We study numerically and experimentally the transition from convective to absolute dynamical instabilities in an optical system composed of a bulk photorefractive crystal subjected to a single optical feedback. We demonstrate that the convective regime is directly related to the bistability area in which the homogeneous steady state coexists with a Turing pattern solution. Outside this domain, the system exhibits either a homogeneous steady state or an absolute dynamical regime. Moreover, an external background illumination applied onto the nonlinear medium is used as an external parameter for controlling the size of the bistability area. We question the role of this parameter and show how the background illumination makes the bistability area even larger.
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