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An ultracompact mode-order converting power splitter using a multimode interference (MMI) coupler with subwavelength gratings (SWGs) is proposed for mid-infrared (MIR) wavelength. Two symmetric oblique SWG-wires are embedded in the central input-region that is connected with the input waveguide. As a result, the input TE 0 mode is evenly coupled from the input waveguide into the MMI coupler due to the adiabatical mode evolution, and then two desired TE 1 modes are formed via self-imaging effect and further guided into the two output channels. Additionally, tapered structures and straight SWG wires are introduced into the two output channels to better obtain the required phase difference for the improvement of converting efficiency. Consequently, both TE 0 -to-TE 1 mode-order converting and power splitting, for the first time, are attained simultaneously in the present single device. Moreover, TE 0 -to-TE 2 power splitting can be readily achieved by flexibly changing the dimensions of the proposed device. Results show that a compact device length of 7 μ m with an insertion loss (IL) of 0.41 dB, a conversion efficiency (CE) of 99% and a crosstalk (CT) of -19.77 dB is obtained at the wavelength of 2 μ m; its bandwidth can be enlarged to 220 nm for IL < 0.79 dB and CE> 91%. Besides, fabrication tolerances are addressed and mode propagation profiles are illustrated. • Power splitting and mode-order conversion simultaneously in an individual component. • The total length of the proposed device power is only 7 microns. • The operating bandwidth can be enlarged to 220 nm. • The fabrication tolerances are large enough for fabrication. • The proposed device has the advantages of flexibility and expansibility. [ABSTRACT FROM AUTHOR]

A compact and polarization-independent three-guide power splitter using subwavelength gratings (SWGs) on the SOI platform is proposed and analyzed in detail, where the SWG structures are located at both sides of the central input waveguide and the inner sides of the two outside waveguides. The introduced SWG structures can effectively enhance the coupling strength for TE mode, while that for TM mode is hardly affected. Consequently, by carefully choosing the structural parameters, the input TE mode can be evenly coupled from the central input waveguide to the outside waveguides, with the same coupling length for TM mode, thus a polarization-independent power splitter is realized. Results show that a compact power splitter of 8.5 μ m in coupling length is achieved with an insertion loss (IL) of 0.1 dB (0.085 dB) and reflection loss (RL) of −39 dB (−46 dB) for TE (TM) mode at the wavelength of 1. 55 μ m , and the operation bandwidth is up to 170 nm (from 1.48 to 1. 65 μ m) when IL <0.8 dB, RL <−20 dB and splitting ratio (SR) ∼ 1.001 for both polarizations. In addition, fabrication tolerances to the key structural parameters are presented and field evolution through the device is illustrated [ABSTRACT FROM AUTHOR]