An optical coupling may involve orienting a waveguide and a lens such that light rays are focused on a surface. The lens may involve the use of a material having a variable refractive index to focus rays of light along first axis and a curved surface to focus the rays of light along a second axis.

To make connection work be done easily and certainly, and, further, space-saving be achieved, when an optical fiber and an optical module are connected. An optical module includes a connecting face connected with an optical connector and a first diffraction grating, provided in an end part of a first optical waveguide, to convert an optical axis direction of the first optical waveguide to a direction toward an opposing face of the optical connector; in the optical connector, the second optical waveguide is provided in the optical connector along the opposing face toward the connecting face; the optical connector includes a second diffraction grating, provided in an end part of the second optical waveguide, to convert an optical axis direction of the second optical waveguide into a direction toward the optical module; and while the optical module and the optical connector are connected mechanically to make the opposing face of the optical connector oppose the connecting face of the optical module, the first diffraction grating and the second diffraction grating opposing each other and being coupled optically.

To make connection work be done easily and certainly, and, further, space-saving be achieved, when an optical fiber and an optical module are connected. An optical module includes a connecting face connected with an optical connector and a first diffraction grating, provided in an end part of a first optical waveguide, to convert an optical axis direction of the first optical waveguide to a direction toward an opposing face of the optical connector; in the optical connector, the second optical waveguide is provided in the optical connector along the opposing face toward the connecting face; the optical connector includes a second diffraction grating, provided in an end part of the second optical waveguide, to convert an optical axis direction of the second optical waveguide into a direction toward the optical module; and while the optical module and the optical connector are connected mechanically to make the opposing face of the optical connector oppose the connecting face of the optical module, the first diffraction grating and the second diffraction grating opposing each other and being coupled optically.

System and method embodiments are provided for optical I/O arrays for wafer scale testing. A wafer includes a plurality of dies of PIC chips. Each die includes a plurality of first and second optical I/O elements each configured to couple to a testing probe array. A row of I/O elements includes alternating ones of the first and second optical I/O elements. Each die also includes a first waveguide and a second waveguide coupling a first one of the first and second optical I/O elements to a second one of the first and second optical I/O elements, respectively. The first and second optical I/O elements configured such that the testing probe array couples to at least some of the first optical I/O elements from a first side of the PIC chip and couples to at least some of the second optical I/O elements from a second side of the PIC chip.

System and method embodiments are provided for optical I/O arrays for wafer scale testing. A wafer includes a plurality of dies of PIC chips. Each die includes a plurality of first and second optical I/O elements each configured to couple to a testing probe array. A row of I/O elements includes alternating ones of the first and second optical I/O elements. Each die also includes a first waveguide and a second waveguide coupling a first one of the first and second optical I/O elements to a second one of the first and second optical I/O elements, respectively. The first and second optical I/O elements configured such that the testing probe array couples to at least some of the first optical I/O elements from a first side of the PIC chip and couples to at least some of the second optical I/O elements from a second side of the PIC chip.

A light flux diameter expanding element includes a light guiding plate with a light input face and a light output face, and with a thickness of 0.2 mm to 0.8 mm; a diffraction grating on the input side; and a diffraction grating on the output side, and is provided so as to have the same grating period as that of the diffraction grating on the input side, in which a forming region of the diffraction grating on the input side is smaller than that of the output side, and a grating period of the diffraction grating on the input side is a period in which a small diffraction angle in diffraction angles of +1-st order diffracted light and −1-st order diffracted light, which are diffracted in the diffraction grating on the input side, in the light guiding plate becomes larger than a critical angle of the light guiding plate.

A light flux diameter expanding element includes a light guiding plate with a light input face and a light output face, and with a thickness of 0.2 mm to 0.8 mm; a diffraction grating on the input side; and a diffraction grating on the output side, and is provided so as to have the same grating period as that of the diffraction grating on the input side, in which a forming region of the diffraction grating on the input side is smaller than that of the output side, and a grating period of the diffraction grating on the input side is a period in which a small diffraction angle in diffraction angles of +1-st order diffracted light and −1-st order diffracted light, which are diffracted in the diffraction grating on the input side, in the light guiding plate becomes larger than a critical angle of the light guiding plate.

A photonic integrated circuit comprises an input interface adapted for receiving an optical input signal and splitting it into two distinct polarization modes and furthermore adapted for rotating the polarization of one of the modes for providing the splitted signals in a common polarization mode. The PIC also comprises a combiner adapted for combining the first mode signal and the second mode signal into a combined signal and a decohering means adapted for transforming at least one of the first mode signal and the second mode signal such that the first mode signal and the second mode signal are received by the combiner in a mutually incoherent state. A processing component for receiving and processing said combined signal is also comprised.

A photonic integrated circuit comprises an input interface adapted for receiving an optical input signal and splitting it into two distinct polarization modes and furthermore adapted for rotating the polarization of one of the modes for providing the splitted signals in a common polarization mode. The PIC also comprises a combiner adapted for combining the first mode signal and the second mode signal into a combined signal and a decohering means adapted for transforming at least one of the first mode signal and the second mode signal such that the first mode signal and the second mode signal are received by the combiner in a mutually incoherent state. A processing component for receiving and processing said combined signal is also comprised.

A semiconductor device includes a substrate, a trench in the substrate, the trench having an inclined sidewall, a reflective layer over the inclined sidewall, a grating structure over the substrate, and a waveguide in the trench. The waveguide is configured to guide optical signals between the grating structure and the reflective layer.