Broadband and CMOS compatible polarization splitter-rotator based on a bi-level taper

Metasurface-assisted amorphous germanium-tin waveguide bolometer for mid-infrared photodetection

An amorphous germanium-tin (a-Ge0.83Sn0.17) waveguide bolometer featuring a one-dimension (1D) metasurface absorber is proposed for mid-infrared photodetection at room-temperature. The device is based on the germanium-on-silicon (GOS) photonic platform. The impacts of the 1D metasurface on the performances of the waveguide bolometer are investigated. The responsivity of the a-Ge0.83Sn0.17 waveguide bolometer could be significantly enhanced by the metasurface. A responsivity of around -3.17%/µW within the 4.1 ∼ 4.3 µm wavelength range is achieved. In addition, a 3-dB roll-off frequency higher than 10 kHz is obtained.

Broadband and CMOS-compatible polarization splitter and rotator built on a silicon nitride-on-silicon multilayer platform

A broadband and CMOS-compatible polarization beam splitter and rotator (PSR) built on the silicon nitride-on-silicon multilayer platform is presented. The PSR is realized by cascading a polarization beam splitter and a polarization rotator, which are both subtly constructed with an asymmetrical directional coupler waveguide structure. The advantage of this device is that the function of PSR can be directly realized in the SiN layer, providing a promising solution to the polarization diversity schemes in SiN photonic circuits. The chip is expected to have high power handling capability as the light is input from the SiN waveguide. The use of silicon dioxide as the upper cladding of the device ensures its compatibility with the metal back-end-of-line process. By optimizing the structure parameters, a polarization conversion loss lower than 1 dB and cross talk larger than 27.6 dB can be obtained for TM-TE mode conversion over a wavelength range of 1450 to 1600 nm. For TE mode, the insertion loss is lower than 0.26 dB and cross talk is larger than 25.3 dB over the same wavelength range. The proposed device has good potential in diversifying the functionalities of the multilayer photonic chip with high integration density.

Broadband ultra-compact polarization splitter-rotator using diagonally overlapped bi-layer architecture

A broadband and ultra-compact polarization splitter-rotator based on diagonally overlapped bi-layer architecture and an asymmetrical directional coupler is proposed on a silicon-on-insulator platform. By leveraging the structure over supermode theory, a 1-dB bandwidth of 220 nm, extinction ratio (ER) of <19dB, and cross talk (XT) of <-15.85dB within the span of 1400-1700 nm and coupling length of 4.62 µm are achieved. In addition, TM₀-TE₀ conversion loss of ∼0.19dB, ER of 35.88 dB, and XT of -30.46dB can be obtained at 1550 nm. The fabrication tolerances are also analyzed, indicating that the insertion losses remain below 1 dB over 1460-1620 nm in terms of width errors and layer-to-layer misalignments within ±10nm. The results show that the proposed device is very suitable to utilize between fibers and for polarization diversity of on-chip systems for broadband operation as well as ultra-compact integration.

Shortcut to adiabaticity in a silicon polarization splitter rotator using multi-wavelength adiabaticity engineering

We introduce adiabaticity engineering in coupled waveguide devices to achieve shortcuts to adiabaticity in multi-wavelength systems. By engineering the adiabaticity distribution using a single control parameter, we obtain large operating bandwidth in a compact device. Multi-wavelength adiabaticity engineering is applied to the design of silicon polarization splitter-rotators. The total length of the designed polarization splitter-rotator is 141 μm, and simulations show that the device exhibits extinction ratios above 28 dB and 16 dB for the TE₀ and TM₀ modes, respectively, with a bandwidth of 300 nm (from 1.4 μm to 1.7 μm). The fabrication tolerance of the designed device is also simulated.