A semiconductor-based optical mode transformer (100, 100, 100 ') is described for coupling an optical mode of an optical fiber (3) with an optical mode of a waveguide (2a).

An optical device is disclosed which includes a waveguide (100) that supports a first optical mode in a first region and a second optical mode in a second region.

The vertical confinement of an optical mode of an optical signal is altered by sending a signal to the electrode.

In another aspect, an optical mode division demultiplexing can be performed by coupling an optical waveguide and an optical resonator.

The device may be used as an optial mode transformer.

The core and cladding are arranged to form an optical waveguide that supports a propagating optical mode.

The system also includes a substantially planar high-contrast grating (HCG) lens to convert an optical mode of the optical signal to provide a converted optical signal having a mode-isolating intensity profile.

The ridge-shaped active region is used to confine a selective optical mode for optical modulation.

In a preferred embodiment, concatenated tapered and adiabatic sections can be used to provide for reduced optical reflection loss and reduced optical mode mismatch.

An architecture which makes it possible to avoid optical mode hopes and several digital examples proving that inventive principles are applicable to standard materials are also disclosed.

An index step created by the buried heterojunction is substantially removed from the optical mode.

A ridge waveguide (24) is used to confine the optical mode.

At least the first optical guided mode is excited by the emitted broadband light without the second optical guided mode being excited by the emitted broadband light.

Each of the cavities localizes at least one optical mode.

The fundamental optical mode supported by the composite waveguide varies along the length of the composite waveguide so that, in a laser, the laser mode is enlarged and is a better match to single mode optical fibre.