Abstract: A method and device for converting an input light signal into an output light signal, in an optical component is described. An input light signal, at a first wavelength, and a first light beam which may be at a second wavelength, are received at the component. The input light signal and the first light beam interfere in the component to form an interference pattern, which modifies a reflectivity spectrum of the component to increase the reflectivity of the component in a portion of the reflectivity spectrum. A second light beam, having a second wavelength corresponding with a wavelength within the portion of the reflectivity spectrum, is also received at the component and is then reflected from the component, in dependence upon the portion of the reflectivity spectrum, to generate the output light signal at the second wavelength. This enables conversion of light signals to signals at a different wavelength.

Abstract: A method and device for converting an input light signal into an output light signal, in an optical component is described. An input light signal, at a first wavelength, and a first light beam which may be at a second wavelength, are received at the component. The input light signal and the first light beam interfere in the component to form an interference pattern, which modifies a reflectivity spectrum of the component to increase the reflectivity of the component in a portion of the reflectivity spectrum. A second light beam, having a second wavelength corresponding with a wavelength within the portion of the reflectivity spectrum, is also received at the component and is then reflected from the component, in dependence upon the portion of the reflectivity spectrum, to generate the output light signal at the second wavelength. This enables conversion of light signals to signals at a different wavelength.

Abstract: The output frequency of a semiconductor laser beam is stabilized using a grating or another optical device which has an interaction with the beam whose parameters are sensitive to the beam frequency. The grating (130) generates positive and negative first order diffracted beams (132, 134), whose angle of diffraction is sensitive to the beam frequency, and is detected by split photodetectors AB, CD respectively. In the event of a change in beam frequency the outputs from the photodetectors AB, CD will vary to provide an error signal for the laser frequency. This error signal is insensitive to variations in angular alignment between the beam and the diffraction grating. This is because variations in frequency and variations in angular alignment cause different changes in the outputs of the photodetectors AB, CD.