Slow light miniature devices with ultra-flattened dispersion in silicon-on-insulator photonic crystal (original) (raw)
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Wideband ultraflat slow light with large group index in a W1 photonic crystal waveguide
We demonstrate that slow light with large group-index, wide band and low dispersion can be realized in a silicon-on-insulator W1-type photonic crystal waveguide by simply shifting the first two rows of air-holes adjacent to the waveguide to specific directions. Keeping the group index at 46, 60, 86, 111, 151 and 233, respectively, while restricting its variation within a 10 % range, we accordingly obtain a slow light bandwidth of 9.0 nm, 6.7 nm, 4.6 nm, 3.3 nm, 2.4 nm and 1.7 nm, respectively. The normalized delay-bandwidth product keeps around 0.25 for all cases. Moreover, we obtain ultraflat slow light with bandwidths over 3.0 nm, 2.4 nm, 1.6 nm, 1.3 nm, 0.93 nm and 0.6 nm, respectively, where the group index variation is in a range of only 0.8 %. Numerical simulations are performed utilizing the 2D plane wave expansion method and the finite-difference time-domain method.
Experimental GVD engineering in slow light slot photonic crystal waveguides
Scientific reports, 2016
The use in silicon photonics of the new optical materials developed in soft matter science (e.g. polymers, liquids) is delicate because their low refractive index weakens the confinement of light and prevents an efficient control of the dispersion properties through the geometry. We experimentally demonstrate that such materials can be incorporated in 700 μm long slot photonic crystal waveguides, and hence can benefit from both slow-light field enhancement effect and slot-induced ultra-small effective areas. Additionally, we show that their dispersion can be engineered from anomalous to normal regions, along with the presence of multiple zero group velocity dispersion (ZGVD) points exhibiting Normalized Delay Bandwidth Product as high as 0.156. The reported results provide experimental evidence for an accurate control of the dispersion properties of fillable periodical slotted structures in silicon photonics, which is of direct interest for on-chip all-optical data treatment using n...
Slow light enhancement of nonlinear effects in silicon engineered photonic crystal waveguides
We report nonlinear measurements on 80µm silicon photonic crystal waveguides that are designed to support dispersionless slow light with group velocities between c/20 and c/50. By launching picosecond pulses into the waveguides and comparing their output spectral signatures, we show how self phase modulation induced spectral broadening is enhanced due to slow light. Comparison of the measurements and numerical simulations of the pulse propagation elucidates the contribution of the various effects that determine the output pulse shape and the waveguide transfer function. In particular, both experimental and simulated results highlight the significant role of two photon absorption and free carriers in the silicon waveguides and their reinforcement in the slow light regime.
2008
Photonic crystal waveguides (PCW) on silicon-on-insulator (SOI) are considered as a promising guiding platform with flexible guiding properties for dense photonics integration. Although SOI is a versatile material for photonics integration, PCWs fabricated on SOI substrates suffer from small guiding bandwidth due to the coupling to leaky TM-like modes. The purpose of this work is to present a systematic approach to increase the low-loss guiding bandwidth of PCWs on SOI. This has been achieved by reducing the interaction of low-group-velocity modes with the surrounding photonic crystal. By this method the low-loss bandwidth of a W1 PCW is increased from 2.5 nm to 12 nm which is the highest reported for this type of waveguide. We also present a detailed analysis of transmission properties of W1 PCWs and elaborate on the coupling to TM-like guided modes present in the low-loss transmission bandwidth of this device.