Abstract: In various implementations, a sample cell for optical analysis can include a housing configured to confine a sample to be analyzed. The cell can include at least one planar reflector and at least one concave reflector. The at least one planar reflector can be disposed in the housing to receive light from a light source. The at least one concave reflector can be disposed in the housing with respect to the at least one planar reflector to receive light reflected from the at least one planar reflector and to reflect at least of portion of the light back to the at least one planar reflector. The at least one planar reflector can be configured to reflect at least a portion of the light away from said at least one planar reflector to be analyzed.