A method and mode conversion waveguide system for converting a mode of a light is provided. The light is sent through a single mode waveguide, wherein the light has a first mode while traveling through single mode waveguide. The light is sent from the single mode waveguide into a multimode interference region having connected to the single mode waveguide. The light is reflected with a cavity within the multimode interference region in a manner that causes the light to propagate away from the single mode waveguide. The light is output from multimode interference region, wherein the light has a second mode.

An optical circuit element capable of preventing stray light propagated through a part including a substrate of the optical circuit element from being emitted to the outside is provided. The optical circuit element has a substrate, an optical waveguide layer that is formed on one surface of the substrate, and a protective layer that is overlaid on the optical waveguide layer. The optical waveguide layer has an optical waveguide configured for light to be propagated therethrough. A groove portion, which reaches to a position deeper than the one surface from a surface of the protective layer toward the substrate, is formed. The optical circuit element further includes a light absorption layer that covers at least a bottom surface and a side surface of the groove portion.

An apparatus such as an optical modulator includes a buried oxide layer is disposed on a substrate. A microring resonator and an optical waveguide are disposed on the buried oxide layer and within a bonded semiconductor layer. The optical waveguide is optically coupled to the microring resonator and inputs a first optical wave into the microring resonator. An oxide layer is deposited on top of the optical waveguide and the microring resonator. A set of electrodes is disposed adjacent to the microring resonator, and in response to an electrical signal, the set of electrodes modulates the first optical wave into a modulated optical wave of transverse magnetic polarization within the microring resonator and outputs the modulated optical wave to the optical waveguide.

A highly-efficient ridge waveguide includes a base substrate of a single-crystal and a core substrate made of a nonlinear optical medium, the base substrate and the core substrate being directly bonded, and includes a thin film layer formed on a surface of the core substrate on the upper side of a periodically polarization-reversed structure, and becomes a wavelength conversion element. A direct bonding method through thermal diffusion is applied to bonding. The core substrate has a ridge structure formed in a light propagating direction and a reversed structure formed by processing this. A surface of the core substrate is ground and a thin film layer is formed on the ground surface. A core formed by digging a core layer of the core substrate in an unbonded state is provided on an upper surface of an undercladding layer of the base substrate in a bonded state. Two side surfaces of the core are in contact with an air layer.

In an integrated optical device, squeezed light is used internally to effectively increase an optical modulation effect. One exemplary device operates by squeezing the light at the input, then sending it through an electro-optic stage where its phase picks up the signal of interest, and finally anti-squeezing it to obtain a displaced coherent state. Thus the displacement is amplified by the level of squeezing that is achieved inside the device and it is thereby less sensitive to loss. Since this device behaves simply as an electro-optic modulator, albeit one with an exponentially enhanced sensitivity, no extra considerations are needed to integrate the modulator into a system. Such devices can be operated as modulators or as sensors, and can make use of optical phase shift effects other than the electro-optic effect.

The invention relates to an optical modulator. The optical modulator comprising: a substrate; an electro-optical material layer formed on a predetermined region of the substrate; a buffer layer formed on the substrate which is provided so as to cover the electro-optical material layer; and an electrode formed on the buffer layer, and the electro-optical material layer has a RF portion optical waveguide which is applied with a modulation signal and is patterned, and a DC portion optical waveguide which is applied with a DC voltage and is patterned, the electrode has an RF portion electrode formed on the buffer layer where the RF portion optical waveguide is located and a DC portion electrode formed on the buffer layer where the DC portion optical waveguide is located, the film thickness of the DC portion electrode is smaller than the film thickness of the RF portion electrode. According to the present invention, an optical modulator which can suppress electrical crosstalk caused by the noise signal generated in the DC portion electrode and can improve high-frequency characteristics and achieve a widening of bandwidth of the optical frequency band in the high-frequency signals propagating in the RF portion electrode is provided.

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.

A thin film optical waveguide includes a silicon-based substrate, a cladding layer arranged on the silicon-based substrate, and an optical waveguide core layer arranged on the silicon-based substrate. The optical waveguide core layer is arranged in the cladding layer, the optical waveguide core layer includes a double-layer optical waveguide dielectric thin film and a thin film material interlayer arranged between the double-layer optical waveguide dielectric thin film, the thin film material interlayer has a two-dimensional lattice sub-wavelength structure, and the effective lattice constant and the duty cycle of the two-dimensional lattice sub-waveguide structure have at least one numerical value in the same propagation direction. The thin film optical waveguide overcomes the limits of technology and materials, achieves a variable effective refractive index in same propagation direction, satisfies complex design and application scenarios, and reduces the difficulty of manufacturing the thin film optical waveguide having a variable effective refractive index.

The present disclosure relates to electro-optic modulators that include caps for optical confinement. One example embodiment includes an electro-optic modulator. The electro-optic modulator includes a first cladding layer. The electro-optic modulator also includes a second cladding layer. In addition, the electro-optic modulator includes a first waveguide. The first waveguide is at least partially encapsulated between the first cladding layer and the second cladding layer. Further, the electro-optic modulator includes a thin-film lithium niobate layer adjacent to the second cladding layer. The thin-film lithium niobate layer is on an opposite side of the second cladding layer from the first waveguide. Additionally, the electro-optic modulator includes a first cap positioned on an opposite side of the thin-film lithium niobate layer from the second cladding layer. The first cap enhances optical confinement within the thin-film lithium niobate layer. Still further, the electro-optic modulator includes a plurality of electrodes.

An optical device including: a substrate; an optical waveguide formed at the substrate; and a protective layer formed adjacent to the optical waveguide, wherein the optical waveguide includes multiple side surfaces that intersect the substrate, at least one side surface of the optical waveguide is provided with a rough surface. According to the optical device of the present invention, the light propagation loss can be reduced.