  The concept of potential energy landscapes is applied in many areas of
science. We experimentally realize a random potential energy landscape (rPEL)
to which colloids are exposed. This is achieved exploiting the interaction of
matter with light. The optical set-up is based on a special diffuser, which
creates a top-hat beam containing a speckle pattern. This is imposed on
colloids. The effect of the speckle pattern on the colloids can be described by
a rPEL. The speckle pattern as well as the rPEL are quantitatively
characterized. The distributions of both, intensity and potential energy
values, can be approximated by Gamma distributions. They can be tuned from
exponential to approximately Gaussian with variable standard deviation, which
determines the contrast of the speckles and the roughness of the rPEL.
Moreover, the characteristic length scales, e.g. the speckle size, can be
controlled. By rotating the diffuser, furthermore, a flat potential can be
created and hence only radiation pressure exerted on the particles.
