Optical modulators are described having a Mach-Zehnder interferometer and a pair of RF electrodes interfaced with the Mach-Zehnder interferometer in which the Mach-Zehnder interferometer comprises optical waveguides formed from semiconductor material. The optical modulator additionally comprises a plurality of phase shifters configured to interface with the plurality of interconnected optical waveguides such that at least one phase shifter of the plurality of phase shifters is interfaced with at least one optical waveguide of the plurality of interconnected optical waveguides. A phase shifter controller, including an energy source with a variable output controlled by the controller and a plurality of electrical connections connecting the energy source to each of the plurality of phase shifters, is also included. In various embodiments, the plurality of electrical connections are configured to provide approximately equal power to each of the phase shifting elements from the energy source.

An optical waveguide device including an optical waveguide substrate that has an electro-optic effect, is a crystal having anisotropy in thermal expansion rate, has a thickness set to 10 μm or lower, and includes an optical waveguide and a holding substrate that holds the optical waveguide substrate, the optical waveguide substrate and the holding substrate being joined to each other, in which the holding substrate is formed of a crystal having a lower dielectric constant than the optical waveguide substrate and having anisotropy in thermal expansion rate, and the optical waveguide substrate and the holding substrate are joined to each other such that differences in thermal expansion rate between the optical waveguide substrate and the holding substrate become small in different axial directions on a joint surface.

Apparatus, circuits and methods for reducing mismatch in an electro-optic modulator are described herein. In some embodiments, a described optical includes: a splitter configured for splitting an input optical signal into a first optical signal and a second optical signal; a phase shifter coupled to the splitter; and a combiner coupled to the phase shifter. The phase shifter includes: a first waveguide arm configured for controlling a first phase of the first optical signal to generate a first phase-controlled optical signal, and a second waveguide arm configured for controlling a second phase of the second optical signal to generate a second phase-controlled optical signal. Each of the first and second waveguide arms includes: a plurality of straight segments and a plurality of curved segments. The combiner is configured for combining the first and second phase-controlled optical signals to generate an output optical signal.

A method of fabricating an electro-optical device is provided. The method comprises providing a silicon-on-insulator (SOI) wafer comprising a silicon layer, a silicon oxide layer and at least one RF (radio frequency) electrode, wherein the at least one RF electrode is arranged inside the upper portion of the silicon oxide layer of the SOI wafer and providing a second substrate having a top structure of a RF (radio frequency) modulating material. The method further comprises bonding the second substrate on top of the SOI wafer such that said top structure of a RF (radio frequency) modulating material is arranged over the at least one RF electrode. Also, an electro-optical device is provided.

An electro-optic modulator comprises a resonator comprising a first waveguide having a first end and second end; a first grating at the first end; and a second grating at the second end. An input channel is in communication with the resonator, and comprises a second waveguide having a first end and second end; an input port at the first end; a third grating at the second end; and a first coupler configured to couple light between the second waveguide and the first waveguide. An output channel is in communication with the resonator, and comprises a third waveguide having a first end and second end; an all-pass filter at the first end; a readout port at the second end; and a second coupler configured to couple light between the first and third waveguides. The all-pass filter is configured to adjust a coupling strength between the second coupler and the readout port.

Various embodiments of a monolithic electro-optical (E-O) modulator are described. The monolithic E-O modulator includes an active region comprising a plurality of p-n junction diodes, as well as a modulation electrode and a bias electrode that extend through the active region. The monolithic E-O modulator further includes a resistor-capacitor-bias-capacitor (RCBC) electrode structure configured to receive an electrical modulation signal, a direct-current (DC) bias voltage and a power supply voltage. Specifically, the RCBC electrode structure includes a resistor coupled to the modulation electrode and two capacitors each coupled to a respective end of the bias electrode. Beneficially, the RCBC electrode structure enables the p-n junction diodes to be biased independently from a DC level of the electrical modulation signal.

An optical modulator includes an optical modulation element having a plurality of signal electrodes; a housing that houses the optical modulation element; a plurality of signal input terminals each of which inputs an electrical signal to be applied to each of the signal electrodes; and a relay substrate on which a plurality of signal conductor patterns that electrically connect each of the signal input terminals to each of the signal electrodes, and a plurality of ground conductor patterns are formed, in which the relay substrate is housed in the housing, and at least one input side ground conductor pattern extending from at least one of the ground conductor patterns is formed on an input side surface having a side on which an electrical signal output from the signal input terminal is input to the signal conductor pattern as one side.

An optical transmitter includes a bias supplying unit configured to supply a first bias voltage, a second bias voltage and a third bias voltage to an optical modulator. The bias supplying unit acquires a first voltage value at which an average value of an optical output signal becomes maximum by sweeping the first bias voltage, acquires a second voltage value at which an average value of the optical output signal becomes maximum by sweeping the second bias voltage, and acquires a third voltage value at which an average value of the optical output signal becomes maximum by sweeping the third bias voltage. The bias supplying unit determines a value of the first bias voltage based on the first voltage value, determines a value of the second bias voltage based on the second voltage value, and determines a value of the third bias voltage based on the third voltage value.

An optical waveguide element including a substrate, an optical waveguide formed on the substrate, and an electrode for controlling a light wave propagating through the optical waveguide, in which the optical waveguide and the electrode have an intersection in which the optical waveguide and the electrode intersect with each other, and at the intersection, the electrode has a multilayer structure including a plurality of metal layers made of a metal material, and a resin layer made of a resin material is formed between the electrode and the substrate.

The performance of an electro-optic modulator depends in part on the capacitance, the inductance, the electric field distribution, and the signal insertion loss of a microwave transmission line that modulates the refractive index of a waveguide via the electro-optic effect. Conventional electro-optic modulators are typically unable to improve one of these properties without negatively affecting other properties, resulting in lower performance. These shortcomings may be overcome, in part, by the inclusion of capacitive structures to decouple these properties. The capacitive structure may include a fang and/or a hook to tune the capacitance and the electric field distribution without appreciably changing the inductance or the signal insertion losses. The inductance and the signal insertion losses may be tuned by changing the sizes and shapes of a signal conductor, a ground conductor, and a slot formed between the signal and ground conductors without appreciably changing the capacitance or the electric field distribution.