Describe the physical reason why radiation loss from a guided optical mode in a curved waveguide increases as the radius of curvature is reduced. A certain ribbed channel waveguide, 1-μm deep, is...

Describe the physical reason why radiation loss from a guided optical mode

in a curved waveguide increases as the radius of curvature is reduced.

A certain ribbed channel waveguide, 1-μm deep, is used in an OIC for guiding

light of vacuum wavelength λ0 = 6328 A. Loss measurements made on test ˚

sections of the guide have shown that the loss coefficient in a straight sample is

α = 0.3 cm−1, while in a curved section with radius of curvature R = 0.5 mm it

is α = 1.4 cm−1, and in a curved section with R = 0.3 mm it is a α = 26.3 cm−1.

What is the minimum radius of curvature that can be used if α must be less

than 3 cm−1 at all points in the circuit?