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gplugins.modes.find_modes_coupler

gplugins.modes.find_modes_coupler#

gplugins.modes.find_modes_coupler(tol: float = 1e-06, wavelength: float = 1.55, mode_number: int = 1, parity=0, cache_path: str | Path | None = PosixPath('/home/runner/.gdsfactory/modes'), overwrite: bool = False, *, single_waveguide: bool = False, **kwargs) → dict[int, Mode]#

Computes mode effective and group index for a rectangular waveguide.

Parameters:

  • tol – tolerance when finding modes.

  • wavelength – wavelength in um.

  • mode_number – mode order of the first mode.

  • parity – mp.ODD_Y mp.EVEN_X for TE, mp.EVEN_Y for TM.

  • cache_path – path to cache folder. None to disable caching.

  • overwrite – forces simulating again.

  • single_waveguide – if True, compute a single waveguide. False computes a coupler.

Keyword Arguments:

  • core_width – core_width (um) for the symmetric case.

  • gap – for the case of only two waveguides.

  • core_widths – list or tuple of waveguide widths.

  • gaps – list or tuple of waveguide gaps.

  • core_thickness – wg height (um).

  • slab_thickness – thickness for the waveguide slab.

  • core_material – core material refractive index.

  • clad_material – clad material refractive index.

  • nslab – Optional slab material refractive index. Defaults to core_material.

  • ymargin – margin in y.

  • sz – simulation region thickness (um).

  • resolution – resolution (pixels/um).

  • nmodes – number of modes.

  • sidewall_angles – waveguide sidewall angle (radians), tapers from core_width at top of slab, upwards, to top of waveguide.

Returns: Dict[mode_number, Mode]

compute mode_number lowest frequencies as a function of k. Also display “parities”, i.e. whether the mode is symmetric or anti_symmetric through the y=0 and z=0 planes. mode_solver.run(mpb.display_yparities, mpb.display_zparities)

Above, we outputted the dispersion relation: frequency (omega) as a function of wavevector kx (beta). Alternatively, you can compute beta for a given omega – for example, you might want to find the modes and wavevectors at a fixed wavelength of 1.55 microns. You can do that using the find_k function:

single_waveguide=True

  __________________________
  |
  |
  |         width
  |     <---------->
  |      ___________   _ _ _
  |     |           |       |
sz|_____|           |_______|
  |     core_material       | core_thickness
  |slab_thickness    nslab  |
  |_________________________|
  |
  |        clad_material
  |__________________________
  <------------------------>
                sy

single_waveguide=False

  _____________________________________________________
  |
  |
  |         widths[0]                 widths[1]
  |     <---------->     gaps[0]    <---------->
  |      ___________ <-------------> ___________      _
  |     |           |               |           |     |
sz|_____|           |_______________|           |_____|
  |    core_material                                  | core_thickness
  |slab_thickness        nslab                        |
  |___________________________________________________|
  |
  |<--->                                         <--->
  |ymargin               clad_material                   ymargin
  |____________________________________________________
  <--------------------------------------------------->
                           sy
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