A laser light source comprising: a gain chip configured to amplify light passing therethrough; a retro reflecting prism ( 45, 70, 81) having a a planar diffraction grating on an outer surface of said retro reflecting prism, a planar entrance face and a reflector at right angles to said planar diffraction grating, wherein said planar diffraction grating is arranged to receive a beam of light emitted by said gain chip traveling along an input light direction and passing through said planar entrance face, return a diffracted light beam to said gain chip along said input light direction and generate an output light beam that is reflected by the reflector and passes through the planar entrance face along an ouput light direction, said retro reflecting prism further having a pivot axis being parallel to a junction of said planar diffraction grating and said reflector; and a first actuator that causes said retro reflecting prism to rotate about said pivot axis in response to a control signal being coupled to said first actuator; characterized in that said pivot axis is displaced from said planar entrance face and from said junction along a normal to said entrance face that passes through said junction such that said pivot axis is within said retro reflecting prism; wherein said pivot axis is displaced from said junction by a value Xc=(h/2)(1-n1/n2), wherein h is the length of the planar entrance face in the plane perpendicular to said pivot axis and wherein the index of refraction of the medium outside of retro reflecting prism is denoted by n1 and the index of refraction of the material from which retro reflecting prism is constructed is denoted by n2. a gain chip configured to amplify light passing therethrough; a retro reflecting prism ( 45, 70, 81) having a a planar diffraction grating on an outer surface of said retro reflecting prism, a planar entrance face and a reflector at right angles to said planar diffraction grating, wherein said planar diffraction grating is arranged to receive a beam of light emitted by said gain chip traveling along an input light direction and passing through said planar entrance face, return a diffracted light beam to said gain chip along said input light direction and generate an output light beam that is reflected by the reflector and passes through the planar entrance face along an ouput light direction, said retro reflecting prism further having a pivot axis being parallel to a junction of said planar diffraction grating and said reflector; and a first actuator that causes said retro reflecting prism to rotate about said pivot axis in response to a control signal being coupled to said first actuator; characterized in that said pivot axis is displaced from said planar entrance face and from said junction along a normal to said entrance face that passes through said junction such that said pivot axis is within said retro reflecting prism; wherein said pivot axis is displaced from said junction by a value Xc=(h/2)(1-n1/n2), wherein h is the length of the planar entrance face in the plane perpendicular to said pivot axis and wherein the index of refraction of the medium outside of retro reflecting prism is denoted by n1 and the index of refraction of the material from which retro reflecting prism is constructed is denoted by n2.