Parallel Detection in Picosecond Ultrasonics with both Commercial and Custom Array Detection

Picosecond laser ultrasonics is a well established technique for measurement and diagnosis of microand nano-scale structures. One of the major drawbacks preventing widespread acceptance of this technique is that the data acquisitions speeds are slow making imaging applications impractical. We are engaged in a research program to accelerate the data capture rate by use of parallel detection methods. This involves both optical and electronic developments. We have investigated the use of commercial and custom built integrating linear array detectors, which combined with suitable algorithms for signal reconstruction can attain comparable performance to a typical photodetector and lock-in amplifier combination. Modulation depths below 1 part in 10, over 512 pixels can be readily detected with the commercial detector and smaller modulation depths are possible with the custom detector on account of the larger well depth and hence higher signal to noise ratio. Results demonstrating an order of magnitude increase in data acquisition speed will be presented.