Patent ID: 7813604

Claim:
An optical apparatus comprising: a waveguide substrate; a first planar optical waveguide formed on the substrate comprising a first transmission core and cladding; a second planar optical waveguide formed on the substrate comprising a second transmission core and cladding; a third planar optical waveguide formed on the substrate comprising a third transmission core and cladding; a laser positioned so as to launch at least a portion of its optical output to propagate along the first transmission core toward a proximal end thereof; a photodetector positioned so as to receive at least a portion of an optical signal propagating along the second transmission core away from a proximal end thereof; and a branched splitter planar optical waveguide comprising a splitter main core segment, a splitter first branch core segment, a splitter second branch core segment, and splitter cladding, the two splitter branch core segments being joined at their respective proximal ends with the proximal end of the splitter main core segment, wherein: the splitter main core segment is connected at its distal end to the proximal end of the first transmission core and tapers toward the first transmission core; the splitter first branch segment is connected at its distal end to the proximal end of the second transmission core and tapers toward the splitter main core segment; the splitter second branch segment is connected at its distal end to the proximal end of the third transmission core and tapers toward the splitter main core segment; a proximal portion of the first transmission core forms obtuse angles with respect to proximal portions of the second and third transmission cores, and proximal portions of the second and third transmission cores form an acute angle with respect to one another; a longitudinal slot having substantially parallel edges separates the first and second branch core segments from one another, the slot extending from near the proximal ends of the second and third transmission cores to the proximal end of the splitter main core segment, the slot being substantially filled with cladding; and the branched splitter planar optical waveguide is arranged so that (i) a first fraction of the laser optical output propagating along the first transmission core toward the proximal end thereof is transferred to the second transmission core to propagate away from a proximal end thereof by optical propagation along the splitter main core segment and the splitter first branch core segment, and (ii) a second fraction of the laser optical output propagating along the first transmission core toward the proximal end thereof is transferred to the third transmission core to propagate away from a proximal end thereof by optical propagation along the splitter main core segment and the splitter second branch core segment.