In computerchip manufacturing it is extremely important that structures, hidden underneath optically opaque layers, can be observed. A promising technique to do that is by "looking" with extremely high frequency ultrasound, created by rapidly heating a material with a laser pulse. The technique works, but the signals are still too small. In this project we want to investigate methods to improve the strength of these photoacoustics signals.
Enhancing photoacoustic detection sensitivity
As we detect the sound waves with light, the detection sensitivity can be enhanced by using more powerful light sources, or by using a light color that is more sensitive to the sound waves. In addition, we want to increase the surface area where the sound waves are generated and detected, such it matches the size of the structure we would like to "see", to maximise the amount of detected light.
Making stronger sound waves.
The sound waves themselves we can make stronger by maximizing the intensity of the light with which they are made, to values just below the threshold for optical damage. Here also we will study what the effect of the color of the light is with the goal to find a color for which the maximum allowed light intensity is the highest.