In order to provides an optical waveguide element and an optical modulator that can prevent the damage to the substrate and the deterioration of the properties of the substrate that may occur due to the stress, by reducing the influence of stress on the substrate by the buffer layer, the optical waveguide 1 is provided with a substrate 5 having an electro-optical effect; an optical waveguide 10 formed on the substrate 5; a first buffer layer 9a provided on the substrate 5; and a second buffer layer 9b provided under the substrate 5, wherein the first buffer layer 9a and the second buffer layer 9b are composed of substantially the same material and have substantially the same thickness, and the first buffer layer 9a and the second buffer layer 9b are formed to be in contact with an upper surface and lower surface of the substrate 5, respectively.

An optical phase shift circuit can include: a first Mach Zehnder lattice and a second Mach Zehnder lattice. Each Mach Zehnder lattice can have a first waveguide and a second waveguide, with a set of active phase shifters disposed along one of the waveguides and a plurality of directional coupler regions disposed along both waveguides between the active phase shifters. A first passive phase shifter can be coupled between one output path of the first Mach Zehnder lattice and one input path of the second Mach Zehnder lattice, and a second passive phase shifter can be coupled between the other output path of the first Mach Zehnder lattice and the other input path of the second Mach Zehnder lattice. Optical phase shift circuits of this kind can be used to implement phase shifters in a Generalized Mach Zehnder interferometer.

This optical modulator includes an optical modulation element having a first optical waveguide, a second optical waveguide, a first electrode configured to apply an electric field to the first optical waveguide, and a second electrode configured to apply an electric field to the second optical waveguide; and a control unit configured to control an applied voltage between the first electrode and the second electrode. The control unit sets Vpp to 0.06×Vπ≤Vpp≤0.4×Vπ when a half-wavelength voltage of the optical modulation element is Vπ and an applied voltage width that is an amplitude of an applied voltage applied to the optical modulation element is Vpp, and sets Vn≤Vmin≤Vn+0.29×Vπ or Vn−0.29×Vπ≤Vmax≤Vn when a minimum value and a maximum value of a voltage applied to the optical modulation element are respectively Vmin and Vmax and a null point voltage of the optical modulation element is Vn.

A light source unit (1000) of the present disclosure includes a light source part (100), a first electrical signal generating device (40-1) configured to control current that drives an optical semiconductor device (30), an optical modulator (200) having a Mach-Zehnder type optical waveguide (10) and an electrode configured to apply an electric field to the optical waveguide (10), and a second electrical signal generating device (40-2) configured to control a voltage that operates the optical modulator (200), the first electrical signal generating device (40-1) and the second electrical signal generating device (40-2) are synchronizably connected to each other, and intensity of light emitted from the optical modulator (200) is changed by the current controlled by the first electrical signal generating device (40-1) and the voltage controlled by the second electrical signal generating device (40-2).

Provided is an optical phase shifter. The optical phase shifter includes: a slab waveguide in which a first slab region doped into a first conductivity type and a second slab region doped into a second conductivity type are arranged side by side to form a PN junction; and a rib waveguide disposed on the slab waveguide such that one side of the rib waveguide makes contact with the first slab region, and an opposite side of the rib waveguide makes contact with the second slab region, wherein the rib waveguide includes first to third rib waveguide layers that are sequentially stacked, the first and third rib waveguide layers include silicon (Si), and the second rib waveguide layer includes silicon-germanium (SiGe).

Provided is an optical phase shifter. The optical phase shifter includes: a silicon substrate; a cladding layer disposed on the silicon substrate; an intermediate film disposed on the cladding layer; a KTN (KTaNbO.sub.3) waveguide disposed on the intermediate film; a protective layer disposed on the intermediate film to cover the KTN waveguide; and first and second electrodes disposed on the intermediate film while being spaced apart from each other with the KTN waveguide interposed between the first and second electrodes, wherein a silicon waveguide is disposed inside the cladding layer while being spaced apart from the KTN waveguide with the intermediate film interposed between the silicon waveguide and the KTN waveguide.

A generator device for generating an arbitrary optical pulse pattern includes: a light source to provide primary laser pulses, a distributor to provide a plurality of primary optical pulses by distributing light of the primary laser pulses (LB00.sub.k) into a plurality of branches, a combiner to form an output signal by combining modulated optical signals from the branches, and a controller unit to provide control signals for controlling optical modulators of the branches, wherein a first branch comprises a first optical modulator to form a first modulated optical signal from primary optical pulses of the first branch, wherein a second branch comprises a second optical modulator to form a second modulated optical signal from primary optical pulses of the second branch, and wherein a propagation delay of the second branch is different from a propagation delay of the first branch.

Provided are an optical modulating device and a system including the optical modulating device. The optical modulating device includes a substrate, and a phase modulator formed on the substrate and including a Fabry-Perot cavity. The Fabry-Perot cavity of the phase modulator includes a first reflective layer, a second reflective layer, and a tunable core formed between the first reflective layer and the second reflective layer, wherein the tunable core is formed of a semiconductor material and is configured to modulate a phase of light corresponding to modulation of a refractive index of the tunable core according to electrical control.

Provided are an optical modulating device and a system including the optical modulating device. The optical modulating device includes a substrate, and a phase modulator formed on the substrate and including a Fabry-Perot cavity. The Fabry-Perot cavity of the phase modulator includes a first reflective layer, a second reflective layer, and a tunable core formed between the first reflective layer and the second reflective layer, wherein the tunable core is formed of a semiconductor material and is configured to modulate a phase of light corresponding to modulation of a refractive index of the tunable core according to electrical control.

Embodiments are disclosed for generating an optical Pulse Amplitude Modulation 4-level (PAM-4) signal from bandwidth-limited duobinary electrical signals in a Mach-Zehnder modulator. An example system includes an MZM structure that comprises a first waveguide interferometer arm structure associated with a first semiconductor device and a second waveguide interferometer arm structure associated with a second semiconductor device. A polybinary electrical signal is applied to or between the first semiconductor device and the second semiconductor device to convert an input optical signal provided to the MZM structure into an optical PAM-4 signal.