualization of the defect sites.

Characterization of MEMS transducer performance using near-field scanning interferometry.

Sophisticated ultrasonic transducer microarrays based on micro-electro-mechanical-systems (MEMS) technologies are quickly becoming a reality. A current challenge for many researchers is characterizing the dynamic performance of these and other micro-mechanical devices. In this work, the performance characteristics of a MEMS ultrasonic transducer array were successfully measured using a scanning heterodyne interferometer system.

Temperature and pulse-duration dependence of second-harmonic generation in CdGeAs2.

A detailed investigation of frequency doubling of a transversely excited atmospheric CO2 laser operating at 9.55 microm with a CdGeAs2 crystal was carried out. The temperature of the crystal was varied between 80 and 295 K to maximize the frequency-doubled energy.