A Two-Channel Silicon Nitride Multimode Interference Coupler with Low Back Reflection

Abstract

Optical communication systems based on silicon (Si) multimode interference (MMI) wavelength-division multiplexing (WDM) technology can suffer from back reflection. This undesirable characteristic causes losses and is a key problem that can lead to performance limitations. To overcome this limitation, we proposed a new study on how to divide two wavelengths by understanding the light coupling mechanism of the silicon nitride (SiN) MMI coupler over the C-band window and showed four different options to design a two-channel demultiplexer. The best option for a two-channel SiN MMI coupler with low back reflection losses operating in the C-band spectrum was selected. Based on simulation results, the proposed device can transmit two channels with a spacing of 20 nm between wavelengths in the C-band. Moreover, the device has a low power loss range of 0.895–0.936 dB, large bandwidth of 16.96–18.77 nm, and good crosstalk of 23.5–25.86 dB. Usually, a unique design such as angled MMI is required when using Si MMI technology to reduce the back reflection losses. Due to the use of SiN, which has a low refractive index, we obtained a 40.4 dB back-reflection loss without using this angled MMI design. Therefore, this MMI demultiplexer based on SiN can be used in optical communication systems based on the WDM technique to obtain a high data transfer rate in conjunction with low back-reflection losses.

Data Center Four-Channel Multimode Interference Multiplexer Using Silicon Nitride Technology

“…Back reflections arise from mismatches within the waveguide, leading to a portion of the light being reflected back towards the source [ 36 ]. Si 3 N 4 offers an intrinsic advantage in this regard [ 37 ], demonstrating inherently low back reflection [ 38 , 39 ], which is further optimized through the careful design of waveguide tapers [ 40 ]. This characteristic is crucial in maintaining the integrity of the signal and ensuring the reliable operation of photonic devices, particularly in systems where wavelength stability and signal clarity are paramount.…”

Magnetically controllable multimode interference in topological photonic crystals

“…Conventionally, multimode interference is realized by modifying the size of waveguides [34][35][36][37][38] , including their width or length, or controlling the refractive indices of the system with electrooptic effect 39,40 . However, back reflection loss 41 is a key problem that leads to performance limitations of traditional multimode interference devices. Based on the backscattering-immune property of topologically protected CEMs, topological multimode waveguide can overcome this limitation with one-way propagation, and support higher mode density and coupling efficiency 18 , thereby offer opportunities for design of novel topological devices for power manipulation.…”

Post-Processing Trimming of Silicon Photonic Devices Using Femtosecond Laser

“…Recently, silicon photonic integrations, based on complementary metal oxide semiconductor (CMOS)-compatible processes, have shown great application prospects in optical communications, optical interconnections, optical sensing, and optical computing because of their compact size, low power consumption, and low cost [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. The process nodes used by mainstream silicon photonic manufacturers are usually 130 nm or 180 nm for low-cost production, which inevitably introduces fabrication errors in the devices.…”