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When a laser beam of sufficient energy is incident on a medium, the absorption of the electromagnetic radiation leads to an increase of the local temperature. Due to thermal effects, displacements occur in the medium. These displacements can then propagate as elastic waves. Elastic waves can be separated into two components in a bulk: compression waves, corresponding to a curl-free propagation; and shear waves, corresponding to a divergence-free propagation \cite{aki2002quantitative}. Measures of the compression and shear waves are notably useful for inspecting solids such as a metal to reveal potential cracks or defects \cite{Shan_1993}. In biological tissues, induction of compression waves by laser has been studied with the development of photoacoustic imaging \cite{Xu_2006}, \cite{22442475}. Elastic waves used in photoacoustic imaging are typically of a few megahertz: at this frequency, in a soft tissue, shear waves are quickly attenuated, typically over a few microns, and only compression waves can propagate over a few centimeters.  However, induction of shear waves by laser in soft medium has never been shown - most relevent work has been done recently by Li et al. about the induction of surface acoustic waves by laser in soft tissues \cite{Li_2012}, \cite{Li_2014}. This would yet be of high interest for the development of laser-based shear wave elastography techniques. As its names indicates, shear wave elastography covers the techniques used tomeasure or  map the elastic properties of soft tissues using shear wave propagation \cite{Plewes_1995}, \cite{muthupillai1995magnetic}, \cite{Catheline_1999}. These techniques typically use low frequency (50-500 Hz) shear waves to observe their propagation over a few centimeters. In this article, we study thus the generation of shear waves by a laser beam in a soft medium. We describe theoretically the two regimes occurring at different laser energies. We then propose a physical model to describe the observed phenomena, which is compared quantitatively and qualitatively with the experimental results.