Improved dither detection, measurement, and voltage bias adjustments for an electro-optical modulator are described. The electro-optical modulator generally includes RF electrodes and phase heaters interfaced with semi-conductor waveguides on the arms of Mach-Zehnder interferometers, where a processor is connected to output a bias tuning voltage to the electro-optical modulator for controlling optical modulation. A variable gain amplifier (VGA) can be configured with AC coupling connected to receive a signal from a transimpediance amplifier (TIA) that is configured to amply a photodetector signal from an optical tap that is used to measure an optical signal with a dither signal. The analog to digital converter (ADC) can be connected to receive output from the VGA. The processor can be connected to receive the signal from the ADC and to output the bias tuning voltage based on evaluation of the signal from the tap.

The present invention discloses a directional photonic coupler (1) with independent tuning of the coupling factor and phase difference. The coupler comprises: two waveguides (4, 5), with respective propagation constants “β.sub.1, β.sub.2”, on which phase shifters (6, 7) configured to modify the propagation coefficients are located. Both phase shifters are configured such that, by independent modification (differential or unique) of the propagation coefficients, the power coupling factor (K) between an input signal (2a or 2b) and the output signals (3b and 3a) is tuned, and by equal and simultaneous modification of the propagation coefficients, the common phase difference of the optical output signals (3 a, 3b) is tuned. A third phase shifter (15) can be used to retune the phase difference at the input/output of one of the waveguides. The coupler is of particular interest in PIC circuits, coupled resonators, Mach-Zehnder interferometers and mesh structures.

The present invention discloses a directional photonic coupler (1) with independent tuning of the coupling factor and phase difference. The coupler comprises: two waveguides (4, 5), with respective propagation constants “β.sub.1, β.sub.2”, on which phase shifters (6, 7) configured to modify the propagation coefficients are located. Both phase shifters are configured such that, by independent modification (differential or unique) of the propagation coefficients, the power coupling factor (K) between an input signal (2a or 2b) and the output signals (3b and 3a) is tuned, and by equal and simultaneous modification of the propagation coefficients, the common phase difference of the optical output signals (3 a, 3b) is tuned. A third phase shifter (15) can be used to retune the phase difference at the input/output of one of the waveguides. The coupler is of particular interest in PIC circuits, coupled resonators, Mach-Zehnder interferometers and mesh structures.

An optical modulator includes a plurality of optical modulation units having a Mach-Zehnder type optical waveguide consisting of two optical waveguides and a high-frequency line pair arranged along the two optical waveguides and consisting of two signal electrodes for applying a pair of differential high-frequency signals, and a plurality of high-resistance conductive films are provided between adjacent high-frequency line pairs separated from the high-frequency line pair.

A waveguide structure for use in a balanced push-pull Mach Zehnder modulator. The waveguide structure comprises a plurality of layers. The layers comprise, in order: an insulating or semi-insulating substrate; an lower cladding layer; an waveguide core layer; and an upper cladding layer. The lower cladding layer, waveguide core layer, and upper cladding layer are etched to form: a signal waveguide and a ground waveguide, which are connected via the lower cladding layer; and a signal line and a ground line, each located adjacent to the respective waveguide, and each connected to the respective waveguide via one or more respective resistive structures connected in the plane of the lower cladding layer.

A photonic integrated circuit device includes a semiconductor substrate (e.g., wafer) having a chip region therein, which is bounded on at least one side thereof by a scribe line. The chip region includes an optical transmitter, an optical receiver and a test optical waveguide. This test optical waveguide is coupled to the optical transmitter and the optical receiver and overlaps the scribe line. During a substrate dicing operation, a portion of the test optical waveguide overlapping the scribe line is removed.

A monolithic integrated electro-optical phase modulator, a Mach-Zehnder modulator including one or more of the phase modulators, and method for fabricating the phase modulator by III-V-on-silicon semiconductor processing are provided. The phase modulator includes a silicon-based n-type substrate base layer, and a III-V n-type ridge waveguide for propagating light, wherein the ridge waveguide protrudes from and extends along the n-type substrate base layer. Further, the phase modulator includes one or more insulating layers provided on the ridge waveguide, wherein the one or more insulating layers have together a thickness of 1-100 nm, and a silicon-based p-type top cover layer provided on the one or more insulating layers at least above the ridge waveguide.

An optical phase modulator includes a lower cladding layer, a core formed on the lower cladding layer, an upper cladding layer formed over the core, and a heater. In addition, the optical phase modulator includes a semiconductor layer which is embedded in the upper cladding layer, is disposed above the core, and is formed of a compound semiconductor, and the heater is constituted by an impurity introduction region formed in the semiconductor layer.

To effectively prevent the acceleration of the drift phenomenon generated by the application of a high electric field to a substrate through a bias electrode in a waveguide type optical element. A waveguide type optical element includes a substrate (100) having an electro-optic effect, two optical waveguides (104 and 106) disposed on a surface of the substrate, a non-conductive layer (120) which is disposed on the substrate and is made of a material having a lower dielectric constant than the substrate, and a control electrode (150) which is disposed on the non-conductive layer and is intended to generate a refractive index difference between the two optical waveguides by respectively applying electric fields to the two optical waveguides, and the non-conductive layer is constituted of a material which includes silicon oxide, an oxide of indium, and an oxide of titanium and has a ratio between a molar concentration of the titanium oxide and a molar concentration of indium oxide of 1.2 or more, and a voltage generating an electric field of 1 V/μm or more in the substrate is applied to the control electrode.

To effectively prevent the acceleration of the drift phenomenon generated by the application of a high electric field to a substrate through a bias electrode in a waveguide type optical element. A waveguide type optical element includes a substrate (100) having an electro-optic effect, two optical waveguides (104 and 106) disposed on a surface of the substrate, a non-conductive layer (120) which is disposed on the substrate and is made of a material having a lower dielectric constant than the substrate, and a control electrode (150) which is disposed on the non-conductive layer and is intended to generate a refractive index difference between the two optical waveguides by respectively applying electric fields to the two optical waveguides, and the non-conductive layer is constituted of a material which includes silicon oxide, an oxide of indium, and an oxide of titanium and has a ratio between a molar concentration of the titanium oxide and a molar concentration of indium oxide of 1.2 or more, and a voltage generating an electric field of 1 V/μm or more in the substrate is applied to the control electrode.