Arbitrary access to optical carriers in silicon photonic mode/wavelength hybrid division multiplexing circuits

Abstract

The manipulation of optical modes directly in a multimode waveguide without affecting the transmission of undesired signal carriers is of significance to realize a flexible and simple structured optical network-on-chip. In this Letter, an arbitrary optical mode and wavelength carrier access scheme is proposed based on a series of multimode microring resonators and one multimode bus waveguide with constant width. As a proof-of-concept, a three-mode (de)multiplexing device is designed, fabricated, and experimentally demonstrated. A new, to the best of our knowledge, phase-matching idea is employed to keep the bus waveguide width constant. The mode coupling regions and transmission regions of the microring resonators are designed carefully to selectively couple and transmit different optical modes. The extinction ratio of the microring resonators is larger than 21.0 dB. The mode and wavelength cross-talk for directly (de)multiplexing are less than −12.8 dB and −19.0 dB, respectively. It would be a good candidate for future large-scale multidimensional optical networks.

Reconfigurable optical add-drop multiplexers for hybrid mode-/wavelength-division-multiplexing systems

“…The wavelength tuning efficiency is measured to be ≈0.141 nm∕mW, and the whole FSR can be covered completely within the wavelength tuning range. Compared with the designs that can selectively access mode-/wavelength-carriers reported previously, 26,27 the present ROADM utilizing the modal field redistribution scheme possesses advantages of low insertion losses and low intermode cross talks, while no additional mode conversion devices are needed.…”

“…In 2021, an MDM switch was demonstrated so that any mode-/wavelength-channels can be directly accessed, but additional mode conversion devices were required to convert each mode into the highest-order mode supported by the MBW, which therefore increased the complexity 26 . In 2022, a three-mode (de)multiplexing device was demonstrated by introducing multimode MRRs, in which case the fundamental mode in the bus waveguide was evanescently coupled to the TE1 mode in the Euler-based MRR 27 . Nevertheless, it suffered from excess loss (EL) and cross talk, hindering its practical applications.…”

“…26 In 2022, a three-mode (de)multiplexing device was demonstrated by introducing multimode MRRs, in which case the fundamental mode in the bus waveguide was evanescently coupled to the TE 1 mode in the Eulerbased MRR. 27 Nevertheless, it suffered from excess loss (EL) and cross talk, hindering its practical applications. Recently, an MZI-based mode-sensitive phase shifter was proposed using subwavelength grating (SWG) structures to have varied temperature coefficients for different modes, which provided a new way for realizing the mode-selective phase manipulation with high extinction ratios.…”