Anti-waveguide routing structure

Abstract

In a first state of an optical switch, a structure in the switch confines an optical mode to propagate along a first, unswitched path. The switch is switched into a second state by reducing the refractive index along the first path, or by increasing the refractive index of a region of the switch outside but adjacent to the first path, until the index within the first path is lower, preferably substantially lower, than that of the adjacent region. This creates an anti-waveguiding section in which light is forced to diverge from the unswitched path both by diffraction and refraction. The refractive index change is produced thermo-optically or electro-optically, for example. In a symmetric planar embodiment, upon actuation, light escapes from the confinement region into two beams deflected symmetrically in lateral directions while remaining vertically confined. In an asymmetric planar embodiment, upon actuation, light from the confinement region escapes in one direction away from the confinement region in the horizontal plane, while remaining confined vertically and in the opposite direction in the horizontal plane. A self-aligned method for fabricating optical switches is also described.

1 . A method for switching an optical switch from a first state to a second state, said optical switch including a structure which in said first state provides confinement against propagation of an optical mode in at least a first direction out of a confinement region, said confinement region having a negative thermo-optic coefficient, 
 comprising the step of heating at least part of said confinement region until at least a first part of said confinement region has a refractive index which is below the index of refraction of a first region of said switch outside of and adjacent to said confinement region in said first direction.