WIDE-ANGLE LOW-LOSS WAVE-GUIDE BRANCHING FOR INTEGRATED-OPTICS

A new wide-angle, low-loss, symmetrical Y-branch waveguide is proposed . The waveguide configuration utilizes ribs for lateral confinement in the planar guiding region underneath. This Y-branch structure can be fabricated easily without an additional process step. Together with a utilization of the multimode interference effect, a local decrease of the waveguide ridge in the wedge part of the Y-branch reduces the radi ation loss. When properly designed, the proposed Y-branch has a radiat ion loss as low as 2.2 dB at a branch angle of 6 degrees with the inde x difference (Delta n/n) as small as 7.1 x 10(-4) at a wavelength of 8 70 nm in the TE fundamental mode as compared to 12.6 dB for a conventi onal Y-branch. The proposed method yields corresponding advantages for waveguide designs with a higher Delta n/n ratio and can also be adapt ed in combination with S-branch designs.