Ultracompact, Scalable and Flexible Multi-Order Mode Converter for TE0/TE1 Dual-Mode Input

Different from conventional converters only converting one given mode to a single desired one, we here propose a multi-order conversion scheme for TE0/TE1 dual-mode input by exploiting asymmetric multimode interference (AMMI) and beam shaping, where an inverse-tapered subwavelength gratings array (ITSWGA) is sandwiched between two AMMI waveguides, followed by asymmetric tapers, respectively. For input TE0/TE1 mode, it is divided into two modal components by the ITSWGA and then excites p-th and q-th (p not equal q, p = 1, 2 & q = 2, 3) modes in two AMMI waveguides via self-imaging effect, where followed tapers can further amend the phase differences of modal components for target modes via beam shaping. Thus, p-th and q-th modes can be obtained in dual-output channels simultaneously, for both input TE0 and TE1 modes. Results show that the bandwidth can be enlarged to 90 nm (the worst-case: p = 2 & q = 3) for crosstalk < -10 dB and conversion efficiency >80%, in an ultracompact length of only 8.7 mu m, for the dual-mode input. Significantly, the dual-output channels can be flexibly combined into a single-output channel by tapers to form an MZI-like structure, which can convert TE0 to TE0+i mode and TE1 to TE1+i mode (i = 2, 4 and 6) simultaneously, realizing dual-order conversions in a single structure, and results of the best-case (i = 2) are conversion efficiency = 97.1% (98%), insertion loss = 0.32 dB (0.53 dB), and crosstalk = -16.89 dB (-19.72 dB) @ 1.55 mu m for TE0-to-TE2 (TE1-to-TE3) conversion, within a length of 12.23 mu m.

Automated summary

This paper proposes a multi-order conversion scheme using asymmetric multimode interference and beam shaping, capable of converting TE0 and TE1 modes to their respective p-th and q-th modes. The dual-output channels can also be combined into a single-output channel by changing the structure.