Abstract
We propose a 1310/1550 nm wavelength diplexer on a 220-nm silicon-on-insulator (SOI) platform. The device is based on a compact two-mode interference (TMI) coupler enabled by a subwavelength grating (SWG) slot. The ideal beat length ratio of 2:1 is achieved with the transverse magnetic (TM) mode by fine-tuning the SWG slot parameters, resulting in a TMI length of only 37 µm. We reveal that the key to high extinction ratio (ER) is the careful design of the tapers, and the device achieves high ERs of 28.05/42.54 dB at 1310/1550 nm with simulation. The measured bandwidths for ER <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$>$</tex-math></inline-formula> 15 dB are 82 nm and 56 nm at O- and C-band. Moreover, the design guarantees large calculated 1-dB-insertion-loss (IL) bandwidths of 192/123 nm at 1310/1550 nm. To the best of our knowledge, this is the first experimental demonstration of a high-performance compact silicon 1310/1550 nm diplexer based on a TMI coupler.
Highlights
P HOTONIC integrated circuits (PICs) implemented on the silicon-on-insulator (SOI) platform have attracted a lot of attention in recent years, because they enable dense integration of photonic devices while remaining compatible with complementary metal-oxide-semiconductor (CMOS) processes
We propose in this letter the first experimental demonstration of a compact 1310/1550 nm wavelength diplexer based on a two-mode interference (TMI) coupler
The TMI coupler [22] is a special type of multimode interference (MMI) coupler in which only two modes are supported in the mode interference section
Summary
P HOTONIC integrated circuits (PICs) implemented on the silicon-on-insulator (SOI) platform have attracted a lot of attention in recent years, because they enable dense integration of photonic devices while remaining compatible with complementary metal-oxide-semiconductor (CMOS) processes. A more recent work [21] applied the similar idea to add double SWG slots to the MMI coupler, further reducing the device length. Both designs were only verified by simulation, and the extinction ratios (ERs) are relatively low. The TMI coupler [22] is a special type of MMI coupler in which only two modes are supported in the mode interference section It has a relatively short coupling length, and it has been studied on the SOI platform [23]. We show that by inserting an SWG slot in an MMI coupler and a careful design of the tapers, we can realize two-mode interference in the device and reduce the coupling length. As for the IL, the calculated 1-dB-IL bandwidths are 192/123 nm at O/C-bands, which satisfies the International Telecommunication Union (ITU) standard
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