Multi-stable cavity processor

A low energy optical processing apparatus in the form of an optical cavity, said apparatus comprising:

• reflecting means for providing at least one end portion of said optical cavity;
• a gain medium excitable into at least a state of fluorescence wherein said medium spontaneously emits light to generate a wavefront which propagates along a path in said cavity;
• first spatial light modulator means, disposed within said path, for imposing a first spatial pattern on a wavefront generated by said gain medium and propagating along said path;
• and
• second spatial light modulator means, disposed within said path, for imposing a second spatial pattern on a wavefront which has been generated by said gain medium and which has had a first spatial pattern imposed thereon by said first spatial light modulator means, whereby when there is matching between said second spatial pattern imposed by said second spatial light modulator means and said first spatial pattern imposed by said first spatial light modulator means, light spontaneously emitted by said gain medium to generate said wavefront will propagate through said optical cavity and be reflected back to said gain medium by said reflective means to induce stimulated emission in said medium, and when there is substantially no matching between said second spatial pattern and said first spatial pattern, said second spatial light modulating means will substantially prevent light emitted by said gain medium to generate said wavefront to propagate through said cavity and be reflected back to said gain medium.