A superluminescent light emitting diode, SLED, device comprising: front and back facets (16, 18); a substrate; a first epitaxial stack (2.1, 3.1, 4.1) arranged on the substrate and including in sequence along an epitaxial growth axis: one or more first n-type doped layers (2.1), one or more first active layers (3.1) made of a first semiconductor material and forming a first active region dimensioned and configured to generate and amplify light emission over a first wavelength range of between 3 nm and 100 nm at full width half maximum, and one or more first p-type doped layers (4.1), wherein the first epitaxial stack has a first ridge formed in the first p-type doped layers and extending at least part way from the front facet to the back facet to induce a first waveguiding region in the first active layers that defines at least part of a first optical path between the front and back facets; and a second epitaxial stack (2.2, 3.2, 4.2) arranged on the substrate alongside the first epitaxial stack and including in sequence along the epitaxial growth axis: one or more second n-type doped layers (2.2), one or more second active layers (3.2) made of a second semiconductor material different from the first semiconductor material and forming a second active region dimensioned and configured to generate and amplify light emission over a second wavelength range of between 3 nm and 100 nm at full width half maximum, and one or more second p-type doped layers (4.2), wherein the second wavelength range is different from the first wavelength range, and wherein the second epitaxial stack has a second ridge formed in the second p-type doped layers separated from the first ridge by a lateral distance and extending at least part way from the front facet to the back facet to induce a second waveguiding region in the second active layers that defines at least part of a second optical path between the front and back facets. front and back facets (16, 18); a substrate; a first epitaxial stack (2.1, 3.1, 4.1) arranged on the substrate and including in sequence along an epitaxial growth axis: one or more first n-type doped layers (2.1), one or more first active layers (3.1) made of a first semiconductor material and forming a first active region dimensioned and configured to generate and amplify light emission over a first wavelength range of between 3 nm and 100 nm at full width half maximum, and one or more first p-type doped layers (4.1), wherein the first epitaxial stack has a first ridge formed in the first p-type doped layers and extending at least part way from the front facet to the back facet to induce a first waveguiding region in the first active layers that defines at least part of a first optical path between the front and back facets; and a second epitaxial stack (2.2, 3.2, 4.2) arranged on the substrate alongside the first epitaxial stack and including in sequence along the epitaxial growth axis: one or more second n-type doped layers (2.2), one or more second active layers (3.2) made of a second semiconductor material different from the first semiconductor material and forming a second active region dimensioned and configured to generate and amplify light emission over a second wavelength range of between 3 nm and 100 nm at full width half maximum, and one or more second p-type doped layers (4.2), wherein the second wavelength range is different from the first wavelength range, and wherein the second epitaxial stack has a second ridge formed in the second p-type doped layers separated from the first ridge by a lateral distance and extending at least part way from the front facet to the back facet to induce a second waveguiding region in the second active layers that defines at least part of a second optical path between the front and back facets.