Two-dimensional photoacoustic imaging of femtosecond filament in water

Abstract

We report a first-of-its-kind optoacoustic tomography of a femtosecond filament in water. Using a broadband (~100 MHz) piezoelectric transducer and a back-projection reconstruction technique, a single filament profile was retrieved. Obtained pressure distribution induced by the femtosecond filament allowed us to identify the size of the core and the energy reservoir with spatial resolution better than 10 µm. The photoacoustic imaging provides direct measurements of the energy deposition into the medium under filamentation of ultrashort laser pulses that cannot be obtained by existing techniques. In combination with a relative simplicity and high accuracy, photoacoustic imaging can be considered as a breakthrough instrument for filamentation investigation.

Transverse structure of femtosecond laser filaments reconstructed with circular scanning-based photoacoustic tomography

“…As shown in figure 1a, the circular PAT system is considered in this paper as this geometry can collect signals over a broad range of angles and very suitable for reconstruction of cross-sectional image. As for fs laser pulses, the heating typically occurs on a timescale much shorter than the characteristic acoustic travel time (a condition called stress confinement), and so the initial pressure rises at a position r  due to energy deposition of filamentation is given by [10] : A r  is adopted from an actual measured cross-sectional images of multifilaments [11] . The image is normalized and smoothed.…”

“…Photoacoustic tomography (PAT) is a potential novel method developed to reconstruct structure images of optical filament and is under development [8] . The optoacoustic tomography had been successfully used to reconstructed the cross-sectional image of single filament in transmission media including air [9] and water [10] . When the incident laser pulse powers widely exceeding the critical power, the beam breaks up into a large number of localized filaments, which is often referred to as multiple filamentation.…”

A comprehensive approach to the characterization of the deposited energy density during laser–matter interactions in liquids and solids

“…The presented above approaches are complicated and comparatively difficult to adopt for real-time determination of the DED. Thereby we performed the photoacoustic imaging technique [32,33], which allows us to retrieve the transversal DED distribution ε(x,y) averaged over an optical axis. This method allows direct observation of the transversal DED distribution.…”

Electronic and vibrational processes in absorbing liquids in femtosecond laser sub- and filamentation regimes: ultrasonic and optical characterization

“…Ultrasonic acquisition has been demonstrated for the last few decades as a versatile direct method of quantifying pulsed laser energy deposition and visualizing related thermal, phasechange and acoustic processes in opaque and transparent materials [11,[23][24][25][26][27][28][29][30][31] Moreover, during the past decade, the ultrasonic acquisition of ultrafast fs-laser energy deposition in transparent media during the filamentation of laser pulses was successfully harnessed to elucidate dimensional sub-critical plasma effects in solids [11], MPA in water [32,33] and imaging and characterization of fs-laser filaments in liquids [34][35][36][37]. Meanwhile, broad-range systematic study of nonlinear 'laser-dielectric' interactions in transparent media, covering both sub-and filamentation regimes and identifying their transition reasons, has not been realized so far to present a complete picture of the fundamental relevant processes and quantification of the key parameters that are involved.…”