solve(solver=’radial’)

pyMMF.propagationModeSolver.solve(self, solver: str = 'default', curvature: bool = None, storeData: bool = True, options: dict = {})

Solves the scalar wave equation for an axisymmetric index profile define by a radial function. The IndexProfile object provided must be initialized with the initFromRadialFunction method.

See also

For documentation for the rest of the parameters, see pyMMF.propagationModeSolver.solve()

Options:

degenerate_modestring (‘exp’, or ‘sin’), optional

Choice for degenerate subspaces.

• ‘exp’ return the orbital angular momentum modes, for an azimuthal index m>0, the azimuthal function is exp(i*-m*theta) and exp(i*m*theta)

• ‘sin’ return the linear polarized modes, they have real values of the field with an azimuthal function of sin(m*theta) and cos(m*theta) for m>0.

Default is ‘exp’.

min_radius_bcfloat, optional

Minimum radius for the boundary condition in units of the radius of the fiber set in the index profile. The algorithm will try to find a solution of the field mode profile that vanishes at this radius. If not successfull, it will multiply this maximum radius by change_bc_radius_step and try again. Default is 4.

change_bc_radius_stepfloat, optional

Factor to change the boundary condition radius when not successfull reaching the vanishing boundary condition equalt to zero at min_radius_bc. Set the next radius to r_max = r_max * change_bc_radius_step. Default is 0.9.

N_beta_coarseint, optional

Number of beta values in the initial rought scan for each radial number l. Before trying to find the beta value that satisfies the boundary condition, we scan the range of betas admissible for propagating modes to find the changes of the sign of the farthest radial point. It gives the number of modes and initial guesses for the beta values. Default is 1_000.

r_maxfloat or None, optional

Maximum radius for the search. Default is None, it fixes the value to np.max(indexProfile.R) i.e. the maximum radius of the index profile map.

dhfloat or None, optional

Spatial resolution. Note that the algorithm find the solution of a 1D problem, resolution can be increased to improve the accuracy of the solution with much less computational cost than the 2D problem. Default is None, it fixes the value to indexProfile.areaSize / indexProfile.npoints.

beta_tolfloat or None, optional

Tolerance for the beta value. Default is is None, it fixes the value to np.finfo(np.float64).eps.

field_limit_tolfloat, optional

Tolerance for the field limit. If the field at r_max is below this value, the field is considered to be zero, and the boundary condition is considered to be met. Default is 1e-3.

beta_minfloat or None, optional

Minimum beta value considered in the search. Changing this value can return non-propagating modes. Default is None, it set the values to 2*np.pi/wl * n_func(r_max0). Note that for a index profile that does not monotonically decrease with the radius, this value can lead to the algorithm to miss some propagating modes.

save_funcbool, optional

Save the radial and azimuthal functions. If try, it stores the results in the data attribute of the Modes object. Fields are: - “radial_func”: the extrapolated radial function, - “r_max”: the maximum radius used for the search, - “norm”: the normalization factor of the radial function, - “azimuthal_func”: the azimuthal function.

Default is False.