With a wavelength conversion device based on a nonlinear optical effect, when arrayed waveguides including an intended nonlinear waveguide are fabricated, unwanted slab waveguides are inevitably formed. The slab waveguides can cause an erroneous measurement in the selection of a waveguide having desired characteristics from the arrayed waveguides. The erroneous measurement can lead to redoing steps for fabricating the wavelength conversion device and a decrease in the yield and inhibit the evaluation of the characteristics in selection of the waveguide and the subsequent fabrication of the wavelength conversion device from being efficiently performed. A wavelength conversion device according to the present invention includes a plurality of waveguides formed on a substrate, and a plurality of slab waveguides that are arranged substantially in parallel with and spaced apart from the plurality of waveguides, and each of the slab waveguides has a grating structure that reflects light of a particular wavelength.

An optical modulator includes: first and second optical waveguides formed of an electro-optic material film on a substrate so as to have a ridge shape and to be disposed adjacent to each other; a buffer layer covering at least the upper surfaces of the first and second optical waveguides; and first and second signal electrodes provided above the buffer layer. The first and second signal electrodes have, respectively, first and second lower layer parts opposite, respectively, to the first and second optical waveguides through the buffer layer; and first and second upper layer parts provided, respectively, above the first and second lower layer parts. Widths of the lower surfaces of the first and second lower layer parts are smaller than widths of the first and second upper layer parts.

Reduction of output power of light with a wavelength converted is suppressed, which is caused by a pyroelectric effect that occurs when a temperature of a wavelength conversion element including a ferroelectric substrate is changed. Provided is a wavelength conversion device that generates light different from a wavelength of a signal light when the signal light is inputted, and includes a wavelength conversion element that converts a wavelength of the signal light, and a temperature control element for controlling a temperature of the wavelength conversion element, wherein the wavelength conversion element and the temperature control element are sealed in an inside of a metal casing, the wavelength conversion element includes an optical waveguide core and a substrate having a lower refractive index to the signal light than the optical waveguide core, and the substrate is a ferroelectric substance in which directions of spontaneous polarization are random.

A fiber-to-fiber system for multi-layer ferroelectric on insulator waveguide devices is described. The system comprises a fiber-to-chip coupler that couples light from a standard optical fiber to multi-layer ferroelectric on insulator waveguides. The multi-layer ferroelectric on insulator waveguides are integrated with electrodes to implement an optical device, an electro-optical device, or a non-linear optical device, such as an electro-optical modulator, with microwave and optical waveguide crossings compatible with packaging. A second fiber-to-chip coupler outputs the light from the multi-layer ferroelectric on insulator device to a standard optical fiber.

An active optical modulator receives a radio frequency signal and provides an intensity modulated optical signal. The optical modulator is formed on a substrate having a doped region. An interferometer is formed on the substrate having a first path and a second path. A low noise amplifier receives the radio frequency signal and provides an electrical field to the paths. A signal laser provides an optical signal to the interferometer which is modulated and interfered to produce an intensity modulated optical signal. A pump laser provides an optical gain signal to the interferometer where it adds gain to the optical signal in the interferometer by interaction with the doped region of the substrate.

An optical modulator, including: a substrate; a plurality of electro-optic material layers formed on the substrate; and an electrode formed on the electro-optic material layer; wherein the electro-optic material layer has a patterned RF portion waveguide that applies a modulated signal and a patterned DC portion waveguide that applies a direct current bias signal; and on a section perpendicular to a light propagation direction, the sectional area of the DC portion waveguide is greater than the sectional area of the RF portion waveguide.

It is possible to provide an optical modulator in which a transmission loss from a driver circuit element to a modulation substrate is reduced. An optical modulator includes a modulation substrate (1) that includes an optical waveguide (200) and a modulation electrode (10) for modulating a light wave propagating through the optical waveguide, a driver circuit element (2) that generates a modulation signal to be applied to the modulation electrode (10), and a case (3) that accommodates the modulation substrate (1) and the driver circuit element (2), in which an output terminal (20′) that outputs the modulation signal is provided on an upper surface side of the driver circuit element (2), and a wiring substrate (4) including a wiring that electrically connects the output terminal (20′) and the modulation electrode (10) is disposed above the driver circuit element (2) and the modulation substrate (1) to straddle both the driver circuit element (2) and the modulation substrate (1).

An optical device, including a substrate; an optical waveguide provided in a predetermined region of the substrate and formed of an electro-optic material film; a protective layer formed adjacent to the optical waveguide; and a non-light-propagation optical waveguide provided outside the predetermined region, wherein the surface roughness of the non-light-propagation optical waveguide is RMS 0.5 nm or more. According to the optical device, the occurrence of micro-cracks on the optical waveguide can be suppressed, thereby reducing the light propagation loss.

A cavity-enhanced frequency mixer includes an input optical fiber, a waveguide, and an output optical fiber. The waveguide has an input end and an output end, the input end is connected to the input optical fiber, and a surface of the input end of the waveguide is coated with a highly reflective coating. The output optical fiber is formed with a fiber Bragg grating structure. The highly reflective coating and the fiber Bragg grating structure form a pair of reflective surfaces for resonant optical parametric oscillation under a low threshold situation, so that one of the beams generated by the input beam is reflected inside the partially reflective surfaces. Operated above a pump power threshold, the cavity-enhanced frequency mixer is tantamount to a compact, low-power budget optical parametric oscillator, while below the pump power threshold, it is a bright, compact, single-mode and narrow linewidth single-photon source.

A periodically poled microring resonator structure, a method for fabrication of the periodically poled microring resonator structure, and a method to achieve giant single-photon nonlinearity are disclosed. The strong single-photon nonlinearity in the microring resonator structure is achieved through its optimized design and fabrication procedures.