Abstract: In a ridge waveguide serial interferometer mode conversion is induced by a first mode conversion section, a phase difference between modes is introduced by propagation over a length of waveguide and optical interference is produced following further mode conversion induced in a second mode conversion section. The first mode conversion section has a first radius of curvature, which is equal to a second radius of curvature of the second mode conversion section. The ridge waveguide interferometer advantageously provides an equal phase dependency as a function of temperature.

Abstract: A Mach-Zehnder interferometer (MZI) incorporates a tunable multimode interference (MMI) coupler comprising a tunable MMI coupler with a tuning electrode on a surface of a tunable MMI region and an electrically insulating region provided within the tunable MMI region. The MMI region is tunable in response to detection of a photocurrent by a photodetector section. Such a tunable MZI is particularly advantageous in enabling a split ratio of an optical splitter, the split ratio and the splitter to be controlled in a particularly efficient manner.

Abstract: In a ridge waveguide serial interferometer mode conversion is induced by a first mode conversion section, a phase difference between modes is introduced by propagation over a length of waveguide and optical interference is produced following further mode conversion induced in a second mode conversion section. The first mode conversion section has a first radius of curvature, which is equal to a second radius of curvature of the second mode conversion section. The ridge waveguide interferometer advantageously provides an equal phase dependency as a function of temperature.

Abstract: An Mach-Zehnder interferometer (500) incorporates a tunable multimode interference coupler comprising a tunable MMI coupler (504) with a tuning electrode (524) on a surface of a tunable MMI region (516) and an electrically-insulating region provided within the tunable MMI region. The MMI region is tuned in response to detection of a photocurrent measured by integrated photodetector section (510, 512). Such a tunable MZO is particularly advantageous in enabling a controlled split tio of an optical splitter.