| 摘要 |
<p>The invention relates to a saturable absorber structure (10) with multiple-layer epitaxial heterostructure absorbers. Typically the structure comprises first absorber layers of a quantum well semiconductor QW-material, which has a nonlinearly on radiation intensity dependent optical absorption; first contacting layers of a first optically transparent semiconductor material against a surface or surfaces of said first absorber layers; and a first Bragg-reflector (23). The first contacting layers have lattice fit or pseudomorphism with said first absorber layers. The absorber layer (13, 13a, 13b) of the QW-material has a thickness (S) of at maximum 60 nm. Further, said first optically transparent semiconductor material of the contacting layer (14, 14a, 14b, 14c) is a reactive R-material, which semiconductor material contains two or more main components, at least one dopant (M2), and at least one metallic alloying element (M1) substituting one of said main components and enhancing the incorporation of said dopant(s). The metallic alloying element has a concentration of at least 50 atomic-% of that main component it substitutes. This way the charge carriers originating in said QW-material of the first absorber layer has a first recombination time at maximum 100 picoseconds determined by recombination of the charge carriers at sites of said dopant(s), thus forming a fast saturable absorber.</p> |
