Patent ID: 7149381

Claim:
A wavelength selective filter device comprising: a light reflector structure comprising first and second resonator units; and an optical coupler structure coupling light from an input/output of a laser structure to propagate through said light reflector structure, said light reflector structure being operative to reflect light filtered by said first and second resonator units so as to propagate to said input/output of the laser structure, said light reflector structure being configured so as to define two optical paths of substantially the same lengths for light propagation in said first and second resonator units from and to the coupler structure, and wherein said optical coupler structure comprises: first and second waveguides; and a coupling region between an input/output waveguide connected to said input/output of the laser structure and said first and second waveguides, said optical coupler structure being operative to: split input light propagating in said input/output waveguide from the laser structure into first and second light portions of substantially equal power; direct said two light portions to propagate along two spatially separated paths in said first and second waveguides, respectively; and combine light coming from said two paths to propagate through said input/output waveguide to the laser structure.