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ring-ll.cpp
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/
ring-ll.cpp
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/***************************************************************/
/* C++ port of meep/examples/ring.ctl, using the */
/* "low-level" meep C++ interface stack, which consists of */
/* libmeep_geom + libctlgeom + libmeep */
/***************************************************************/
/*
; Calculating 2d ring-resonator modes, from the Meep tutorial.
*/
#include <stdio.h>
#include <stdlib.h>
#include <complex>
#include <vector>
#include "meep.hpp"
#include "ctl-math.h"
#include "ctlgeom.h"
#include "meepgeom.hpp"
using namespace meep;
vector3 v3(double x, double y = 0.0, double z = 0.0) {
vector3 v;
v.x = x;
v.y = y;
v.z = z;
return v;
}
/***************************************************************/
/* dummy material function needed to pass to structure( ) */
/* constructor as a placeholder before we can call */
/* set_materials_from_geometry */
/***************************************************************/
double dummy_eps(const vec &) { return 1.0; }
/***************************************************************/
/***************************************************************/
/***************************************************************/
int main(int argc, char *argv[]) {
initialize mpi(argc, argv);
double n = 3.4; // index of waveguide
double w = 1.0; // width of waveguide
double r = 1.0; // inner radius of ring
double height = meep_geom::ENORMOUS;
double pad = 4.0; // padding between waveguide and edge of PML
double dpml = 2.0; // thickness of PML
double sxy = 2.0 * (r + w + pad + dpml); // cell size
double resolution = 10.0;
// (set-param! resolution 10)
// (set! geometry-lattice (make lattice (size sxy sxy no-size)))
grid_volume gv = voltwo(sxy, sxy, resolution);
gv.center_origin();
// (set! symmetries (list (make mirror-sym (direction Y))))
symmetry sym = mirror(Y, gv);
// (set! pml-layers (list (make pml (thickness dpml))))
// ; exploit the mirror symmetry in structure+source:
structure the_structure(gv, dummy_eps, pml(dpml), sym);
// ; Create a ring waveguide by two overlapping cylinders - later objects
// ; take precedence over earlier objects, so we put the outer cylinder first.
// ; and the inner (air) cylinder second.
// (set! geometry (list
// (make cylinder (center 0 0) (height infinity)
// (radius (+ r w)) (material (make dielectric (index n))))
// (make cylinder (center 0 0) (height infinity)
// (radius r) (material air))))
auto material_deleter = [](meep_geom::material_data *m) {
meep_geom::material_free(m);
};
std::unique_ptr<meep_geom::material_data, decltype(material_deleter)> dielectric(
meep_geom::make_dielectric(n*n), material_deleter);
geometric_object objects[2];
vector3 v3zero = {0.0, 0.0, 0.0};
vector3 zaxis = {0.0, 0.0, 1.0};
objects[0] = make_cylinder(dielectric.get(), v3zero, r + w, height, zaxis);
objects[1] = make_cylinder(meep_geom::vacuum, v3zero, r, height, zaxis);
geometric_object_list g = {2, objects};
meep_geom::set_materials_from_geometry(&the_structure, g);
fields f(&the_structure);
// ; If we don't want to excite a specific mode symmetry, we can just
// ; put a single point source at some arbitrary place, pointing in some
// ; arbitrary direction. We will only look for TM modes (E out of the plane).
// (set! sources (list
// (make source
// (src (make gaussian-src (frequency fcen) (fwidth df)))
// (component Ez) (center (+ r 0.1) 0))))
double fcen = 0.15; // ; pulse center frequency
double df = 0.1; // ; df
gaussian_src_time src(fcen, df);
f.add_point_source(Ez, src, vec(r + 0.1, 0.0));
// (run-sources+ 300
// (at-beginning output-epsilon)
// (after-sources (harminv Ez (vector3 (+ r 0.1)) fcen df)))
while (f.round_time() < f.last_source_time())
f.step();
double T = 300.0;
double stop_time = f.round_time() + T;
std::vector<std::complex<double>> fieldData;
vec eval_pt(r + 0.1, 0.0);
while (f.round_time() < stop_time) {
f.step();
fieldData.push_back(f.get_field(Ez, eval_pt));
};
#define MAXBANDS 100
std::complex<double> amp[MAXBANDS];
double freq_re[MAXBANDS];
double freq_im[MAXBANDS];
double err[MAXBANDS];
master_printf("starting do_harminv...\n");
int bands = do_harminv(&fieldData[0], fieldData.size(), f.dt, fcen - 0.5 * df, fcen + 0.5 * df,
MAXBANDS, amp, freq_re, freq_im, err);
master_printf("harminv0: | real(freq) | imag(freq) | Q | abs(amp) | amp "
" | err\n");
master_printf("----------------------------------------------------------------------------------"
"----------\n");
for (int nb = 0; nb < bands; nb++)
master_printf("harminv0: | %.4e | %+.4e | %.4e | %.4e | {%+.2e,%+.2e} | %.1e \n", freq_re[nb],
freq_im[nb], 0.5 * freq_re[nb] / freq_im[nb], abs(amp[nb]), real(amp[nb]),
imag(amp[nb]), err[nb]);
// test comparison with expected values
double err_tol = 1.0e-5;
int ref_bands = 4;
double ref_freq_re[4] = {1.1807e-01, 1.4470e-01, 1.4715e-01, 1.7525e-01};
double ref_freq_im[4] = {-7.5657e-04, -8.9843e-04, -2.2172e-04, -5.0267e-05};
std::complex<double> ref_amp[4] = {std::complex<double>(-6.40e-03,-2.81e-03),
std::complex<double>(-1.42e-04,+6.78e-04),
std::complex<double>(+3.99e-02,+4.09e-02),
std::complex<double>(-1.98e-03,-1.43e-02)};
if (bands != ref_bands) meep::abort("harminv found only %i/%i bands\n", bands, ref_bands);
for (int nb = 0; nb < bands; nb++)
if ((fabs(freq_re[nb] - ref_freq_re[nb]) > 1.0e-2 * fabs(ref_freq_re[nb]) ||
fabs(freq_im[nb] - ref_freq_im[nb]) > 1.0e-2 * fabs(ref_freq_im[nb]) ||
abs(amp[nb] - ref_amp[nb]) > 1.0e-2 * abs(ref_amp[nb])) && (err[nb] < err_tol))
meep::abort("harminv band %i disagrees with ref: {re f, im f, re A, im A}={%e,%e,%e,%e}!= "
"{%e,%e,%e,%e}\n",
nb, freq_re[nb], freq_im[nb], real(amp[nb]), imag(amp[nb]), ref_freq_re[nb],
ref_freq_im[nb], real(ref_amp[nb]), imag(ref_amp[nb]));
master_printf("all harminv results match reference values\n");
// ; Output fields for one period at the end. (If we output
// ; at a single time, we might accidentally catch the Ez field
// ; when it is almost zero and get a distorted view.)
// (run-until (/ 1 fcen) (at-every (/ 1 fcen 20) output-efield-z))
double DeltaT = 1.0 / (20 * fcen);
double NextOutputTime = f.round_time() + DeltaT;
while (f.round_time() < 1.0 / fcen) {
f.step();
if (f.round_time() >= NextOutputTime) {
f.output_hdf5(Ez, f.total_volume());
NextOutputTime += DeltaT;
};
};
// this seems to be necessary to prevent failures
all_wait();
for (int n = 0; n < 2; n++) {
geometric_object_destroy(objects[n]);
}
meep_geom::unset_default_material();
// success if we made it here
return 0;
}