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US 6,275,321 B1Granted
Polarization-insensitive optical modulators
AssigneeNortel Networks Limited
InventorsPeter David Greene, Mark Silver, Alfred Rodney Adams
Life of this patent
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AssigneeNortel Networks Limited
InventorsPeter David Greene, Mark Silver, Alfred Rodney Adams
Estimating the term…
The or each strained quantum well layer of a quantum confined Stark effect modulator is provided with a substructure of substructure layers not all having the same lattice constant. The thickness and composition of these substructure layers may be arranged to produce a differential strain that is asymmetric with respect to the mid-plane of the quantum well and so skews the hole wavefunctions for heavy-holes, HH1, and light-holes, LH1, in opposite directions. This enables the choice of composition designed to provide substantial matching of the E1-HH1 and E1-LH1 Stark shifts for one particular polarity of applied field, thereby providing a modulation facility that is substantially polarisation insensitive. Alternatively, the thickness and composition of the layers may be chosen to produce a symmetrical strain profile in which the same effect is provided, but for both polarities of applied field.
A quantum confined Stark effect modulator in which the or each quantum well layer of the modulator has a non-uniform composition that provides, across the thickness of the layer, a non-uniform value of lattice constant to produce a strain profile in the modulator that provides the modulator with substantially matching E1-HH1 and E1-LH1 Stark shifts for at least one polarity of applied electric field from 0 up to 100 kV/cm and zero field E1-LH1 and E1-HH1 transitions that are substantilly degenerate.
Dependencies are inferred from the claim text.