Methods and apparatuses for downconverting are provided. A dual-drive mach zehnder modulator (DDMZM) receives: a continuous wavelength optical signal, an input signal (microwave signal), and local oscillator tones. The DDMZM includes: first and second arms formed from optical waveguides which receive the optical signal, a first modulator that receives the input signal, and a second modulator that receives the oscillator tones. The input signal is modulated onto the optical signal propagating through the first arm to form a first modulated optical signal. The oscillator tones and third-order intermodulation products of those tones are modulated onto the optical signal propagating through the second arm to form a second modulated optical signal. The modulated optical signals are combined to form an output optical signal. The oscillator tones are spaced two folded bandwidths apart and centered within a spectrum of interest of the input signal.

Various embodiments of a coplanar waveguide (CPW) transmission line as well as a silicon-based electro-optic (E-O) modulator comprising the CPW transmission line are described. The CPW transmission line has a curved or winding shape. The silicon-based E-O modulator includes a rib optical waveguide, a beam splitter, a beam combiner, and a CPW transmission line that exhibits the winding shape. At least one of the two optical arms of the rib optical waveguide alternately and periodically extends through a first groove and a second groove of the CPW transmission line. The plurality of active sections of the rib optical waveguide are evenly distributed on both sides of the CPW transmission line to suppress undesired transmission modes. An increased length of transmission path of the rib optical waveguide is also avoided or minimized, thereby reducing the transmission speed mismatch of the E-O modulator, which is essential for achieving high-speed operation.

An optical transmitter includes a Mach-Zehnder modulator having an arm waveguide and a phase controller configured to control a phase of a light propagating through the arm waveguide by applying a voltage to the Mach-Zehnder modulator. When the voltage is deviated from a predetermined range, the phase controller shifts the voltage in the direction opposite to a direction of the deviation from the predetermined range by the amount corresponding to a change of 2π in the phase.

An optical transmitter includes an electro-optic modulator, a monitor circuit that monitors output light of the electro-optic modulator, and a processor that controls a bias voltage of the electro-optic modulator using a monitoring result of the monitor circuit, wherein the processor superimposes a first dither signal with a first frequency and a second dither signal with a second frequency different from the first frequency, onto one bias voltage in a time sharing manner, calculates a first control error based on a first component oscillating at the first frequency and a second control error based on a second component oscillating at the second frequency based on the monitoring result, and determines a control value for controlling the bias voltage using the first control error and the second control error.

An electro-optic modulator for a waveguide is presented. The electro-optic modulator includes a first semiconductor layer, a second semiconductor layer, a dielectric layer interposed between the second semiconductor layer and the first semiconductor layer and a coupling layer for coupling a guided mode of the waveguide to at least one of the first semiconductor layer and the second semiconductor layer. The electro-optic modulator is configured to induce a modulation on the guided mode of the waveguide by changing a refractive index in response to a voltage applied between the first semiconductor layer and the second semiconductor layer.

A coplanar waveguide wire electrode structure and a modulator includes a metal electrode and an optical waveguide. The metal electrode includes ground electrodes and a signal electrode. Connecting arms are arranged on both sides of the signal electrode. The inner sides of the ground electrodes are provided with other connecting arms. The tail ends of the connecting arms of the signal electrode are provided with signal wire extension electrodes, and the tail ends of the connecting arms of the ground electrodes are provided with ground wire extension electrodes. A distance is provided between the signal wire extension electrodes and the ground wire extension electrodes. The optical waveguide passes through the spaces between the signal wire extension electrodes and the ground wire extension electrodes. By extending the metal electrode, the distance between the electrodes is actually shortened.

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 includes a slot groove formed in a substrate; a pair of electrodes disposed in the slot groove; an electro-optic polymer material in the slot groove; and a step portion formed at an outer side of the slot groove, in a length direction of the slot groove.

An optical modulator includes an optical waveguide through which signal light passes, a split unit that splits the signal light that passes through the optical waveguide, and a pair of phase shifters each of which shifts a phase of signal light that is split by the split unit. Each of the phase shifters includes an in-shifter waveguide through which the signal light passes, and a heater electrode that heats the in-shifter waveguide in accordance with a driving voltage. The in-shifter waveguide includes an inbound waveguide for inputting the signal light coming from the split unit, an outbound waveguide for outputting the signal light, a folded waveguide that connects the inbound waveguide and the outbound waveguide. The heater electrode is arranged in the vicinity of the inbound waveguide and the outbound waveguide.

Disclosed are a Mach-Zehnder interferometric optical modulator and a method for manufacturing the same. The modulator includes first and second lower clad layers, a core layer, an upper clad layer, a waveguide, and electrodes. The waveguide may include an input waveguide, a waveguide divider, branch waveguides, and a waveguide combiner. Each of the branch waveguides includes first and second connection regions connected to the waveguide combiner and the waveguide divider, respectively, and a phase shift region having a cross-section of a reverse mesa structure that has an upper width that is the same as widths of the first and second connection regions and a lower width that is smaller than the widths of the first and second connection regions.