Figure 7.

PA SNR as a function of the laser excitation energy. PA SNRs were acquired at different laser excitation energies and at a fixed depth of 1 cm and a fixed excitation wavelength of 750 nm for a 6-µm carbon fiber. The SNRs are 13.08, 14.66, 13.68, 17.89, 18.67, and 17.83 dB at energies of 50, 60, 70, 80, 90 and 100 mJ/pulse (directly measured from the laser output), respectively. The SNR improved slightly when the input laser pulse energy was increased from 50 to 100 mJ. PA, photoacoustic; SNR, signal-to-noise ratio.