Abstract: An electro-optical phase modulator, dual polarization modulator applying that modulator and a phase modulation method are disclosed. A waveguide in an electro-optical substrate has at least two electrodes for modulating the waveguide. Each electrode receives a sequential bit of a precoded digital input and forms a shifting line from a first input end through interaction lengths near the waveguide causing modulation, shifted lengths distal from the waveguide for avoiding modulating the waveguide and transitions between these lengths by shifting the electrode away from or towards the waveguide. At least one electrode has a shorter interaction length closer to the input than a longer interaction length of the same electrode. Each electrode's modulation strength is proportional to its total interaction length, which doubles for each electrode, producing well matched S21 electro-optical responses from 10 kHz to 50 GHz, when shifted to account for the doubling.

Abstract: The invention relates to waveguide optical modulators wherein two or more waveguides are modulated with specific modulation strengths using a single straight signal electrode or a single multi-segment signal electrode. Modulation strengths for each of a plurality of waveguides modulated by a single multi-segment electrode are matched over a wide modulation frequency range. Linearized output characteristics with respect to second and third order distortions arc achieved in one aspect of the invention.

Abstract: An electro-optic device is disclosed, in which an RF signal electrode is used as a bias ground electrode. Thus, for Z-cut lithium niobate electro-optic crystals, there is no need to place a buried bias electrode under the RF signal electrode and over the optical waveguide. As a result, both optical and the RF wave propagation losses are reduced. In another embodiment, a buried bias electrode is placed over the optical waveguide between two buffer layers having a different electrical conductivity. The buffer layer underneath the buried bias electrode has a larger electrical conductivity than the buffer layer above the buried bias electrode. The buffer layer underneath the buried bias electrode reduces the optical loss penalty due to the buried bias electrode located above the optical waveguide, while the buffer layer above the bias electrode reduces leakage currents.

Abstract: The invention relates to an optical device including a passive high confinement waveguide, such as of silicon-rich silicon nitride, on an electro-optic substrate, like lithium niobate, optically coupled to a waveguide in the electro-optic substrate. A wide range of electro-optic devices are enabled by this high confinement waveguide structure, including: directional couplers, compact tap couplers, folded electro-optic devices, electro-optic modulators including ring resonators, electro-optic gratings. Further applications enabled by the present invention include hybrid passive planar lightwave circuits (PLC) integrated with electro-optically active waveguides, using the high confinement waveguide as an intermediary waveguide to transfer optical power between the passive and active components.

Abstract: The invention relates to Y-branch waveguide dual optical phase modulators with improved electro-optic (EO) frequency and step responses at frequencies below 1 Hz for use in low-frequency applications such fiber-optic gyroscopes. A Y-branch waveguide structure is formed in an EO substrate, with three or more electrodes used to form a waveguide phase modulator in each of two output waveguide arms. In one embodiment an insulating buffer layer is provided between at least a portion of the electrodes and the substrate for flattening the low-frequency EO response by reducing the modulation efficiency below 1 Hz. In one embodiment each of the waveguide phase modulators includes two ground electrodes extending along both sides of a signal electrode. A top portion of the substrate may be doped to reduce lateral variations of the substrate conductivity in the waveguide and non-waveguide portions thereof between corresponding signal and ground electrodes.

Abstract: An optical phase modulator having a reduced time drift of an electro-optical response is disclosed. An optical waveguide exhibiting the electro-optic effect includes two serially coupled portions having opposite time drifts of magnitudes of their respective electro-optical responses. As a result, a time drift of an overall electro-optical response of the optical phase modulator is lessened.

Abstract: An optical phase modulator having a reduced time drift of an electro-optical response is disclosed. An optical waveguide exhibiting the electro-optic effect includes two serially coupled portions having opposite time drifts of magnitudes of their respective electro-optical responses. As a result, a time drift of an overall electro-optical response of the optical phase modulator is lessened.

Abstract: The invention relates to an optical device including a passive high confinement waveguide, such as of silicon-rich silicon nitride, on an electro-optic substrate, like lithium niobate, optically coupled to a waveguide in the electro-optic substrate. A wide range of electro-optic devices are enabled by this high confinement waveguide structure, including: directional couplers, compact tap couplers, folded electro-optic devices, electro-optic modulators including ring resonators, electro-optic gratings. Further applications enabled by the present invention include hybrid passive planar lightwave circuits (PLC) integrated with electro-optically active waveguides, using the high confinement waveguide as an intermediary waveguide to transfer optical power between the passive and active components.

Abstract: The present invention provides an electro-optic device comprising three or more radio-frequency (RF) signal electrodes, which each include an input segment. The input segments of the three or more RF-signal electrodes are arranged in a fractal pattern followed in an RF-signal transit direction by a parallel-bend pattern. Advantageously, this arrangement allows matching of RF-signal transit times of the input segments and near matching of RF-signal losses of the input segments.

Abstract: A periodically poled optical waveguide comprising a nonlinear optical crystalline material is provided having poled optical domains slanted with respect to direction of propagation of light within the waveguide. Light reflected from slanted poled optical domains does not couple efficiently back into the optical waveguide, which facilitates reduction of backreflection towards a semiconductor laser source coupled to the waveguide. Reduction of backreflections facilitates stable operation of the semiconductor laser source. A method of manufacturing of a periodically poled optical waveguide with slanted poled domains is also provided.

