Results of experimental optoacoustic investigations of femto-and nanosecond laser pulse extinction by muscular and fatty biotissues, skin, and milk and thresholds of optical breakdown of these tissues are presented. It is demonstrated that the depth of short laser pulse penetration into the biotissue is the same as of long pulses. However, the amplitude of the acoustic response to the interaction of femtosecond laser pulses with the biotissue exceeds several times the amplitude of response to the interaction with nanosecond pulses of the same energy and spectral structure.
Using two optical acoustic approaches we experimentally investigated spatial location of filament zone of propagation channel of focused laser radiation. For femtosecond pulses passing in air it was shown that nonlinear focus length had spatial scale of 1/P at initial power P moderate for self-focusing and at optical system focus distance significantly lower than Rayleigh beam length. The results of experimental optical acoustic investigation of femto-and nanosecond pulses attenuation by some biological tissues (muscular tissue, adipose tissue, cutaneous covering, and milk) and optical breakdown thresholds on these one are presented. It was shown that penetration depth of short laser pulse radiation into biological tissues is the same as for longer one. However, amplitude of acoustic response to a process of interaction of femtosecond laser pulse with biological tissue is larger in several times than that to interaction with nanosecond pulses of the same power and spectral distribution. The obtained threshold values can be interesting for tabulation of limit allowable levels of irradiation at work with laser radiation. Such values are unknown for femtosecond laser pulses today.
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