Slotted electrode electro-optic modulator
View Patent ↗A co-planar waveguide interferometric electro-optic modulator is disclosed. A Z-cut lithium niobate electro-optic substrate includes a first and second waveguide that are formed in the lithium niobate electro-optic substrate. An elongate RF electrode at least partially covers one of the waveguides. A slotted electrode is disclosed formed by two elongate substantially-parallel electrodes one of which is at least partially covers the other of the waveguides. At least one electrode is substantially greater, preferably at least twice the width of the elongate RF electrode.
1. A waveguide interferometric electro-optic modulator comprising:
a) first and second waveguides formed in an electro-optic substrate; and,
b) a plurality of electrodes including: an RF electrode having a width W RF ; and a slotted ground electrode including first and second elongate electrically-connected conductive portions having widths W F and W S , respectively defining a slot therebetween;
wherein the first elongate conductive portion is disposed between the RF electrode and the second elongate conductive portion,
wherein W F is at least 20% greater than W RF ,
wherein the RF electrode is positioned over the electro-optic substrate between the first and the second waveguides or at least partially over one of the first and second waveguides; and
wherein the slotted ground electrode has an overall width substantially greater than the width of the RE electrode and dimensioned to reduce a piezoelectric voltage caused by thermal stress, thereby reducing a net phase shift and a resulting bias point sensitivity of the modulator to ambient temperature.
2. A waveguide interferometric electro-optic modulator as defined in claim 1 , wherein the first and second waveguides are coplanar, and wherein the slotted ground electrode is disposed over the other, of the first and second waveguides or between the first and second waveguides, the slot for reducing strain accumulated across the width of the slotted ground electrode.
3. A waveguide interferometric electro-optic modulator as defined in claim 2 , wherein the width of the first elongate portion of the slotted ground electrode is at least twice the width of the RF electrode along at least a substantial part of their lengths.
4. A waveguide interferometric electro-optic modulator as defined in claim 2 , wherein the slotted ground electrode is patterned on the electro-optic substrate.
5. A co-planar waveguide interferometric electro-optic modulator as defined in claim 4 , wherein the two elongate electrodes each have interdigitated members forming a large capacitor structure for providing capacitive coupling at high frequencies.
6. A waveguide interferometric electro-optic modulator as defined in claim 2 , wherein the slotted ground electrode is formed of a first elongate electrode and a second elongate parallel electrode; and wherein a plurality of conductive bridges electrically couple the first and second elongate portions.
7. A coplanar waveguide interferometric electro-optic modulator as defined in claim 2 , wherein the slotted ground electrode has interdigitated members forming a large capacitor structure for providing capacitive coupling at high frequencies.
8. A coplanar waveguide interferometric electro-optic modulator as defined in claim 7 , further comprising a second slotted ground electrode.
9. A coplanar waveguide interferometric electro-optic modulator as defined in claim 7 , wherein one or more of interdigitated members are perpendicular to the RF electrode.
10. A coplanar waveguide interferometric electro-optic modulator as defined in claim 2 , further comprising a second ground electrode.
11. A waveguide interferometric electro-optic modulator as defined in claim 1 , wherein the electro-optic substrate is a Z-cut lithium niobate substrate.