<p>To obtain efficient and stable light trapping, angle rotation is introduced to form rotated square pillar array grating (SPAG) solar cells. Compared with the unpatterned stack slab and the optimized uniform SPAG cells, the maximum short-circuit current (<italic>J</italic><sub>sc</sub>) of the optimized rotated SPAG is increased by 78.54% and 3.21%, respectively. Moreover, besides the fact that the low-incidence angular sensitivity of <italic>J</italic><sub>sc</sub> could be maintained, <italic>J</italic><sub>sc</sub> of the optimized rotated SPAG will always be larger than that of the optimized uniform SPAG at any incident angle. Furthermore, when the structural parameters of the subsquare pillar slightly deviate from the optimum, the absorption only deceases slightly as well, which indicates both a high structural tolerance and a stable absorption performance. In addition, our results show not only that the proposed rotated SPAG is promising to make light trapping efficient and stable but also that introducing rotation disorders is promising for other high-absorption pseudounordered surface structures.</p>
In this paper, we propose the simplest one-dimensional grating waveguide to obtain the wideband slow light. An ideal band indicating group index of 18.3 and bandwidth of 10.3 nm is obtained by plane wave expansion method, which is also verified in the finite-difference time-domain numerical simulation when a Gaussian pulse with bandwidth of 10.3
nm is input into the grating waveguide. Thus, this simple one-dimensional grating waveguide is believed to be widely
used as wideband and low loss slow light delay for optical buffering and signal processing.
In recent years, silicon nanophotonic devices have attracted more and more attention due to their compactness, low power consumption, and easy integration with other functions. In addition to the higher index of silicon material providing stronger light confinement, the optical resonance associated with the novel structure design also enhances the performance of nanophotonic devices and offers stronger light-matter interaction. Silicon nanophotonic devices such as polarization beamsplitters, mirrors and reflectors, slow light waveguides, and microring sensors are studied, and all of them demonstrate much better performances due to the incorporated optical resonance enhancement.