A thermally bi-directionally tunable arrayed waveguide grating (TBDTAWG) is proposed and demonstrated on a silicon-on-insulator (SOI) platform. The device is composed of passive and active designs for realizations of an AWG and fine tuning of its filtering responses. Given that the required length difference between adjacent arrayed waveguides for the SOI platform is considerably short (∼3–5 µm) due to a high index contrast, an S-shaped architecture with a larger footprint instead of a rectangular one is employed in the AWG. Bi-directionally tunable functions, i.e., both red- and blue-shift tunable functions, can be achieved by using two triangular thermal-tuning regions with complementary phase distributions in the S-shaped architecture despite using only materials with positive thermo-optic coefficients, i.e., Si and SiO2. Measurement results illustrate that both red- or blue-shifted spectra can be achieved and a linear bi-directional shift-to-power ratio of ±30.5 nm/W as well as a wide tuning range of 8 nm can be obtained under an electrical voltage range of 0–2.5 V, showing an agreement between the measurement results and two-dimensional simulation results. This also shows the potential of the proposed TBDTAWG for automatically stabilizing the spectral responses of AWG-based (de)multiplexers for coarse or dense wavelength division multiplexing communication systems by using a feedback control circuit.
We design a waveguide crossing with composite subwavelength (SW) structures, i.e., bridged SW grating (BSWG) waveguide structures and diagonally periodic holes (DPHs), on a partial parabolic single layer crossing (PPSLC) to improve its transmission. The BSWG is located before/after the input/output regions of the PPSLC and the DPHs are in the crossing region of the PPSLC. This waveguide crossing occupies a footprint of 6.2 μm × 6.2 μm upon a silicon-on-insulator wafer with 220-nm silicon device layer on 2-μm buried oxide. We successfully gain simulated results of the transmission up to 98.72% (−0.056 dB) and the crosstalk as low as −65 dB at an input wavelength of 1.55 μm.
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
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