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1

Complex trapezoid grating for light trapping in thin-film solar cells: super-fine structure

Fang Junfei, Gou Yuchun, Deng Jianping

Optica Applicata

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2020

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Vol. 50, nr 3

391--400

EN

The research of the optimal surface structure has attracted considerable interest because of its potential application in light trapping in thin-film solar cells (TFSCs). In this paper, a super-fine structure named complex trapezoid grating is proposed to improve the optical absorption comparing to the conventional simple trapezoid grating in a-Si:H TFSCs. The numerical calculation by utilizing rigorous coupled-wave analysis (RCWA) is conducted to obtain the optical absorption of the structured surface. The results demonstrate that, compared to a planar slab, the optimized-simple trapezoid grating shows 97% enhancement of power conversion efficiency η while the complex trapezoid grating shows 131% enhancement. Obviously, the complex trapezoid grating exhibits a better performance than the simple grating, which is due to the perfect antireflective effect and microcavity resonance effect. The angular response of the optical absorption in a-Si:H TFSCs was also investigated. The results further indicate that it is a better way to select the complex trapezoid grating in improving the optical absorption of silicon-based TFSCs.

2

Highly-efficient three-port output by metal-mirror-based grating

Li H., Wang B., Shu W., Chen L., Lei L., Zhou J.

Optica Applicata

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2016

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Vol. 46, nr 1

87--92

EN

A highly-efficient three-port output of metal-mirror-based grating is proposed in this paper. The metal-mirror-based grating can function as a beam splitter which can diffract the normal incident wave into the 0th and the +/- 1st orders for both TE and TM polarizations with the usual duty cycle of 0.5. The analysis of the grating parameters can be optimized by rigorous coupled-wave analysis. The high efficiency for TE and TM polarizations shall be realized. By means of the numerical simulation, the depth and connecting layer thickness of grating can be accurately calculated. The efficiency of per port is near 33.3%, so the novel three-port output grating with a connecting layer would be an excellent optical element.

3

Polarization-independent metal-dielectric grating with improved bandwidth

Wang B, Li H, Shu W, Li W, Li C, Lei L, Zhou J

Optica Applicata

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2015

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Vol. 45, nr 1

71--77

EN

A polarization-independent reflective grating with improved bandwidth is presented based on the mixed metal-dielectric grating. The novel grating is composed of the substrate, the metal slab, two dielectric layers, and the covering layer. The grating parameters are optimized for the special duty cycle of 0.6 at an incident wavelength of 1550 nm used in dense wavelength division multiplexing (DWDM). With the designed grating, high efficiency can be diffracted into the reflective –1st order for both TE and TM polarizations, where the polarization-independence is exhibited. Most importantly, the efficiency of more than 90% can be achieved within the incident wavelength bandwidth of 1262–1686 nm, where the bandwidth is improved greatly compared with the reported surface-relief single-layer grating. The reflective grating can have advantages of high efficiency, polarization-independence, and wide bandwidth, which should be useful for DWDM applications.

4

Reflective diffraction with high efficiency and beam splitter by metal-mirror-based grating

Wang B., Lei L., Chen L., Zhou J.

Optica Applicata

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2012

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Vol. 42, nr 3

473-479

EN

It is interesting and desirable to achieve two functions of high efficiency and two-port output with one reflective grating, which is not easy to acquire by multilayer coatings. We describe the reflective high efficiency element and the two-port beam splitter by the metal-mirror-based grating. By modal method, the design guideline is proposed according to the two-beam interference of the excited modes by incident TE and TM polarizations. Using rigorous coupled-wave analysis (RCWA), accurate grating parameters are optimized by numerical calculation. This indicates that wideband property can be achieved for such a reflective dual-function grating. Furthermore, the element can also be used for beam splitting for TE polarization with the pre-determined angle of incidence. With merits of wideband and so many functions, the reflective elements presented should be useful in a variety of optical systems.

5

Numerical optimization of polarizing beam splitter gratings and modal explanation

Wang B.

Optica Applicata

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2010

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Vol. 40, nr 1

101--107

EN

We describe high-density deep-etched fused-silica transmission polarizing beam splitter (PBS) gratings and their simple physical explanation. Optimized numerical results of the grating depth and period are given using the rigorous coupled-wave analysis in order to achieve high extinction ratio and efficiency for the usual laser wavelengths 351, 441.6, 532, 632.8, 800, and 1053 nm. The physical mechanism of such a PBS grating can be well explained with the effective indices of the modes for TE/TM polarization, which is a useful extension of the modal method for different structures reported in this paper. Compared with the work of Clausnitzer et al., fused-silica gratings can work as PBSs for not only the special duty cycle of 0.51 but also the usual duty cycle of 0.50. These numerical results and simple physical explanation provide a useful guideline for the design of a PBS grating.