Abstract: Light guide devices comprising an intermediate layer of low refractive index between higher refractive index elements are described. The light guide devices are suitable for use in backlights.

Abstract: Light guide devices comprising an intermediate layer of low refractive index between higher refractive index elements are described. The light guide devices are suitable for use in backlights.

Abstract: An optical amplifier is disclosed comprising a signal semiconductor optical amplifier having a waveguide, forming at least part of a signal path between an input and an output, extending along a signal active region for amplification of a signal. The amplifier also includes a control active region of semiconductor material having a gain which is controllable independently from the gain of the signal active region. The amplifier also includes a laser cavity containing both the signal active region and the control active region and being capable of clamping the gain of the signal active region, and the control active region is arranged not to amplify a signal in the signal path within a predetermined signal band.

Abstract: An array of SOAs integrated in a semiconductor chip 1 is optically coupled to an array of waveguides 12 arranged on a substrate 10 of a passive device by mounting the semiconductor chip 1 on the substrate 10 to form a hybrid optical assembly. The semiconductor chip 1 is manufactured with a redundant array of SOAs. In a first aspect, the array of SOAs A1, A2, etc are arranged with a pitch equal to the predetermined pitch at which the array of waveguides 12 are arranged on the substrate 11 divided by an integer greater than 1. In a second aspect, the SOA A, B, C are arranged at the same predetermined pitch at which the array of waveguides 12 are arranged, but the number of SOAs A, B, C in the array on the semiconductor chip 1 is greater than the number of waveguides 12 arranged on the substrate 10.