Devices and methods for low voltage optical modulation
An electro-optic modulation structure 110 , a method for fabrication of the electro-optic modulation structure, and a method of optical modulation derived from an electro-optic modulation structure with low voltage of operation are disclosed. The low voltage operation of the electro-optic modulator is realized by designed electro-optic modulation structures that include the light confining waveguide 114 , overclad layer 120 and modulating electrode structure 116 for applying modulation voltages that are directed towards a low voltage operation of the electro-optic modulation 110 device upon consideration of optimal optical loss.
1. An electro-optical modulator, comprising:
a base substrate;
a waveguide having a first surface proximate said base substrate and a second surface opposite said first surface and remote from said base substrate, said waveguide including a ledge projecting from said second surface thereof;
a first electrode, including a first section in contact with said second surface of said waveguide to one side of said ledge thereof, a first joint at an end of said first section proximate said ledge of said waveguide, and a second section extending from said first joint and being offset relative to said first section such that said second section has a terminal end located a first spaced distance from said second surface of said waveguide and a second spaced distance from said ledge of said waveguide;
a second electrode, including a third section in contact with said second surface of said waveguide to an opposite side of said ledge thereof, a second joint at an end of said third section proximate said ledge of said waveguide, and a fourth section extending from said second joint and being offset relative to said third section such that said fourth section has a terminal end located a third spaced distance from said second surface of said waveguide and a fourth spaced distance from said ledge of said waveguide, said fourth section of said second electrode being spaced from said second section of said first electrode by a fifth spaced distance, and said second joint of said second electrode being spaced from said first joint of said first electrode by a sixth spaced distance, which is different than said fifth spaced distance;
a cladding layer having a first portion interposed between said first surface of said waveguide and said base substrate and a second portion interposed between said second surface of said waveguide and said second and fourth sections of said first and second electrodes, respectively;
a first capacitor established by said first and second joints of said first and second electrodes, respectively, upon application of an electrical potential to at least one of said first and second electrodes; and
a second capacitor established by said second and said fourth sections of said first and second electrodes, respectively, upon application of an electrical potential to at least one of said first and second electrodes.
2. The electro-optical modulator of claim 1 , wherein said plurality of capacitors comprise a base capacitor and a top capacitor that are connected to form a dual-capacitor structure and create enhanced electromagnetic fields in said waveguide.
3. The electro-optical modulator of claim 1 , further comprising:
a beamsplitter at a first end of said modulator; and
a beam combiner at a second end of said modulator, opposite said beamsplitter.
4. The electro-optical modulator of claim 3 , wherein said beamsplitter and said beam combiner are each formed from directional couplers.
5. The electro-optical modulator of claim 3 , wherein said base and top capacitors partially surround said cladding layer.
6. The electro-optical modulator of claim 3 , wherein said beamsplitter and said beam combiner are implemented as multi-mode interferometers.
7. The electro-optical modulator of claim 3 , wherein said beamsplitter and said beam combiner are implemented through Y-branches.
8. The electro-optical modulator of claim 3 , wherein said beamsplitter and said beam combiner are implemented through anti-symmetrical branches.
9. The electro-optical modulator of claim 1 , wherein said waveguide comprises lithium niobate.
10. The electro-optical modulator of claim 1 , wherein said first and second electrodes comprise gold in thin films.
11. The electro-optical modulator of claim 1 , wherein said cladding layer completely surrounds said waveguide.
12. The electro-optical modulator of claim 1 , wherein said cladding layer comprises silicon dioxide.
13. The electro-optical modulator of claim 1 , wherein said modulator is configured to operate as a phase shifter.
14. The electro-optical modulator of claim 1 , wherein said modulator is configured to modulate the intensity of optical signals.
15. The electro-optical modulator of claim 1 , wherein said cladding further comprises a buried layer interposed between said substrate and said waveguide.
16. The electro-optical modulator of claim 1 , wherein said waveguide comprises a plurality of arms, and wherein opposite electric fields are applied to two arms of said plurality of arms.
17. The electro-optical modulator of claim 1 , wherein said first electrode and said second electrode are coplanar.
18. The electro-optical modulator of claim 1 , wherein said modulator forms an optical switch.