The disclosure describes vacuum cell assemblies that integrate a vacuum envelope with a photonic integrated circuit (PIC). Walls of the vacuum envelope are coupled to the PIC, such as through anodic bonding, so that the PIC forms at least one wall of the vacuum envelope and provides an optically accessible medium and surface for transmitting and distributing light into various cavities of the vacuum envelope through one or more nonplanar waveguides. A surface of the PIC may include a material that is compatible with a material of the walls of the vacuum envelope, such as a silicon-based vacuum envelope bonded to a silicon nitride or amorphous silicon surface of the PIC. Each waveguide may include a bridge structure that forms a planar surface for tightly bonding with the vacuum envelope and preserves properties of the transmitted light between opposing sections of the waveguide.

An embodiment is an optical connection element including a first waveguide core and a second waveguide core on a substrate, the first waveguide core and the second waveguide core configured to propagate a signal light and a resin-curing light, and a mode field conversion portion provided at one end of the first waveguide core, wherein the second waveguide core covers at least the mode field conversion portion on the substrate, and a refractive index of the first waveguide core is higher than a refractive index of the second waveguide core.

An integrated waveguide polarizer comprising: a plurality of silicon layers and a plurality of silicon-nitride layers; each of the plurality of silicon layers and each of the plurality of silicon-nitride layers having a first end and an opposite second end, the first end having a wide width and the second end having a narrow width, such that each silicon layer and each silicon-nitride layer have tapered shapes; wherein the pluralities of silicon and silicon-nitride layers are overlapped, such that at least a portion of each silicon-nitride layer overlaps at least a portion of each silicon layer; and a plurality of oxide layers disposed between the pluralities of silicon-nitride and silicon layers, each oxide layer creating a separation spacing between each silicon-nitride and each silicon layers; wherein, when an optical signal is launched through the integrated waveguide polarizer, the optical signal is transitioned between each silicon-nitride layer and each silicon layer.

A device for combining several light beams, the device including several hollow input waveguides, at least one per light beam, as well as a hollow output waveguide which is the same for the different light beams, each input waveguide having an input opening to let the corresponding light beam enter, and, at the opposite, an output opening through which it emerges in the output waveguide, the output waveguide, as well as each input waveguide being laterally delimited by one or more metallic reflecting surfaces, and wherein at least a section of the output waveguide is divergent and widens in the direction of an output opening of the output waveguide.

A mode field adapter (MFA) is disclosed. The MFA is tapered and includes a passive core region and an active core region separated by a distance. Further, the passive core region includes first and second passive layers that are separated by another distance. The MFA is configured to receive an optical signal from a first waveguide, and alter, for transmission to a second waveguide, an optical mode of the optical signal. The optical mode is altered based on the distance between the first and second passive layers, the distance between the active and passive core regions, and the tapering of the MFA. The optical mode is altered such that an optical loss associated with the optical signal traversing from the first waveguide to the second waveguide by way of the MFA is within a tolerance limit.

A photonic integrated device includes a first waveguide and a second waveguide. The first and second waveguides are mutually coupled at a junction region the includes a bulge region.

An optimized SOI 2×2 multimode interference (MMI) coupler is designed by use of the particle swarm optimization (PSO) algorithm. Finite Difference Time Domain (FDTD) simulation shows that, within a footprint of 9.4×1.6 μm.sup.2, <0.1 dB power unbalance and <1 degree phase error are achieved across the entire C-band. The excess loss of the device is <0.2 dB.

Some embodiments of the present disclosure provide an optical sensor. The optical sensor includes a semiconductive substrate; a light sensing region on the semiconductive substrate; a waveguide region configured to guide light from a wave insert portion through a waveguide portion and to a sample holding portion; and an interconnect region below the waveguide region, and the interconnect region being disposed above the light sensing region. The waveguide portion includes a first dielectric layer comprising a first refractive index and at least one second dielectric layer comprising a second refractive index, wherein the second refractive index is smaller than the first refractive index.

In the examples provided herein, an apparatus has a mode converter coupled to a first waveguide to convert light propagating in a first set of spatial modes along the first waveguide to a second set of spatial modes. The apparatus also has a second waveguide coupled to the mode converter, where the second set of spatial modes propagate along the second waveguide in a first direction away from the mode converter. Further, the apparatus includes a coupler to couple a portion of the light propagating in the second set of spatial modes out of the second waveguide. Additionally, the second waveguide has an end facet away from the mode converter to reduce back reflection of the light not coupled out of the second waveguide to the first waveguide.

An optical mode converter includes a silicon substrate and a silicon dioxide film deposited on a top surface of the silicon substrate. A lithium niobate waveguide positioned on the silicon dioxide film having a slab and a rib that both taper in a direction of beam propagation through the optical mode converter. A doped silicon dioxide waveguide is positioned on top of the lithium niobate waveguide and has a slab that tapers in the direction of the optical beam propagation through the optical mode converter. The optical mode converter expands an optical mode of the optical beam propagating through the optical mode converter from a first optical mode size to a second optical mode size.