A multi-level semiconductor device, the device including: a first level including integrated circuits; a second level including a structure designed to conduct electromagnetic waves, where the second level is disposed above the first level, where the integrated circuits include single crystal transistors; and an oxide layer disposed between the first level and the second level, where the integrated circuits include at least one processor, where the second level is bonded to the oxide layer, and where the bonded includes oxide to oxide bonds.

A method for forming at least one freestanding microstructure on a diamond crystal includes the step of removing material from the diamond crystal so as to form a structured surface, wherein the removing of the material includes creating at least two trenches, each trench having a bottom and two side walls and wherein adjacent side walls of the at least two trenches form side walls of the structured surface. The method also includes the steps of depositing at least one masking layer on the structured surface, removing at least a portion of the at least one masking layer from the bottom of each of the at least two trenches, removing additional material from the diamond crystal at least along the side walls so as to deepen the trenches, and undercutting the diamond crystal so as to form the freestanding microstructure.

A method for forming at least one freestanding microstructure on a diamond crystal includes the step of removing material from the diamond crystal so as to form a structured surface, wherein the removing of the material includes creating at least two trenches, each trench having a bottom and two side walls and wherein adjacent side walls of the at least two trenches form side walls of the structured surface. The method also includes the steps of depositing at least one masking layer on the structured surface, removing at least a portion of the at least one masking layer from the bottom of each of the at least two trenches, removing additional material from the diamond crystal at least along the side walls so as to deepen the trenches, and undercutting the diamond crystal so as to form the freestanding microstructure.

A waveguide includes a core and a cladding. The core has an inlet on which light is incident. The core includes a front portion and a rear portion located between the front portion and the inlet. The front portion and the rear portion each have a thickness that is a dimension in a first direction and a width that is a dimension in a second direction. The first direction is orthogonal to a propagation direction of the light. The second direction is orthogonal to the propagation direction of the light and the first direction. The thickness of the front portion decreases with increasing distance from the inlet.

A process for forming glass planar waveguide structure includes producing or obtaining a fusion drawn glass laminate (10) comprising a core glass layer (10) and a first clad glass layer (14) and a second clad glass layer (16) then removing or thinning portions of at least the second glass clad layer (16) leaving remaining or thicker portions of the second glass clad layer (16), the remaining or thicker portions corresponding to a planar waveguide pattern and resulting in a glass planar waveguide structure.

Provided is an optical modulator manufacturing method capable of determining the quality of an optical modulator having MMI waveguides and realizing improvement in yield during manufacturing. Here, in waveguide fabrication processes, hard mask material deposition, soft mask material application, exposure, and hard mask fabrication are executed, and then in hard mask width length measurement, the hard mask width for fabricating the MMI waveguide is measured at one or more locations. In hard mask width quality determination based on machine learning results, the quality of optical characteristics of the chip is predicted and determined in advance, based on sample data created in advance by analyzing a relationship between the hard mask width and optical characteristics of the optical modulator, depending on whether the hard mask width is present in a permissible range of the sample data. Depending on the result of the above-mentioned determination the mask fabrication is redone.

Provided is an optical modulator manufacturing method capable of determining the quality of an optical modulator having MMI waveguides and realizing improvement in yield during manufacturing. Here, in waveguide fabrication processes, hard mask material deposition, soft mask material application, exposure, and hard mask fabrication are executed, and then in hard mask width length measurement, the hard mask width for fabricating the MMI waveguide is measured at one or more locations. In hard mask width quality determination based on machine learning results, the quality of optical characteristics of the chip is predicted and determined in advance, based on sample data created in advance by analyzing a relationship between the hard mask width and optical characteristics of the optical modulator, depending on whether the hard mask width is present in a permissible range of the sample data. Depending on the result of the above-mentioned determination the mask fabrication is redone.

A waveguide bend which has low loss while keeping the curvature radius small in a waveguide with a given A is realized. An optical waveguide has a straight waveguide and a waveguide bend connected to each other, and tapered waveguide bends inserted between the straight waveguide and the waveguide bend, a curvature radius of the tapered waveguide bend being equal to a curvature radius of the waveguide bend, a waveguide width of the tapered waveguide bend changing continuously from the waveguide width of the straight waveguide at the connection point to the waveguide width of the waveguide bend. A waveguide width of the waveguide bend is larger than a waveguide width of the straight waveguide at a connection point and the tapered waveguide bend and the straight waveguide are connected with an optical axis of the tapered waveguide bend and an optical axis of the straight waveguide being offset.

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.

An optical coupler includes: input-type optical fibers; an output-type optical fiber; and radiant light processing units. The input-type optical fibers are bundled at leading end side to form a fiber bundle portion, and leading end portion of the fiber bundle portion is connected to the output-type optical fiber. In at least either the input-type optical fibers or the output-type optical fiber, a tapered portion is formed in which cross-sectional area is tapered to become narrower in light traveling direction indicating direction from the input-type optical fibers toward the output-type optical fiber. The number of the tapered portion is equal to or greater than two. Each radiant light processing unit is disposed to mutually overlap with one of the tapered portions or away from one of the tapered portions in the light traveling direction, and is disposed on outer periphery of the input-type optical fibers or the output-type optical fiber.