We design a novel slow-light silicon photonic crystal waveguide which can operate over an extremely wide flat band for ultrafast integrated nonlinear photonics. By conveniently adjusting the radii and positions of the second air-holes rows, a flat slow-light low-dispersion band of 50 nm is achieved numerically. Such a slow-light photonic crystal waveguide with large flat low-dispersion wideband will pave the way for governing the femtosecond pulses in integrated nonlinear photonic platforms based on CMOS technology.
We propose and experimentally demonstrate an on-chip switchable polarization beam splitter (PBS) using silicon waveguides. To the best of our knowledge, it is the first demonstration of an on-chip PBS that is not only able to split polarization beams but can be tuned to allow these beams to switch the output paths. The design of the switchable PBS is based on a directional coupler. Measurements show extinction ratios of >12 dB in both the initial state and the switched state, which is realized by heating the device up to 57°C. By adding switching ability to an on-chip PBS, this work is expected to benefit quantum technology, communications, microwave photonics, etc.
Microring resonators (MRRs) with ultracompact footprints are preferred for enhancing the light-matter interactions to benefit various applications. Here, ultracompact titanium dioxide (TiO 2 ) MRRs with sub-10-μm radii are experimentally demonstrated. Thanks to the large refractive index of TiO 2 , the quality factors up to ∼7.9 × 10 4 and ∼4.4 × 10 4 are achieved for TiO 2 MRRs with radii of 10 μm and 6 μm, respectively, which result in large nonlinear power enhancement factors (>113) and large Purcell factors (>56). The four-wave mixing (FWM) measurements indicate that, compared to the large MRR, the FWM conversion efficiency of the ultracompact TiO 2 MRRs can be greatly improved (e.g., −25 dB versus −31 dB), a harbinger of significant superiorities. Demonstrations in this work provide more arguments for the TiO 2 waveguides as a promising platform for various on-chip photonic devices.
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