Spectra of laser acoustic signals in water

To get the spectra of laser acoustic signal (LAS) in water induced by CO2 laser pulse, and the relation to the parameters of laser pulse (LP). A peak-tail approximation of the actual CO2 LP is used to get the theoretical thermoelastic LAS, after FFT (Fast Fourier Transformation), the affection of the waveform parameters to the LAS spectra is given. And the higher frequency part is affected mainly by the peak while the lower frequency part is affected by the tail. Affection of attenuation to the spectra of LAS is researched and showed spectra at different distance to the source. Experimental research shows that: The spectra of LAS remain unchanged at the same experiment condition and by reducing gas pressure to 5kPa, LAS with peak frequency at 16 kHz is obtained.