Design and Fabrication of 1x2 Multimode Interference Coupler Using Photosensitive Permanent Material for Wavelength Division Demultiplexing

Abstract

This report presents a 1x2 multimode interference coupler using photosensitive permanent material for wavelength division demultiplexing (WDM). The multimode interference (MMI) for multiplexer (MUX) and/or demultiplexer (DEMUX) architectures used different coupling lengths at long beat lengths for individual signal propagation. The MMI design was proposed with a short beat length and a single coupling length of two signals. The proposed MMI of a 1x2 coupler was simulated with the beam propagation method (BPM) using silicon dioxide (Si) and photosensitive permanent material “TMMR-S2000” as the cladding and core with the refractive indices of 1.45 and 1.57, respectively. The two light signals with 1310 nm and 1550 nm wavelengths were propagated through the 2.8 m wide input waveguide section, with the coupling length and width of 510 μm and 6.7 μm, respectively. The MMI was later fabricated using conventional photolithography with the help of hard baking. The simulation results showed that a high percentage of the two signals’ splitting power was realized. The performance characterization of the system was determined in terms of the insertion loss and extinction ratio. According to the numerical simulations, the extinction ratios for 1310 nm and 1550 nm lights are 19 dB and 17 dB, respectively, and the insertion losses for these wavelengths are 0.97 dB and 0.46 dB, respectively. When comparing the simulation results of the intensity distribution with the near-field patterns of the fabricated MMI at a coupling wavelength of 1310 nm, the desired splitting results were achieved. However, at 1550 nm, the findings were unfavourable.