Reduction in Bend Losses of a Buried Waveguide on a Silicon Substrate by Adjusting the Core Location

Core depth determination of a slightly buried Si-wire waveguide with a reduced bend loss

“…In our previous paper, 14) we have treated a weakly guiding waveguide with a square-shaped core. The effectiveness of adjusting the core depth has been explained in terms of an extended field caused by the adjacent air region and a folded field generated at the air-cladding interface.…”

“…We should recall that the appearance of a minimum bend loss is attributed to the opposing effects of the extended and folded fields distributing in the cladding. 14) In the case of the TM mode, the considerable electric field exists in the top region of the core, since the electric flux density is continuous along the core/cladding interface with a large refractive index difference. As a result, we can expect the situation similar to that observed in a weakly guiding waveguide.…”

“…In a buried silica waveguide, we have proposed a simple technique to reduce the total bend loss, 14) in which only the distance between the core and the air-cladding interface is adjusted. The proposed technique has the advantage that an additional technique, such as offsetting the core axis, 12,[15][16][17] can readily be combined to further reduce the transition loss.…”

“…It has been shown in a weakly guiding waveguide that a minimum PBL is obtained when the air-cladding interface is placed at the position where the field amplitude decays to 12% of its peak. 14) Keeping this fact in mind, we determine a core depth so as to reduce the PBL in a Si-wire waveguide. As a result, the PBL for the TM mode is minimized when the air-cladding interface is placed at the position where the field amplitude decays to 5% of its peak.…”

Surface-plasmonic right-angle waveguide amplifiers

“…[8] reported a low-loss 90 • waveguide bend composed of clothoid, and the bending loss with the bending radius of 4.0 µm has 90% reduction compared with normal bend. In a buried dielectric waveguide, waveguide core location could be adjusted to suppress a leaky wave so that pure bend and transition losses can be reduced [9]. A bent embedded waveguide with a loaded metal film was proposed to generate the surface plasmon-polariton mode for the transverse-magnetic wave [10].…”