Patent ID: 7400800

Claim:
An arrayed waveguide grating type optical multiplexer/demultiplexer circuit, comprising on a flat substrate a plurality of first optical waveguides, a first slab waveguide which is connected to the first optical waveguides, an arrayed waveguide, connected to the first slab waveguide, consisting of a plurality of optical waveguides which sequentially become longer with a prescribed waveguide length difference, a second slab waveguide which is connected to the arrayed waveguides, and a plurality of second optical waveguides which are connected to the second slab waveguide; further comprising: a parabola waveguide in which a width W of the first optical waveguide contacting with the first slab waveguide is defined by the following equation with respect to a propagation axis Z of optical wave, Z=A ( W 2 −W 0 2 )− Z 0 where, A: a coefficient, and A>0, W 0 : a width of the first optical waveguide, and Z 0 : a length from the first slab waveguide; and a taper waveguide in which a width W′ of the second optical waveguide contacting with the second slab waveguide is defined by the following equation with respect to a propagation axis Z of optical wave, Z=A ′( W′−W 0 ′)− Z 0 ′ where, A′: a coefficient, W 0 ′: a width of the second optical waveguide, and Z 0 ′: a length from the second slab waveguide; wherein the length Z 0 is set within a range defined by the following condition, Z a,0 ≦Z 0 ≦Z p,0 where Z a,0 : a parabola waveguide length for which a ratio of the amplitude absolute value between a main peak and first side peaks in the field distribution of the parabola waveguide far-field has an upper limit of 0.217, and Z p,0 : a parabola waveguide length for which a relative phase between the main peak and the first side peaks in the field distribution of far-field has a lower limit of 3.14 radians.