Patent ID: 7813407
Filing Date: 2010-10-12
Classification: H01S

Abstract:
1. A laser system, comprising: a laser source which emits a laser beam, the laser source comprising a plurality of emitters for emitting respective beam contributions to the emitted laser beam, the emitted laser beam having a spatial light distribution around an optical axis of the emitted laser beam; first and second optical feedback circuits defining respective first and second resonant cavities and providing optical feedback of respective first and second parts of the emitted laser beam back into the laser source at respective feedback angles relative to the optical axis; and a Fourier lens located in the beam path of the emitted laser beam and defining a Fourier plane; wherein the first optical feedback circuit comprises a first diffractive element generating a first diffracted beam from the first part of the emitted laser beam, the first diffractive element being positioned substantially in the Fourier plane, and a first reflective element reflecting a feedback part of the first diffracted beam back onto the first diffractive element and generating an output beam from an output part of the first diffracted beam, and a second spatial filter which blocks spatial modes of the first diffracted beam, the spatial modes corresponding to angular contributions having an angle relative to the optical axis smaller than a lower cut-off angle, and wherein the second optical feedback circuit comprises a first spatial filter which prevents at least a central portion of the spatial light distribution proximal to the optical axis from being fed back into the laser source, a second diffractive element, and a second reflective element including a reflective surface area, the first spatial filter being formed by an edge portion of said reflective surface area proximal to the optical axis, the second diffractive element being positioned substantially in the Fourier plane of the Fourier lens, and the second reflective element being positioned in the beam path on one side of the optical axis such that the edge portion proximal to the optical axis has a predetermined angular distance from the optical axis.