Dual-mode waveguide crossing utilizing taper-assisted multimode-interference couplers

Abstract

A dual-mode waveguide crossing is proposed and realized for the application of on-chip multimode interconnection. The present structure is realized by two 90° crossed multimode-interference (MMI) couplers. By properly choosing the width and length of the MMI section, the self-images for both the incident TM₀ mode and the TM₁ mode could be at the center of the crossing. The characterization results for the fabricated device show that low insertion loss below ∼1.5 dB and low crosstalk below ∼-18 dB can be achieved over a large bandwidth more than 80 nm for both the TM₀ and TM₁ modes.

Metamaterial‐Based Maxwell's Fisheye Lens for Multimode Waveguide Crossing

“…However, the beat lengths are different for higher‐order modes, so that the MMI‐based crossing cannot be directly exploited in the multimode realm. To realize the multimode waveguide crossing, one can optimize the parameters to ensure that the total length of MMI is the common multiple of beat lengths for the fundamental and higher‐order modes, so that the self‐images of all the incident modes are at the crossing center . However, the footprint of such optimized MMI can be quite large and the losses are significant.…”

“…To realize the multimode waveguide crossing, one can optimize the parameters to ensure that the total length of MMI is the common multiple of beat lengths for the fundamental and higher-order modes, so that the self-images of all the incident modes are at the crossing center. [23] However, the footprint of such optimized MMI can be quite large and the losses are significant. An alternative scheme to achieve the low-loss crossings is to utilize the ridge waveguide expanders, which can maintain the mode confinement over the crossing section and efficiently reduce the losses by reducing the lateral index contrast.…”

Silicon-based multimode waveguide crossings

“…Multimode waveguide crossings are the essential components in high-density and large-scale on-chip MDM optical network. Over the past decades, many schemes have been proposed and experimentally demonstrated including conventional MMI coupler [33][34][35], Maxwell's fisheye lens [36][37][38] and inverse-designed MMI coupler [39]. The demonstrated devices with the high performance of compact footprint, low insertion loss and low crosstalk will show great potential in practical applications for high-density and large-scale MDM systems.…”

“…Recently, several schemes of multimode waveguide crossings based on MMI couplers were introduced and experimentally demonstrated by some special designed structures. A dual-mode waveguide crossing was proposed and demonstrated [33], as shown in figure 1(a). The proposed device is composed of two 90 • crossed MMI couplers and four tapers at each input/output port.…”

“…After a brief introduction, we demonstrate and present a variety of multimode waveguide crossing schemes such as On-chip multimode waveguide crossings based MMI coupler. (a) A dual-mode waveguide crossing based on MMI coupler [33]. (b) A two-mode waveguide crossing based on symmetric Y-junction [34].…”