Abstract
In this paper, we report a two-layer five-port diffraction grating by a polarization-independent design under normal incidence. To be different from conventional five-port gratings, initially, we design a novel two-layer grating with operation in transmission. Next, we firstly design a polarization-independent grating with five-port splitting output. On the one hand, the accurate grating vector parameters are optimized using rigorous coupled-wave analysis (RCWA) approach. On the other hand, the inherent coupling mechanism happened in the grating region can be well explained by employing simplified modal method (SMM). More importantly, all reported conventional five-port beam splitter gratings were designed based on polarization dependent. Although they could obtain high diffraction efficiency for TE or TM polarization, it requires more complicated and time-consuming fabrication processes in practical grating applications. Thus, this work can open up a possible thought for designing polarization-independent multi-port beam splitter diffraction gratings.
Highlights
Polarization-Independent diffraction gratings are key optical diffraction elements, which can be found in potential optical applications in semiconductor optical amplifiers [1], polarizationindependent filter [2], three-dimensional photonic integration [3], on-chip optoelectronic integration [4], two spectral beam combined fiber amplifiers [5] and so on
In this paper, we report a two-layer five-port diffraction grating by a polarizationindependent design under normal incidence
To be different from conventional five-port gratings, initially, we design a novel two-layer grating with operation in transmission
Summary
Polarization-Independent diffraction gratings are key optical diffraction elements, which can be found in potential optical applications in semiconductor optical amplifiers [1], polarizationindependent filter [2], three-dimensional photonic integration [3], on-chip optoelectronic integration [4], two spectral beam combined fiber amplifiers [5] and so on. In most reported traditional works, design of numerous polarization-independent beam splitter gratings are excessively relied on numbers of different output diffraction orders. Under second Bragg incidence, It is relatively easy to obtain optimized polarization-independent high-efficiency grating [20] or two-port beam splitter grating [21]. Under normal incident condition, some of five-port reflective or transmission beam splitter gratings [28], [29] are numerically optimized based on polarization-dependent designs, which are limited for applying in optical domains. We firstly propose and numerically optimize a polarization-independent two-layer transmission five-port diffraction grating under normal incidence. Compared with reported reflective or transmission five-port beam splitter gratings, our proposed novel two-layer five-port grating element has merits of polarization-independent property and fine splitting performance for TE and TM polarizations simultaneously. Our designed five-port grating element can be found potential applications in optical measurement technology and three-dimensional holography
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