Saturable light absorber structure and a device incorporating the structure for regenerating a wavelength division multiplexed signal

1. A saturable light absorber adapted to receive different focused spectral components, wherein the structure of said saturable light absorber comprises microcavities integrated into a substrate and each associated with a respective one of said spectral components, each microcavity comprising a saturable absorber layer delimited by a top reflector and a bottom reflector and being disposed and having dimensions such that it receives only the focused spectral component associated with it.

2. A saturable light absorber according to claim 1 , wherein the effective thickness of each microcavity is matched to the spectral component associated with it to maximize the absorption of the associated focused spectral component in the saturable absorber layer of said microcavity.

3. A saturable light absorber according to claim 1 , wherein the diameter of each microcavity is matched to the spectral component associated with it in order to match the admission angle of light at the surface of said microcavity to the angle to said surface of the incident light beam corresponding to the focused spectral component associated with said microcavity.

4. A saturable light absorber according to claim 1 , wherein the top reflector and the bottom reflector are made of metal or a multilayered dielectric or semiconductor.

5. A saturable light absorber according to claim 1 , wherein the saturable absorber layer includes a ternary material active layer with multiple quantum wells.

6. An optical regenerator comprising a wavelength division demultiplexer for receiving a WDM signal and for focusing the spectral components of said WDM signal at respective spatially separated points, said optical regenerator further comprising a saturable light absorber structure adapted to receive said focused spectral components, wherein said saturable light absorber structure comprises integrated microcavities in a substrate each associated with a respective spectral component, each microcavity comprising a saturable absorber layer delimited by a top reflector and a bottom reflector and being disposed and having dimensions such that it receives only the focused spectral component that is associated with it.

7. An optical regenerator according to claim 6 , wherein the demultiplexer comprises a pair of lenses, one on each side of a grating.