Grating Input/Output Coupler

SiN/SiO/Air waveguide-grating structure @ 1.5 µm:

• Input coupler: rectangular 1st order surface-relief grating with 50 periods, p = 0.85 µm
• Output coupler: 1st order, 40 periods, p = 1.05 µm
• Model domain: ~ 100 by 10 wavelengths, 105 shape functions, ~40k unknowns

TM-polarization, angle of incidence = -7.5° (off-resonant)

TM-polarization, angle of incidence = -10° (resonant)

A comparison of different models (input coupler only)

brought the following results:

• VMM (with equivalent current excitation)

  • Exection time ~ 4 seconds / angle-point
• Commercial FDTD package (with field excitation)

  • Execution time ~ 1 hour / angle-point
• Floquet-Bloch analysis based on N. Finger et al., IEEE Journal of Quantum Electronics 35, 832 (1999)