Phase modulator for semiconductor waveguide
AssigneeBookham Technology PLC
InventorAndrew Alan House
Life of this patent
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Abstract
An optical phase modulator comprises a semiconductor rib wave guide having P and N doped regions forming a PN junction along the path of the rib with terminals for applying a reverse bias to the junction to extend a carrier depletion zone to alter the refractive index, the PN junction is offset from the central axis of the rib but on application of the reverse bias the depletion zone extends over a central axis of the waveguide.
Claims24
An optical phase modulator comprising a semiconductor waveguide formed from a semiconductor layer with an upstanding rib defining an optical transmission path, the semiconductor of the waveguide having both P-type and N-type doped regions forming at least one PN junction extending along the path of the rib for the length of a phase modulation region, said P-type semiconductor having a highly doped ohmic contact region on the surface of the semiconductor extending along the phase modulation region, said N-type semiconductor having a highly doped ohmic contact region on the surface of the semiconductor extending along the phase modulation region, anode and cathode terminals in contact respectively with the said ohmic contact regions and separated from each other by an insulating layer extending between the terminals, and selectively operable electric supply circuitry connected to said anode and cathode terminals to selectively reverse bias said PN junction or junctions and thereby extend the width of a carrier depletion zone at the or each junction to alter the refractive index along the waveguide.
An optical phase modulator according to any one of the preceding claims in which the width of the rib is substantially 1 μM.
A method of effecting an optical phase shift in a semiconductor waveguide formed from a semiconductor layer with an upstanding rib on the semiconductor layer defining an optical transmission path, the semiconductor of the waveguide comprising both P-type and N-type doped semiconductors forming at least one PN junction extending along the phase modulation region, said P-type semiconductor having a highly doped ohmic contact region on the surface of the semiconductor layer extending along the region at one side of the rib, said N-type semiconductor having a highly doped ohmic contact region on the surface of the semiconductor layer extending along the region at the opposite side of the rib, anode and cathode terminals in contact respectively with said ohmic contact regions and separated from each other by an insulating layer extending over the rib between said terminals, which method comprises applying a voltage to said anode and cathode terminals to reverse bias the or each PN junction and thereby increase the width of carrier depletion zone within the rib and change the refractive index along the waveguide.
Dependencies are inferred from the claim text.