Abstract: An electro-optic device is disclosed, in which an RF signal electrode is used as a bias ground electrode. Thus, for Z-cut lithium niobate electro-optic crystals, there is no need to place a buried bias electrode under the RF signal electrode and over the optical waveguide. As a result, both optical and the RF wave propagation losses are reduced. In another embodiment, a buried bias electrode is placed over the optical waveguide between two buffer layers having a different electrical conductivity. The buffer layer underneath the buried bias electrode has a larger electrical conductivity than the buffer layer above the buried bias electrode. The buffer layer underneath the buried bias electrode reduces the optical loss penalty due to the buried bias electrode located above the optical waveguide, while the buffer layer above the bias electrode reduces leakage currents.

Abstract: The invention relates to waveguide optical modulators wherein two or more waveguides are modulated with specific modulation strengths using a single straight signal electrode or a single multi-segment signal electrode. Modulation strengths for each of a plurality of waveguides modulated by a single multi-segment electrode are matched over a wide modulation frequency range. Linearized output characteristics with respect to second and third order distortions arc achieved in one aspect of the invention.

Abstract: The invention relates to an electro-optic modulator structure containing an additional set of bias electrodes buried within the device for applying bias to set the operating point. Thus the RF electrodes used to modulate incoming optical signals can be operated with zero DC bias, reducing electrode corrosion by galvanic and other effects that can be present in non-hermetic packages. The bias electrodes are at least partially separated from the substrate with a buffer layer, which in one embodiment has a small amount of conductivity. This conductive buffer layer reduces optical loss from the bias electrodes and also reduces DC drift.

Abstract: A Mach-Zehnder (MZ) interferometer modulator structure for fiberoptic telecommunications is disclosed in which drift of the operating point can be monitored with a reduced phase tracking error. One or more components of free-space light radiated into the substrate of the MZ modulator are selectively detected with one or more photodetectors. Suitable summing circuits are described for nulling out undesired photocurrent contributions in the photodetector(s) from on-state and off-state light radiated from the MZ.

Abstract: The present invention provides an electro-optic device comprising three or more radio-frequency (RF) signal electrodes, which each include an input segment. The input segments of the three or more RF-signal electrodes are arranged in a fractal pattern followed in an RF-signal transit direction by a parallel-bend pattern. Advantageously, this arrangement allows matching of RF-signal transit times of the input segments and near matching of RF-signal losses of the input segments.

Abstract: The invention relates to an external optical modulator comprising a Mach-Zehnder having a signal electrode including at least four sections of unequal length to one another positioned over an alternating domain structure in an electrooptic substrate, and including a center section, or center pair of sections disposed asymmetrically between pairs surrounding sections. The surrounding pairs, comprise the two sections adjacent the center section or pair of sections, and each two sections adjacent the previous pair of sections, moving outwardly from the center to the final outermost pair, L1 and LN at the RF input 2 and RF output 4. In each pair, the section lengths are equal, or the section closer to the RF output 4 has a longer length than the section closer to the RF input 2. The surrounding pairs have lengths that decrease from the innermost pair to the outermost pair. For a zero chirp structure, the section lengths are selected to maintain an equivalent length for the inverted and uninverted domain sections.

Abstract: The invention relates to an optical device including a passive high confinement waveguide, such as of silicon-rich silicon nitride, on an electro-optic substrate, like lithium niobate, optically coupled to a waveguide in the electro-optic substrate. A wide range of electro-optic devices are enabled by this high confinement waveguide structure, including: directional couplers, compact tap couplers, folded electro-optic devices, electro-optic modulators including ring resonators, electro-optic gratings. Further applications enabled by the present invention include hybrid passive planar lightwave circuits (PLC) integrated with electro-optically active waveguides, using the high confinement waveguide as an intermediary waveguide to transfer optical power between the passive and active components.

Abstract: A Mach-Zehnder (MZ) interferometer modulator structure for fiberoptic telecommunications is disclosed in which drift of the operating point can be monitored with a reduced phase tracking error. One or more components of free-space light radiated into the substrate of the MZ modulator are selectively detected with one or more photodetectors. Suitable summing circuits are described for nulling out undesired photocurrent contributions in the photodetector(s) from on-state and off-state light radiated from the MZ.

Abstract: The invention relates to an electro-optic modulator structure containing an additional set of bias electrodes buried within the device for applying bias to set the operating point. Thus the RF electrodes used to modulate incoming optical signals can be operated with zero DC bias, reducing electrode corrosion by electro-migration and other effects that can be present in non-hermetic packages. The bias electrodes include an upper split portion and an optically transparent lower portion. The optically transparent lower layer improves modulation frequency and reduces optical loss.

Abstract: The invention relates to an electro-optic directional coupler suitable for use as a variable optical attenuator at reduced voltages compared to those known in the prior art. The present invention has found that by careful selection of an asymmetric directional coupler geometry, the transfer function of the device can be shifted so that it has an operating point between maximum and minimum transmission. Signal electrodes driven in push pull configuration advantageously use this operating point to achieve significant reduction in operating voltages for switching to maximum or minimum transmission. Asymmetry is created in the directional coupler by forming the waveguides to have different propagation constants by a difference in waveguide width, depth, index of refraction or index profile.